Chromium picolinate supplementation for overweight or obese adults

  • Review
  • Intervention

Authors


Abstract

Background

Obesity is a global public health threat. Chromium picolinate (CrP) is advocated in the medical literature for the reduction of body weight, and preparations are sold as slimming aids in the USA and Europe, and on the Internet.

Objectives

To assess the effects of CrP supplementation in overweight or obese people.

Search methods

We searched The Cochrane Library, MEDLINE, EMBASE, ISI Web of Knowledge, the Chinese Biomedical Literature Database, the China Journal Fulltext Database and the Chinese Scientific Journals Fulltext Database (all databases to December 2012), as well as other sources (including databases of ongoing trials, clinical trials registers and reference lists).

Selection criteria

We included trials if they were randomised controlled trials (RCT) of CrP supplementation in people who were overweight or obese. We excluded studies including children, pregnant women or individuals with serious medical conditions.

Data collection and analysis

Two authors independently screened titles and abstracts for relevance. Screening for inclusion, data extraction and 'Risk of bias' assessment were carried out by one author and checked by a second. We assessed the risk of bias by evaluating the domains selection, performance, attrition, detection and reporting bias. We performed a meta-analysis of included trials using Review Manager 5.

Main results

We evaluated nine RCTs involving a total of 622 participants. The RCTs were conducted in the community setting, with interventions mainly delivered by health professionals, and had a short- to medium-term follow up (up to 24 weeks). Three RCTs compared CrP plus resistance or weight training with placebo plus resistance or weight training, the other RCTs compared CrP alone versus placebo. We focused this review on investigating which dose of CrP would prove most effective versus placebo and therefore assessed the results according to CrP dose. However, in order to find out if CrP works in general, we also analysed the effect of all pooled CrP doses versus placebo on body weight only.

Across all CrP doses investigated (200 µg, 400 µg, 500 µg, 1000 µg) we noted an effect on body weight in favour of CrP of debatable clinical relevance after 12 to 16 weeks of treatment: mean difference (MD) -1.1 kg (95% CI -1.7 to -0.4); P = 0.001; 392 participants; 6 trials; low-quality evidence (GRADE)). No firm evidence and no dose gradient could be established when comparing different doses of CrP with placebo for various weight loss measures (body weight, body mass index, percentage body fat composition, change in waist circumference).

Only three studies provided information on adverse events (low-quality evidence (GRADE)). There were two serious adverse events and study dropouts in participants taking 1000 µg CrP, and one serious adverse event in an individual taking 400 µg CrP. Two participants receiving placebo discontinued due to adverse events; one event was reported as serious. No study reported on all-cause mortality, morbidity, health-related quality of life or socioeconomic effects.

Authors' conclusions

We found no current, reliable evidence to inform firm decisions about the efficacy and safety of CrP supplements in overweight or obese adults.

Résumé scientifique

La supplémentation en picolinate de chrome chez les adultes en surpoids ou obèses

Contexte

L'obésité est une menace de santé publique. Le picolinate de chrome (PCr) est recommandé dans la littérature médicale pour la perte de poids corporel et les préparations sont vendues en tant qu’aides amincissantes aux États-Unis, en Europe et sur Internet.

Objectifs

Évaluer les effets de la supplémentation en PCr chez les personnes en surpoids ou obèses.

Stratégie de recherche documentaire

Nous avons effectué des recherches dans La Bibliothèque Cochrane , MEDLINE, EMBASE, ISI Web of Knowledge, les bases de données de la littérature biomédicale chinoise, Les bases de données du texte intégral du journal de Chine et les bases de données du texte intégral du journal scientifique chinois (toutes les bases de données jusqu' en décembre 2012), ainsi que d'autres sources (y compris les bases de données d'essais en cours, les registres d'essais cliniques et les listes de référence).

Critères de sélection

Nous avons inclus les essais lorsqu’il s’agissait d’essais contrôlés randomisés (ECR) de la supplémentation en PCr chez les patients obèses ou en surpoids. Nous avons exclu les études incluant des enfants, des femmes enceintes ou des patients atteints de graves problèmes médicaux.

Recueil et analyse des données

Deux auteurs ont indépendamment examiné les titres et résumés afin de juger leur pertinence. Les évaluations concernant l’inclusion, l’extraction des données et les risques de biais, ont été effectuées par un auteur et vérifiées par un deuxième. Nous avons considéré le risque de biais en évaluant les domaines de sélection, de performance, d'attrition, de détection et de notification du biais. Nous avons effectué une méta-analyse des essais inclus à l'aide de Review Manager 5.

Résultats principaux

Nous avons évalué neuf ECR portant sur un total de 622 participants. Les ECR ont été menés en milieu communautaire, avec des interventions principalement administrées par les professionnels de santé, qui avaient un suivi à court et moyen terme (jusqu' à 24 semaines). Trois ECR comparaient le PCr plus exercices de musculations ou de résistance par rapport à un placebo plus exercices de musculations ou de résistance, les autres ECR comparaient le PCr seul versus un placebo. Cette revue vise à évaluer quelle dose de PCR pourrait s'avérer plus efficace par rapport à un placebo et par conséquent à évaluer les résultats selon la dose de PCr. Cependant, afin de déterminer si le PCr fonctionne, nous avons également analysé l'effet de toutes les doses de PCr regroupées par rapport à un placebo uniquement sur le poids corporel.

Parmi toutes les doses de PCr étudiées (200 µg, 400 µg, 500 µg, 1 000 µg), nous avons noté que l’effet sur le poids corporel en faveur du PCr était de pertinence clinique discutable après 12 à 16 semaines de traitement : différence moyenne (DM) -1,1 kg (IC à 95%, entre -1,7 et -0,4); P =0,001; 392 participants; 6 essais; preuves de faible qualité (GRADE)). Aucune preuve solide et aucun gradient de dose n'ont pu être établis en comparant les différentes doses de PCr à un placebo pour diverses mesures concernant la perte de poids (poids corporel, indice de masse corporelle, taux de graisse corporelle, changement au niveau du tour de taille).

Seules trois études ont fourni des informations sur les effets indésirables (des preuves de faible qualité (GRADE)). Il s’est avéré deux effets indésirables graves, des sorties d'étude chez les participants prenant 1 000 µg de PCr et un effet indésirable grave chez les patients prenant 400 µg de PCr. Deux participants recevant un placebo ont abandonné en raison d’effets indésirables; un effet était rapporté comme grave. Aucune étude n'avait rendu compte de la mortalité toutes causes confondues, de la morbidité, de la qualité de vie liée à la santé ou des effets socio-économiques.

Conclusions des auteurs

Nous n'avons trouvé aucune preuve courante et fiable pour orienter les décisions définitives concernant l'efficacité et l'innocuité des suppléments en PCr chez des adultes en surpoids ou obèses.

アブストラクト

過体重または肥満の成人に対するピコリン酸クロム補充

背景

肥満は、世界中で公衆衛生を脅かすものとなっている。ピコリン酸クロム(CrP)による減量が医学文献で提唱されており、製剤は、米国や欧州、さらにインターネットで減量薬として販売されている。

目的

過体重または肥満の人を対象にCrP補充の有効性を評価すること。

検索戦略

コクラン・ライブラリ、MEDLINE、EMBASE、ISI Web of Knowledge、Chinese Biomedical Literature Database、China Journal Fulltext DatabaseおよびChinese Scientific Journals Fulltext Database(データベースはいずれも2012年12月まで)を検索し、さらに他の情報源(進行中の試験、臨床試験登録および参考文献リストのデータベースなど)を検索した。

選択基準

過体重または肥満の人を対象に実施されたCrP補充のランダム化比較試験(RCT)とした。小児、妊婦および重篤な疾患のある人を含む試験は除外した。

データ収集と分析

2名の著者が、レビューに関連のある論文タイトルおよび抄録を独立して選別した。1名の著者が、採用の選別、データの抽出および「バイアスのリスク」の評価を行い、2番目のレビューアが確認した。バイアスのリスクは、選択、実行、症例減少、検出および報告の各ドメインを調べて評価した。Review Manager 5を用いて、採用した試験のメタアナリシスを実施した。

主な結果

計622例が参加したRCT 9件を評価した。これらのRCTは地域ベースで実施され、介入は主に医療専門家によって行われ、追跡期間は短~中期(最大24週間)であった。3件のRCTが、CrPとレジスタンストレーニングやウェイトトレーニングの併用を、プラセボとレジスタンストレーニングやウェイトトレーニングの併用と比較し、残るRCTがCrP単独とプラセボを比較した。このレビューでは、プラセボに比較して最も効果のあるCrPの用量に焦点を当てた。このため、結果はCrPの用量毎に評価した。しかし、CrPが全体として効果的であるかどうかを検討するため、CrPの用量をすべてプールしたものとプラセボを比較して、体重に及ぼす効果に限定した解析も行った。

試験で使用されたCrPのあらゆる用量(200 µg、400 µg、500 µg、1000 µg)で、摂取12~16週間後に、臨床的関連性については不明なものの、CrPの効果が体重に対して認められた:平均差(MD)-1.1 kg(95%CI -1.7~-0.4);P=0.001;参加者392例;6試験;質の低いエビデンス(GRADE)。減量のさまざまな指標(体重、肥満指数、体脂肪組成率、腹囲の変化)に関して、CrPの各用量とプラセボを比較しても確かなエビデンスも用量勾配も認められなかった。

有害事象に関する情報を報告した試験はわずか3件であった(質の低いエビデンス(GRADE))。CrP 1000 µgを摂取した参加者に重篤な有害事象および試験からの脱落症例が2例認められ、400 µgを摂取した参加者1例に重篤な有害事象がみられた。プラセボを投与された参加者2例が有害事象のために中止した。有害事象の1件は重篤であると報告されている。全死因死亡率、罹病率、健康関連QOLおよび社会経済的効果に関して報告した試験はなかった。

著者の結論

過体重または肥満の成人を対象としたCrPのサプリメントの有効性および安全性に関して、決定的な答えを導くために必要な信頼できる最新のエビデンスは得られなかった。

訳注

《実施組織》厚生労働省「「統合医療」に係る情報発信等推進事業」(eJIM:http://www.ejim.ncgg.go.jp/)[2016.1.10]
《注意》この日本語訳は、臨床医、疫学研究者などによる翻訳のチェックを受けて公開していますが、訳語の間違いなどお気づきの点がございましたら、eJIM事務局までご連絡ください。なお、2013年6月からコクラン・ライブラリーのNew review, Updated reviewとも日単位で更新されています。eJIMでは最新版の日本語訳を掲載するよう努めておりますが、タイム・ラグが生じている場合もあります。ご利用に際しては、最新版(英語版)の内容をご確認ください。

Plain language summary

Chromium picolinate supplementation for overweight or obese people

Review question

Are chromium supplements useful for reducing body weight in overweight or obese adults?

Background

Chromium is an essential nutrient (trace element) required for the normal metabolism of carbohydrate, protein and fat (i.e. the chemical reactions involved in breaking down these molecules to a form suitable for absorption by the body). Chromium increases the activity of insulin, and dietary supplementation with chromium has produced improvements in glucose metabolism which may lower blood glucose being important for overweight people with diabetes. It is generally believed that chromium may help to reduce a person's weight by decreasing the amount of fat in the body. Chromium is also said to suppress the appetite and stimulate the production of heat by the body, thus increasing energy expenditure. This may contribute to weight loss. Chromium picolinate is one of several chemical compounds of chromium sold as a nutritional supplement as a potential aid to weight loss.

Study characteristics

We included nine randomised controlled trials which compared the efficacy and safety of 8 to 24 weeks of chromium supplementation and placebo in overweight or obese adults (i.e. with a body mass index between 25 and 29.9 kg/m2 defining being overweight and a body mass index of 30kg/m2 or more defining obesity). A total of 622 participants took part in the studies, 346 participants received chromium picolinate and 276 received placebo. The evidence is current to December 2012.

Key results

When the results obtained from the doses of chromium picolinate investigated (200 µg, 400 µg, 500 µg, 1000 µg) were pooled, study participants lost around 1 kg of body weight more than participants receiving placebo. We were unable to find good evidence that this potential weight loss effect increased with increasing dose of chromium picolinate. Only three of nine studies provided information on adverse events, so we were unable to determine whether chromium picolinate supplements are safe and whether any potential harms may increase with dose. In addition, the length of studies included was rather short (maximum of 24 weeks), so we were unable to determine any long-term effects of supplementation. No study reported whether supplementation was associated with increases in deaths from any cause or illnesses (such as myocardial infarction or stroke), or the health-related quality of life or socioeconomic effects of supplementation.

Quality of the evidence

The overall quality of evidence was considered low and we have inadequate information from which to draw conclusions about the efficacy and safety of chromium picolinate supplementation in overweight or obese adults.

Résumé simplifié

La supplémentation en picolinate de chrome chez les adultes en surpoids ou obèses

Question de la revue

Les suppléments de chrome sont-ils utiles pour réduire le poids corporel chez des adultes en surpoids ou obèses ?

Contexte

Le chrome est un nutriment essentiel (oligo-élément) nécessaire pour réguler le métabolisme en glucides, en protéines et en graisses (par exemple, les réactions chimiques impliquées dans la dissociation des molécules en une forme appropriée pour l'absorption par le corps). Le chrome augmente l'activité de l'insuline et les suppléments alimentaires à base de chrome ont donné lieu à des améliorations dans le métabolisme au niveau du glucose, ce qui pourrait diminuer la glycémie, importante lors de surpoids chez les patients atteints de diabète. Il est généralement admis que le chrome peut aider une personne à perdre du poids en diminuant la quantité de graisses dans le corps. Le chrome engendrerait également une perte d'appétit et stimulerait la production de chaleur par le corps, augmentant la dépense énergétique. Cela pourrait contribuer à la perte de poids. Le picolinate de chrome fait partie de plusieurs substances chimiques composées de chrome et vendu en tant que supplément nutritionnel comme un aide potentielle à la perte de poids.

Les caractéristiques de l'études

Nous avons inclus neuf essais contrôlés randomisés qui comparaient, pendant une durée de 8 à 24 semaines, l'efficacité et l'innocuité de la supplémentation en chrome par rapport à un placebo chez des adultes en surpoids ou obèses (avec un indice de masse corporelle entre 25 et 29,9kg/m 2 définissant le surpoids et un indice de masse corporelle 30kg/m 2 définissant l'obésité). Les études comprenaient un total de 622 participants, dont 346 recevaient le picolinate de chrome et 276 recevaient un placebo. Les preuves sont à jour en décembre 2012.

Résultats principaux

Lorsque les résultats obtenus à partir des doses de picolinate de chrome (200 µg, 400 µg, 500 µg, 1 000 µg) ont été regroupés, les participants avaient perdu environ 1 kg de poids corporel, plus que les participants ayant reçu un placebo. Nous n'avons pas trouvé de preuve solide démontrant que la perte de poids augmentait avec une dose de picolinate de chrome plus élevée. Seuls trois des neuf études ont fourni des informations sur les effets indésirables, nous ne sommes donc pas parvenus à déterminer si les suppléments en picolinate de chrome sont sûrs et si tout préjudice potentiel peut s’aggraver avec la dose. De plus, la durée des études incluses était relativement courte (maximum de 24 semaines), nous ne sommes donc pas parvenus à déterminer les effets à long terme de la supplémentation. Aucune étude n'avait rendu compte si la supplémentation était associée à une augmentation de décès toutes causes confondues ou de maladies (telles que l'infarctus du myocarde ou l'AVC), ou les effets de la supplémentation sur la qualité de vie liée à la santé ou les effets socio-économique.

Qualité des preuves

La qualité globale des preuves a été considérée comme faible et nous n’avons pas suffisamment d’informations pour fournir des conclusions concernant l'efficacité et l'innocuité de la supplémentation en picolinate de chrome chez des adultes en surpoids ou obèses.

Notes de traduction

Traduit par: French Cochrane Centre 1st November, 2013
Traduction financée par: Financeurs pour le Canada : Instituts de Recherche en Santé du Canada, Ministère de la Santé et des Services Sociaux du Québec, Fonds de recherche du Québec-Santé et Institut National d'Excellence en Santé et en Services Sociaux; pour la France : Ministère en charge de la Santé

Laički sažetak

Krom pikolinat kao dodatak prehrani za osobe s prekomjernom  tjelesnom težinom ili za pretile osobe

Istraživačko pitanje

Jesu li dodaci prehrani koji sadrže krom korisni za smanjenje tjelesne težine kod odraslih osoba s prekomjernom težinom i pretilih?

Dosadašnje spoznaje

Krom je esencijalan nutrijent (element u tragovima) koji je potreban za normalan metabolizam ugljikohidrata, proteina i masti (odnosno kemijsku reakciju razbijanja tih molekula u formu koja je pogodna za apsorpciju u tijelu). Krom povećava aktivnost inzulina, i utvrđeno je da dodatak prehrani koji sadrži krom može poboljšati metabolizam glukoze; to može smanjiti razinu glukoze u krvi što je važno za pretile osobe s dijabetesom. Općenito se vjeruje da krom može smanjiti tjelesnu težinu osobe tako da smanjuje količinu masti u tijelu. Za krom se također smatra da potiskuje apetit i stimulira proizvodnju topline u tijelu gdje se povećava potrošnja energije To može doprinijeti gubitku tjelesne težine. Kromov pikolinat je jedan od nekoliko kemijskih spojeva kroma koji se prodaje kao dodatak prehrani koji navodno pomaže u mršavljenju

Značajke istraživanja

U ovaj Cochrane sustavni pregled uključeno je devet randomiziranih kontroliranih ispitivanja kojima je uspoređena djelotvornost i sigurnost primjene dodataka kroma i placeba kod prekomjerne težine i pretilih odraslih osoba u periodu od 8.-og do 24.-og tjedna (pri čemu je prekomjerna tjelesna težina definirana indeksom tjelesne mase između 25 i 29.9 kg/m2 a pretilost kao indeksa+ tjelesne mase od 30 kg/m2 ili više). U studijama je ukupno sudjelovalo 622 ispitanika, od čega je 346 ispitanika dobilo kromov pikolinat, a 276 je dobilo placebo. Dokazi se odnose na literaturu objavljenu do prosinca 2012. godine.

Ključni rezultati

Kad su zajednički analizirani svi rezultati ispitanih doza kromovog pikolinata dobiveni ( 200 μg, 400 μg, 500 μg, 1000 μg), ispitanici koji su primali kromov pikolinat izgubili su oko 1 kg više od ispitanika koji su primali placebo. Nije bilo moguće pronaći dobar dokaz da se taj potencijalni učinak gubitka težine povećava s povećanjem doze kromovog pikolinata. Samo su tri od devet studija navele informacije o nuspojavama tako da nije bilo moguće utvrditi je li dodatak kromovog pikolinata siguran i je li se može bilo koja potencijalna šteta povećati s većom dozom. Osim toga, uključene studije vrlo su kratko trajale (najviše 24 tjedna ), tako da nije bilo moguće utvrditi dugoročne učinke kod primjene tih dodataka. Nijedna studija nije prikazala je li dodatak povezan s povećanjem smrti zbog bilo kojeg uzroka ili bolesti (kao što su srčani infarkt ili moždani udar ), ili kvalitete života povezane sa zdravljem i socioekonomskim efektom.

Kvaliteta dokaza

Ukupna kvaliteta dokaza ocijenjena je kao niska, zbog čega raspoložive inforamacije nisu pouzdan izvor iz kojeg možemo izvući zaključke o djelotvornosti i sigurnosti dodataka kromovog pikolinata za mršavljenje kod prekomjerne težine ili pretilih odraslih osoba.

Bilješke prijevoda

Hrvatski Cochrane
Prevela: Ana Tokić
Ovaj sažetak preveden je u okviru volonterskog projekta prevođenja Cochrane sažetaka. Uključite se u projekt i pomozite nam u prevođenju brojnih preostalih Cochrane sažetaka koji su još uvijek dostupni samo na engleskom jeziku. Kontakt: cochrane_croatia@mefst.hr

平易な要約

過体重または肥満の人に対するピコリン酸クロム補充

レビューの論点

クロミウムのサプリメントは過体重または肥満の成人の減量に有用か。

背景

クロミウムは、炭水化物、蛋白および脂質の正常な代謝(これらの分子を体が吸収するのに適した形に分解する化学反応)に必要な必須栄養素(微量元素)である。クロミウムはインスリンの活性を高める。したがって、クロミウムを補充することによって糖代謝が改善する。これは、糖尿病で過体重の人にとって重要な血糖値の低下につながる可能性がある。クロミウムは、一般に、体内の脂肪の量を減らすことによって減量に効果を発揮するのではないかと考えられている。クロミウムは、ほかにも、食欲を抑制し、体の熱産生を促進させることにより、エネルギーの消費量を増加させると考えられている。これが減量に寄与する可能性がある。ピコリン酸クロムは、減量に役立つ可能性がある栄養剤として販売されている数種類のクロミウム化合物のひとつである。

研究の特性

過体重または肥満の成人(肥満指数が25~29.9 kg/m2を過体重、肥満指数が30 kg/m2以上を肥満と定義した)を対象に、8~24週間のクロミウム補充の有効性および安全性をプラセボと比較したランダム化比較試験(RCT)9件を採用した。 これらの試験には、計622例が参加した。346例がピコリン酸クロムを摂取し、276例にはプラセボが投与された。本エビデンスは2012年12月現在のものである。

主な結果

試験に用いられたピコリン酸クロムの各用量(200 µg、400 µg、500 µg、100 0µg)の結果を統合したところ、プラセボを投与された参加者よりも、体重が1 kg前後減少していた。この潜在的な減量効果が、ピコリン酸クロムの用量が増えるにつれて大きくなることを示す良質のエビデンスは発見されなかった。9件の試験のうち、有害事象に関して報告していたのはわずか3件であったため、ピコリン酸クロムのサプリメントが安全であるかどうか、さらに、増量に伴って有害性が大きくなる可能性があるかどうかを明らかにすることはできなかった。さらに、採用した試験がいくぶん短期間であったため(最大24週間)、長期間の補充による影響を明らかにすることはできなかった。ピコリン酸クロムの補充が、全死因死亡率、罹病率(心筋梗塞や脳卒中)の増加や、健康関連QOLおよび社会経済的効果に関連があるかどうかを報告した試験はなかった。

エビデンスの質

エビデンスの質は全体的に低いと判定した。過体重または肥満の成人に対するピコリン酸クロム補充の有効性および安全性について、結論を導くには情報が不十分である。

訳注

《実施組織》厚生労働省「「統合医療」に係る情報発信等推進事業」(eJIM:http://www.ejim.ncgg.go.jp/)[2016.1.10]
《注意》この日本語訳は、臨床医、疫学研究者などによる翻訳のチェックを受けて公開していますが、訳語の間違いなどお気づきの点がございましたら、eJIM事務局までご連絡ください。なお、2013年6月からコクラン・ライブラリーのNew review, Updated reviewとも日単位で更新されています。eJIMでは最新版の日本語訳を掲載するよう努めておりますが、タイム・ラグが生じている場合もあります。ご利用に際しては、最新版(英語版)の内容をご確認ください。

Streszczenie prostym językiem

Suplementy z pikolinianem chromu dla osób dorosłych z nadwagą lub otyłością

Pytanie badawcze

Czy suplementy chromu są pomocne w zmniejszaniu masy ciała u osób dorosłych z nadwagą lub otyłych?

Wprowadzenie

Chrom jest niezbędnym składnikiem odżywczym (mikroelementem), koniecznym do prawidłowego metabolizmu węglowodanów, białek i tłuszczy (tzn. reakcji chemicznych biorących udział w rozkładaniu tych cząsteczek do postaci nadającej się do wchłaniania przez organizm). Chrom wzmaga aktywność insuliny, stąd suplementacja diety chromem prowadziła do poprawy metabolizmu glukozy, mogącego skutkować zmniejszeniem stężenia glukozy we krwi, co z kolei jest istotne dla osób z nadwagą i cukrzycą. Powszechnie się uważa, że chrom może się przyczynić się do spadku masy ciała, zmniejszając ilość tłuszczu w organizmie. Temu mikroelementowi przypisuje się również właściwość zmniejszania apetytu i pobudzanie wytwarzania ciepła w organizmie, a tym samym zwiększanie wydatkowania energii. Te procesy mogą przyczynić się do zmniejszenia masy ciała. Pikolinian chromu jest jednym z wielu związków chromu sprzedawanych jako suplement wspomagający utratę masy ciała.

Charakterystyka badania

Do niniejszego przeglądu zakwalifikowano 9 badań z randomizacją. Porównywano w nich skuteczność oraz bezpieczeństwo suplementacji chromem z placebo, przez okres od 8 do 24 tygodni, u osób dorosłych z nadwagą lub otyłością (osoby ze wskaźnikiem masy ciała pomiędzy 25 a 29,9 kg/m 2 klasyfikowano jako mające nadwagę, a te ze wskaźnikiem masy ciała równym lub powyżej 30 kg/m 2 - jako otyłe). Łącznie w analizowanych badaniach wzięło udział 622 uczestników: 346 otrzymywało pikolinian chromu, a 276 - placebo. Dane są aktualne do grudnia 2012.

Główne wyniki

Połączenie wyników uzyskanych w badaniach nad stosowaniem pikolinianu chromu w różnych dawkach (200 µg, 400 µg, 500 µg, 1000 µg), pozwoliło stwierdzić, że uczestnicy badań, otrzymujący chrom stracili około 1 kg masy ciała więcej w porównaniu z osobami stosującymi placebo. Nie udało się jednak znaleźć wystarczających danych, by stwierdzić, że spadek masy ciała był związany ze zwiększeniem dawki pikolinianu chromu. Jedynie 3 z 9 analizowanych badań dostarczały informacji na temat działań niepożądanych, nie było więc możliwe ustalenie, czy suplementy pikolinianu chromu są bezpieczne, i czy ewentualne szkody mogą się nasilać wraz ze zwiększaniem dawki. Ponadto, włączone do przeglądu badania trwały stosunkowo krótko (maksymalnie 24 tygodnie), nie było więc możliwe określenie żadnych długofalowych skutków suplementacji. W żadnym z badań nie podano, czy suplementacja wiązała się ze zwiększeniem liczby zgonów z jakiejkolwiek przyczyny lub spowodowanych chorobami (takimi jak zawał serca czy udar mózgu), bądź poprawą jakości życia związanej ze zdrowiem albo skutkami społeczno-ekonomicznymi.

Jakość danych

Ogólnie jakość danych oceniono jako niską. Przedstawione dane nie są wystarczające, aby można było wyciągnąć wnioski co do skuteczności i bezpieczeństwa stosowania suplementacji pikolinianem chromu u osób dorosłych z nadwagą lub otyłością.

Uwagi do tłumaczenia

Tłumaczenie Joanna Zając Redakcja Ewa Płaczkiewicz-Jankowska

Summary of findings(Explanation)

Summary of findings for the main comparison. 
  1. aDowngraded by two levels owing to high risk of performance and detection bias, and inadequate reporting in most of the included studies

    bDowngraded by two levels owing to indirectness and conflicting evidence between different studies of various doses of chromium picolinate and duration of treatment

Chromium picolinate supplementation for overweight or obese adults

Population: overweight or obese adults

Settings: community volunteers and outpatients

Intervention: chromium picolinate

Comparison: placebo

OutcomesRelative / absolute effect(s)
(95% CI)
No of participants
(studies)
Quality of the evidence
(GRADE)
Comments
Health-related quality of lifeSee commentSee commentSee commentNot investigated

Adverse events

Follow-up: 8 weeks to 6 months

2 serious adverse events and study dropouts after 1000 µg chromium picolinate (2/15 participants); 1 serious adverse event after 400 µg chromium picolinate (1/39 participants); 1 serious adverse event (1/18 participants) and 2 study dropouts on placebo (2/58 participants)

189

(3)

⊕⊕⊝⊝
lowa
Only 3/9 studies provided information on adverse events
Death from any causeSee commentSee commentSee commentNot investigated
MorbiditySee commentSee commentSee commentNot investigated

Weight loss [kg]

Follow-up: 12 to 16 weeks

-1.1 (-1.7 to -0.4)

392

(6)

⊕⊕⊝⊝
lowb
All chromium picolinate doses were pooled
Socioeconomic effectsSee commentSee commentSee commentNot investigated
*The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% CI) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI).
CI: confidence interval; RR: risk ratio
GRADE Working Group grades of evidence
High quality: Further research is very unlikely to change our confidence in the estimate of effect.
Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.
Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.
Very low quality: We are very uncertain about the estimate.

Background

Description of the condition

Obesity and overweight are common global health conditions. The prevalence of obesity and overweight has increased considerably in both developing and developed countries. The World Health Organization (WHO) have estimated that, globally in 2005, approximately 1.6 billion adults (aged 15 years or older) were overweight and that at least 400 million adults were obese (WHO 2006). The WHO projects that, by 2015, approximately 2.3 billion adults will be overweight and more than 700 million will be obese. Obesity is defined as the degree of fat storage associated with elevated health risks. However, because fat mass is difficult to measure, the pragmatic definition of obesity is based on body mass index (BMI). The WHO guidelines define a BMI of 18.5 to 24.9 kg/m2 as normal, 25 to 29.9 kg/m2 as grade 1 overweight and greater than 30 kg/m2 as grade 2 overweight (obesity) (WHO 1995).

Obesity is a concern because of its implications for the health of an individual, as it increases the risk of many diseases and health conditions, including coronary heart disease (Rimm 1995; Whitlock 2002), type 2 diabetes (Colditz 1995), hypertension, dyslipidaemia (Denke 1994), sleep apnoea and respiratory problems (Naimark 1960).

Description of the intervention

Chromium is an essential trace element required for the normal metabolism of carbohydrate, protein and fat. Chromium is a cofactor necessary for the activity of insulin, and dietary supplementation with chromium has produced modest improvements in glucose metabolism, insulin sensitivity and body composition in human trials (Drake 2012). Organic chromium is a compound of trivalent chromium and it assists in efficient chromium absorption. Chromium picolinate (CrP) is advocated in the medical literature for the reduction of body weight (Murray 1998; Pizzorno 1999) and preparations are sold as slimming aids in the USA and Europe, and on the Internet.

Adverse effects of the intervention

In a narrative review, most of the reported side effects of CrP supplementation were non-specific and the most frequent complaints were watery stools, weakness, dizziness, headaches, nausea and vomiting (Kleefstra 2006). Overall, chromium was well tolerated. There were no serious adverse events. Also, the number of individuals reporting adverse events in the supplemented groups was not significantly different from that in placebo groups (John 2007; Stephen 2008).

How the intervention might work

It is generally believed that chromium may exert its effects on weight loss by decreasing fat levels in the body and through insulin-sensitising effects. CrP has been suggested to impact on neurotransmitters involved in the regulation of eating behaviour, mood and food cravings (Docherty 2005). Chromium may suppress the appetite and stimulate thermogenesis through sensitisation of insulin-sensitive glucoreceptors in the brain (Wang 2007). Body fat distribution is related to insulin sensitivity; peripheral fat is more insulin-sensitive than central fat found in the chest and abdomen (Kahn 2006).

Why it is important to do this review

Chromium may improve impaired glucose tolerance, reduce elevated blood lipid concentrations, and result in weight loss and improved body composition in some individuals, but results have been equivocal (Volpe 2001). A meta-analysis of 10 double-blind, placebo-controlled trials provided evidence of a relatively small reduction in body weight in overweight and obese individuals receiving CrP (Pittler 2003). However, because of the limited number of trials and participants, the clinical relevance of this effect is debatable and a lack of robustness means that the results have to be interpreted with caution. Since the publication of this meta-analysis, the results of many studies including large numbers of individual shave become available. A systematic review of all available randomised controlled trials (RCTs) is needed, which could help clinicians, individuals and others decide whether chromium is a useful weight loss tool for overweight and obese individuals.

Objectives

To assess the effects of CrP supplementation in overweight or obese people.

Methods

Criteria for considering studies for this review

Types of studies

Randomised controlled trials (RCTs).

Types of participants

Adults (aged 18 years and older) defined as overweight or obese at baseline. We excluded studies including children, pregnant women or individuals with serious medical conditions.

Diagnostic criteria

Adults with a BMI between 25 and 29.9 kg/m2 were considered overweight; those with a BMI of 30 kg/m2 or higher were considered obese.

Types of interventions

We investigated the following comparisons of the intervention versus controls/comparators where the same letters indicate direct comparisons.

Intervention
  • (a) Chromium picolinate (CrP)

  • (b) CrP plus another treatment

Comparator

(a1) Placebo

(a2) Different CrP dosage

(b) Placebo plus another treatment

Concomitant treatments (e.g. diet or exercise) had to be identical between intervention and control groups.

Types of outcome measures

Primary outcomes
  • Weight loss (e.g. BMI, waist circumference, percentage body fat).

  • Adverse events (e.g. gastrointestinal, nervous system, metabolism).

  • Health-related quality of life (measured with a validated instrument).

Secondary outcomes
  • Death from any cause.

  • Morbidity (e.g. cardiovascular outcomes such as myocardial infarction or stroke).

  • Blood pressure.

  • Lipids (e.g. total cholesterol, HDL-C, LDL-C and triglycerides).

  • Fasting blood glucose.

  • Socioeconomic effects.

Timing of outcome measurement
  • Short-term: one to six weeks.

  • Medium-term: more than 6 weeks to 12 weeks.

  • Long-term: more than 12 weeks.

Search methods for identification of studies

Electronic searches

We searched the following sources from inception to the specified date to identify trials:

  • The Cochrane Library (Issue 10, 2012).

  • MEDLINE (to December 2012).

  • EMBASE (to December 2012).

  • ISI Web of Knowledge (to December 2012).

  • Chinese Biomedical Literature Database (CBM) (to December 2012).

  • China Journal full-text database (to December 2012).

  • Chinese Scientific Journals full-text database (to December 2012).

We also searched databases of ongoing trials (www.ClinicalTrials.gov/) and the Current Controlled Trials metaRegister (www.controlled-trials.com/).

For detailed search strategies please see Appendix 1 (searches were not older than six months at the moment the final review draft was checked into the Cochrane Information Management System for editorial approval). We used PubMed's 'My NCBI' (National Center for Biotechnology Information) email alert service for the identification of newly published studies using a basic search strategy (see Appendix 1).

If we detected additional key words of relevance during any of the electronic or other searches we planned to modify the electronic search strategies to incorporate these terms. We included studies published in any language.

Searching other resources

We tried to identify other potentially eligible trials or ancillary publications by searching the reference lists of retrieved included trials, (systematic) reviews, meta-analyses and health-technology assessment reports.

Data collection and analysis

Selection of studies

To identify the studies to be assessed further, two review authors (TH, GX) independently scanned the abstract or title, or both, of every record retrieved. We investigated the full text of all potentially relevant articles. Where there were differences in opinion between authors, these were resolved by a third author (ZZ). If resolution of disagreement was not possible, we intended to add the article to those 'awaiting assessment' and we contacted the trial authors for clarification. We present an adapted PRISMA (preferred reporting items for systematic reviews and meta-analyses) flow-chart showing the process of study selection (Figure 1) (Liberati 2009).

Figure 1.

Study flow diagram.

Data extraction and management

For studies that fulfilled the inclusion criteria, two authors (TH, HZ) independently extracted relevant population and intervention characteristics using standard data extraction templates (for details see Table 1 and Appendix 2; Appendix 3; Appendix 4; Appendix 5; Appendix 6; Appendix 7; Appendix 8; Appendix 9); any disagreements were resolved by discussion or, if required, by a third author.

Table 1. Overview of study populations
  1. aDuration of intervention and/or follow-up under randomised conditions until end of study

    "-" denotes not reported

    C: control; CrP: chromium picolinate; I: intervention; ITT: intention-to-treat; RT: resistance training

Characteristic

Study ID

Intervention(s) and control(s)[N]
Screened /
eligible
[N]
Randomised
[N]
Safety
[N]
ITT
[N]
Finishing study
[%]
Randomised
finishing study
Follow-upa
1. Kaats 1996I1: CrP 200 μg/day2333333-3310072 days
I2: CrP 400 μg/day6666-66100
C: placebo5555-55100
total:154154-154100 
2. Kaats 1998I: CrP 400 μg/day1306262-6210090 days
C: placebo6060-60100
total:122122-122100 
3. Joseph 1999I: CrP 1000 μg/day + RT351717-1710012 weeks
C: placebo + RT1515-15100
total:3232-32100 
4. Kleefstra 2006I1: CrP 500 μg/day601919-17896 months
I2: CrP 1000 μg/day1717-1482
C: placebo1717-1588
total:5353-4687 
5. Iqbal 2009I: CrP 500 μg/day153333328288416 weeks
C: placebo3030292996
total:6363575790 
6. Volpe 2001I: CrP 400 μg/day + weight training442222-209112 weeks
C: placebo + weight training2222-1777
total:4444-3784 
7. Anton 2008I: CrP 400 μg/day992828-19688 weeks
C: placebo2828-2175
total:5656-4071 
8. Campbell 1999I: CrP 1000 μg/day + RT2399-910013 weeks
C: placebo + RT99-9100
total:1818-18100 
9. Yazaki 2010I: CrP 400 μg/day1564040-307524 weeks
C: placebo4040-2870
total:8080-5872 
Grand total All interventions   346  320 93 
All controls 276 256 93
All interventions and controls 622 576 93

We sent an email request to contact authors of published studies to enquire whether they were willing to answer questions regarding their trials. We published the results of this survey in Appendix 10. Thereafter, we sought relevant missing information on the trial from the original author(s) of the article, if required.

We planned to provide information, including the trial identifier, about potentially relevant ongoing studies in the table 'Characteristics of ongoing studies'. We also intended to include specific data from the protocol of each included study, obtained from databases of ongoing trials or from publications of study designs, or both, in Appendix 6 ('Matrix of study endpoints (protocol/trial documents)').

Dealing with duplicate publications and companion papers

In the case of duplicate publications and companion papers of a primary study, we tried to maximise the yield of information by the simultaneous evaluation of all available data.

Assessment of risk of bias in included studies

Two authors (TH, JL) assessed each trial independently. We resolved possible disagreements by consensus, or by consultation with a third author (ZZ). In cases of disagreement, we consulted the rest of the group and made a judgement based on consensus.

We assessed risk of bias using The Cochrane Collaboration’s tool (Higgins 2011; Higgins 2011a) and adopted the following bias criteria.

  • Random sequence generation (selection bias).

  • Allocation concealment (selection bias).

  • Blinding (performance bias and detection bias), separated for blinding of participants and personnel and blinding of outcome assessment.

  • Incomplete outcome data (attrition bias).

  • Selective reporting (reporting bias) - see Appendix 5.

  • Other bias.

We judged 'Risk of bias' criteria as low, high or unclear, and evaluated individual bias items as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011). We present a 'Risk of bias' figure and a 'Risk of bias summary' figure.

We assessed the impact of individual bias domains on study results at endpoint and study levels.

For performance bias (blinding of participants and personnel), detection bias (blinding of outcome assessors) and attrition bias (incomplete outcome data) we intended to evaluate risk of bias separately for subjective and objective outcomes.

We defined the following endpoints as subjective outcomes.

  • Adverse events.

  • Health-related quality of life.

We defined the following outcomes as objective outcomes.

  • Weight loss.

  • Death from any cause.

  • Blood pressure.

  • Lipids.

  • Fasting blood glucose.

  • Socioeconomic effects.

Measures of treatment effect

We expressed dichotomous data as odds ratios (ORs) or risk ratios (RRs) with 95% confidence intervals (CIs). We expressed continuous data as mean differences (MDs) with 95% CIs.

Unit of analysis issues

We took into account the level at which randomisation occurred, such as cross-over trials, cluster-randomised trials and multiple observations for the same outcome.

Dealing with missing data

We tried our best to obtain relevant missing data from authors if feasible, and carefully performed evaluations of important numerical data, such as screened, randomised participants as well as intention-to-treat (ITT), as-treated and per-protocol (PP) populations. We investigated attrition rates (e.g. dropouts, losses to follow-up and withdrawals), and critically appraised issues of missing data and imputation methods (e.g. last observation carried forward (LOCF)).

Assessment of heterogeneity

In the event of substantial clinical, methodological or statistical heterogeneity, our intention was not to report study results as meta-analytically pooled effect estimates.

We identified heterogeneity by visual inspection of the forest plots and by using a standard Chi2 test with a significance level of α = 0.1, in view of the low power of this test. We specifically examined heterogeneity using the I2 statistic, which quantifies inconsistency across studies to assess the impact of heterogeneity on the meta-analysis (Higgins 2002; Higgins 2003), where an I2 statistic of 75% or more indicates a considerable level of inconsistency (Higgins 2011).

If heterogeneity was found, we intended to attempt to determine potential reasons for it by examining individual study and subgroup characteristics.

We expected the following characteristics to introduce clinical heterogeneity:

  • Sex.

  • Age.

  • Chromium doses.

  • Body mass index (BMI).

  • Duration of treatment.

Assessment of reporting biases

We planned to use funnel plots when we included 10 or more studies for a given outcome, in order to assess small study effects. As there could be several explanations for funnel plot asymmetry we planned to interpret results carefully (Sterne 2011).

Data synthesis

We planned, unless there was good evidence for homogeneity across studies, to primarily summarise data at low risk of bias by means of a random-effects model (Wood 2008). We intended to interpret random-effects meta-analyses giving due consideration to the whole distribution of effects, ideally by presenting a prediction interval (Higgins 2009). A prediction interval specifies a predicted range for the true treatment effect in an individual study (Riley 2011). In addition, we performed statistical analyses according to the statistical guidelines contained in the newest version of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011).

Subgroup analysis and investigation of heterogeneity

We planned to carry out the following subgroup analyses of our primary outcome parameter(s) (see above) and investigate any interactions:

  • Dose (depending on data).

  • Duration of intervention (depending on data).

Sensitivity analysis

We planned to perform sensitivity analyses in order to explore the influence of the following factors on effect sizes.

  • Restricting the analysis to published studies.

  • Restricting the analysis, taking into account risk of bias, as specified above.

  • Restricting the analysis to very long or large studies to establish how much they dominate the results.

  • Restricting the analysis to studies using the following filters: diagnostic criteria, language of publication, source of funding (industry versus other), and country.

We also planned to test the robustness of the results by repeating the analysis using different measures of effect size (RR, OR etc.) and different statistical models (fixed-effect and random-effects models).

Results

Description of studies

For a detailed description of studies, see the 'Characteristics of included studies' and 'Characteristics of excluded studies' sections.

Results of the search

The initial search identified 359 records; from these, 25 full text papers were identified for further examination. We excluded the other studies on the basis of their titles or abstracts because they did not meet the inclusion criteria, were not relevant to the question under study or were a duplicate report (see Figure 1). After screening the full text of the selected publications, nine studies (nine publications) met the inclusion criteria. All studies were published in English. We contacted all authors of included studies and received no reply.

Included studies

A detailed description of the characteristics of included studies is presented elsewhere (see 'Characteristics of included studies' and Appendix 2; Appendix 3; Appendix 4; Appendix 5; Appendix 6; Appendix 7; Appendix 8; Appendix 9).

The following is a succinct overview.

Comparisons

Three studies evaluated CrP plus resistance training (RT) or weight training versus placebo with RT or weight training (Campbell 1999; Joseph 1999; Volpe 2001). The other studies investigated CrP alone versus placebo.

Overview of study populations

A total of 622 participants were included in the nine trials, 346 participants were randomised to CrP and 276 to placebo. A total of 320 (93%) participants receiving CrP and 256 (93%) participants receiving placebo finished the study.The individual total sample sizes ranged from 18 to 154.

Study design

All studies were RCTs. All trials adopted a parallel-group superiority design and all used a placebo control. No trial was multicentred. In terms of blinding, five studies were double-blinded for participants and personnel (Joseph 1999; Kaats 1996; Kaats 1998; Kleefstra 2006; Yazaki 2010). Outcome assessors were blinded in four studies (Joseph 1999; Kaats 1996; Kaats 1998; Kleefstra 2006). Studies were performed between the years 1996 and 2010. The duration of interventions ranged from eight weeks to six months, with a mean study period of 12 weeks. Only two trials had a duration of intervention longer than 24 weeks (Kleefstra 2006; Yazaki 2010); durations in the other trials were 16 weeks (Iqbal 2009), 12 weeks (Campbell 1999; Joseph 1999; Volpe 2001), 10 weeks (Kaats 1996), 13 weeks (Kaats 1998) and 8 weeks (Anton 2008).

Settings

All of the studies were conducted in the USA. Two studies had an outpatient setting (Kleefstra 2006; Iqbal 2009); the other studies included community volunteers.

Participants

The participating population comprised overweight and obese adults only (see Appendix 3 and Appendix 4). Females were recruited more often than males in four trials (Iqbal 2009; Kaats 1996; Kaats 1998; Kleefstra 2006); one trial recruited more male than female participants (Joseph 1999). Two trials included only women (Anton 2008; Volpe 2001) and one trial only men (Campbell 1999). Four trials reported age as a range of values (Campbell 1999; Iqbal 2009; Volpe 2001; Yazaki 2010), whereas five trials reported age as a mean value (Anton 2008; Joseph 1999; Kaats 1996; Kaats 1998; Kleefstra 2006). All trials included participants from economically developed countries. Two trials reported the ethnic proportion of participants (Anton 2008; Iqbal 2009). One trial included participants with diabetes mellitus reporting insulin treatment before the start of the trial (Kleefstra 2006). Across all studies, mean baseline BMI at baseline ranged from 28.4 to 37.8 kg/m2.

No trial reported participant comorbidities, six trials provided detail about cointerventions in participants (Anton 2008; Campbell 1999; Joseph 1999; Kaats 1998; Volpe 2001; Yazaki 2010) and one trial provided details of the concomitant medications used by participants (Kleefstra 2006). Criteria for entry into the individual studies are outlined in the 'Characteristics of included studies' section.

Diagnosis

Participants were diagnosed as overweight or obese according to BMI criteria. In all the studies, participants had a BMI greater than 25 kg/m2.

Interventions

No study had a titration period. CrP was applied by the oral route and varied in dosing schedule between one and two times a day. The daily dose of chromium varied between 0.4 mg and 1 mg, with an average daily dose of 0.5 mg. All studies used a matching placebo as the control intervention.

Outcomes

All studies explicitly stated a primary endpoint in the publication; five studies also stated secondary endpoints (Anton 2008; Iqbal 2009; Kleefstra 2006; Volpe 2001; Yazaki 2010).

Reporting of endpoints

BMI was measured in four studies (Iqbal 2009; Joseph 1999; Kleefstra 2006; Yazaki 2010), weight was measured in six studies (Anton 2008; Campbell 1999; Joseph 1999; Kaats 1996; Kaats 1998; Volpe 2001). Body fat (as a percentage) was measured in six studies (Campbell 1999; Joseph 1999; Kaats 1996; Kaats 1998; Volpe 2001; Yazaki 2010). Waist circumference was measured in three studies (Iqbal 2009; Joseph 1999; Volpe 2001). Lipids were measured in four studies (Iqbal 2009; Kleefstra 2006; Volpe 2001; Yazaki 2010). Fasting glucose was measured in four studies (Anton 2008; Iqbal 2009; Volpe 2001; Yazaki 2010). Three studies reported adverse events (Anton 2008; Kleefstra 2006; Yazaki 2010). Two studies assessed food intake (Anton 2008; Volpe 2001), and two studies assessed muscle size, and strength or power development during the trial (Campbell 1999; Volpe 2001).

No studies investigated death from any cause, health-related quality of life or the socioeconomic effects of treatment. For a summary of all outcomes assessed in each study, see Appendix 5.

Excluded studies

Sixteen publications were excluded after careful evaluation of the full-text article (Albarracin 2008; Bunting 1994; Diaz 2008; Docherty 2005; Earle 1989; Geohas 2007; Hoeger 1998; Joyal 2004; Pasman 1997; Pittler 2004; Rabinowitz 1983; Stupar 1999; Trent 1995; Wang 2010; Wilson 1995; Zenk 2007) - see Figure 1.

The reasons for exclusion were: intervention and control not comparable (Albarracin 2008; Diaz 2008; Geohas 2007; Hoeger 1998; Zenk 2007), study design (Bunting 1994; Joyal 2004; Pasman 1997; Pittler 2004; Stupar 1999; Wang 2010) and participants not being obese or overweight (Docherty 2005; Earle 1989; Rabinowitz 1983; Trent 1995; Wilson 1995). For further details, see 'Characteristics of excluded studies'.

Risk of bias in included studies

For details on the risk of bias of included studies see 'Characteristics of included studies'. For an overview of review authors' judgements about each 'Risk of bias' item for individual studies and across all studies, see Figure 2 and Figure 3. We investigated performance bias, detection bias and attrition bias separately for objective and subjective outcome measures. We defined weight loss (e.g. BMI, waist circumference, percentage body fat); blood pressure; lipids (e.g. total cholesterol, HDL-C and LDL-C; triglycerides); and fasting blood glucose as objective outcomes. We defined adverse events (e.g. gastrointestinal, nervous system, metabolism) and health-related quality of life as subjective outcomes.

Figure 2.

Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.

Figure 3.

Risk of bias summary: review authors' judgements about each risk of bias item for each included study.

Allocation

Four trials reported that allocation to groups was concealed (Joseph 1999; Kaats 1998; Kleefstra 2006; Yazaki 2010); the remainder did not explain how concealment was carried out, and were thus graded 'unclear' for the domain based on this criterion. Two trials provided details on random sequence generation (Joseph 1999; Kleefstra 2006).

Blinding

Five studies explicitly stated that blinding of participants and personnel was undertaken (Joseph 1999; Kaats 1996; Kaats 1998; Kleefstra 2006; Yazaki 2010). Four studies did not provide sufficient information about blinding procedures (Anton 2008; Campbell 1999; Iqbal 2009; Volpe 2001).

Incomplete outcome data

Numbers of study withdrawals were described in six studies that had losses to follow up (Anton 2008; Campbell 1999; Iqbal 2009; Kleefstra 2006; Volpe 2001; Yazaki 2010). Analysis was reported as ITT in one study (Iqbal 2009). No ITT analysis was undertaken in six trials (Anton 2008; Campbell 1999; Kaats 1996; Kleefstra 2006; Volpe 2001; Yazaki 2010). One study used PP analyses (Kleefstra 2006). Two studies did not report losses to follow up (Joseph 1999; Kaats 1998). Detailed descriptions of participants' withdrawals and reasons underpinning them were not provided in the study by Kaats 1996.

Selective reporting

All trials met a low 'Risk of bias' criteria for selective reporting, as they reported the prespecified primary outcomes and all expected outcomes.

Other potential sources of bias

Seven trials had a commercial source of funding possibly creating a risk of bias (Anton 2008; Campbell 1999; Iqbal 2009; Kaats 1996; Kaats 1998; Volpe 2001; Yazaki 2010).

Effects of interventions

See: Summary of findings for the main comparison

Baseline characteristics

For details of baseline characteristics, see Appendix 3 and Appendix 4.

Chromium picolinate (pooled doses versus placebo)

We focused this review on investigating which dose of CrP versus placebo would prove most effective and therefore specified the comparisons ranked according to CrP dose.

However, in order to find out whether CrP works in general, we also analysed the effect on body weight of the pooled CrP doses versus placebo. The MD in weight between CrP and placebo groups after 12 to 16 weeks of treatment was in favour of CrP (MD -1.1 kg (95% CI -1.7 to -0.4); P = 0.001; 392 participants; 6 trials; I2 = 0%; Analysis 1.1).

Chromium picolinate 200 μg versus placebo

Primary outcomes
Weight change outcomes

After 10 weeks of treatment, the one trial assessing weight loss (Kaats 1996) found no statistically significant differences in weight loss between the CrP 200 μg and placebo groups (MD -0.9 kg (95% CI -2.3 to 0.4); P = 0.18; 88 participants; Analysis 2.1). However, participants in the CrP groups lost a greater percentage of body fat (MD -1.1 kg (95% CI -2.0 to -0.2); P = 0.02; 88 participants; Analysis 2.2) and fat mass (MD -1.4 kg (95% CI -2.7 to -0.2); P = 0. 02; 88 participants; Analysis 2.3) than participants in the control groups.

Health-related quality of life

Not investigated.

Adverse events

Not reported.

Secondary outcomes
Death from any cause

Not reported.

Socioeconomic effects

Not investigated.

Chromium picolinate 400 μg versus placebo

Primary outcomes
Weight change outcomes
Change in body mass index

There was no statistically significant difference between the two groups at six weeks (MD 0.2 kg/m2 (95% CI -2.4 to 2.8); P = 0.88; 42 participants; 1 trial; Analysis 3.1.1) and 12 weeks (MD 1 kg/m2 (95% CI -1.3 to 3.3); P = 0.39; 42 participants; 1 trial; Analysis 3.1.2).

Change in weight loss

In a short-term, six-week trial there were no statistically significant differences between the two groups (MD -0.7 kg (95% CI -7.5 to 6.1); P = 0.84; 42 participants; 1 trial; Analysis 3.2.1). Three trials presented weight loss outcomes at around 12 weeks (Kaats 1996; Kaats 1998; Volpe 2001): participants in the CrP groups lost more weight than participants in the control intervention (MD -1.1 kg (95% CI -1.9 to -0.4); P = 0.003; 280 participants; 3 trials; I2 = 0%; Analysis 3.2.2).

Change in percentage body fat

No statistically significant differences were apparent at six weeks (MD -0.9% (95% CI -2 to 0.2); P = 0.12; 122 participants; 1 trial; Analysis 3.3.1) or at 12 weeks (MD -0.9% (95% CI -2 to 0.2); P = 0.10; 280 participants; 3 trials; I2 = 56%; Analysis 3.3.2).

Change in fat mass

No statistically significant differences were detected at six weeks (MD -0.4 kg (95% CI -4.6 to 3.8); P = 0.84; 42 participants; one trial; Analysis 3.4.1). At 12 weeks a decrease was observed in favour of CrP (MD -1.6 kg (95% CI -2.3 to -0.9); P < 0.0001; 280 participants; 3 trials; I2 = 0%; Analysis 3.4.2).

Change in waist circumference

The change in waist circumference was not statistically significantly different between the two groups at six weeks (MD 0.2 cm (95% CI -5.8 to 6.2); P = 0.95; 42 participants; 1 trial; Analysis 3.5.1) or 12 weeks (MD -1.4 cm (95% CI -7.7 to 4.9); P = 0.66; 37 participants; 1 trial; Analysis 3.5.2).

Health-related quality of life outcomes

Not investigated.

Adverse events

One participant receiving CrP and one participant receiving placebo experienced a serious adverse event (see Appendix 8). Two participants receiving placebo left the study due to adverse events (see Appendix 9).

Secondary outcomes
Change in fasting glucose

Fasting glucose was examined in a single study (Volpe 2001). There were no statistically significant differences between the CrP and placebo groups at 12 weeks (MD -2 mg/dL (95% CI -12 to 8); P = 0.70; 37 participants; 1 trial; Analysis 3.6).

Change in total cholesterol

There was no statistically significant difference between the CrP group and placebo group after 12 weeks of treatment (MD -0.5 mg/dL (95% CI -23 to 24); P = 0.97; 37 participants; 1 trial; Analysis 3.7) (Volpe 2001).

Change in triacylglycerol

Change in triacylglycerol levels was not statistically significantly different between the two groups at 12 weeks (MD 2 mg/dL (95% CI -39 to 43); P = 0.92; 37 participants; 1 trial; Analysis 3.8) (Volpe 2001).

Death from any cause

Not reported.

Socioeconomic effects

Not investigated.

Chromium picolinate 500 μg versus placebo

Two studies (Iqbal 2009; Kleefstra 2006) with a combined total of 91 participants included data on the effect of CrP 500 μg versus placebo.

Primary outcomes
Weight change outcomes
Change in body mass index

One study (Kleefstra 2006) found no statically significant differences between the CrP and placebo groups at six months (MD 0.2 kg/m2 (95% CI -0.45 to 0.9); P = 0.56; 31 participants; Analysis 4.1). Results were similar at 16 weeks (MD -0.8 kg/m2 (95% CI -2.2 to 0.5); P = 0.23; 62 participants; Analysis 4.2).

Change in waist circumference

The change in waist circumference at 16 weeks was not statistically significantly different between the two groups (MD 0.6 cm (95% CI -1 to 2.3); P = 0.45; 60 participants; 1 trial; Analysis 4.3).

Health-related quality of life outcomes

Not investigated.

Adverse events

Not reported.

Secondary outcomes
Change in fasting glucose

No statistically significant differences were detected at 16 weeks between groups (MD 0.4 mg/dL (95% CI -0.2 to 0.9); P = 0.17; 60 participants; 1 trial; Analysis 4.4).

Change in blood pressure

Change in blood pressure at 16 weeks was not statistically significantly different between the two groups, for either systolic blood pressure (MD 0 mm Hg (95% CI -12 to 12); P = 1.00; 31 participants; 1 trial; Analysis 4.5) or diastolic blood pressure (MD 2 mm Hg (95% CI -5 to 9); P = 0.56; 31 participants; 1 trial; Analysis 4.6).

Change in total cholesterol

Change in total cholesterol was reported in two studies (Iqbal 2009; Kleefstra 2006).There was no statistically significant difference between the intervention and placebo groups (MD -0.1 mg/dL (95% CI -0.5 to 0.4); P = 0.88; 91 participants; 1 trial; I2 = 0%; Analysis 4.7).

Change in triacylglycerol

There was no statistically significant difference between the CrP and placebo groups (MD -0.3 (95% CI -0.8 to 0.2); P = 0.26; 93 participants; 2 trials; I2 = 0%; Analysis 4.8).

Death from any cause

Not reported.

Socioeconomic effects

Not investigated.

Chromium picolinate 1000 μg versus placebo

Five studies (Anton 2008; Campbell 1999; Joseph 1999; Kleefstra 2006; Yazaki 2010) with a combined total of 207 participants included data on the effects of CrP 1000 μg versus placebo.

Primary outcomes
Weight change outcomes
Change in weight loss

After 12 weeks of treatment, two trials(Campbell 1999; Joseph 1999) found that there was no statistically significant difference in weight loss between groups (MD -0.7 kg (95% CI -7.3 to 5.9); P = 0.85; 50 participants; 2 trials; I2 = 0%; Analysis 5.1.1). Also, there was no statistically significant difference in BMI change at 24 weeks (MD 0.11 kg/m2 (95% CI -0.1 to 0.3); P = 0.25; 90 participants; 2 trials; Analysis 5.2.1) or 12 weeks (MD 0.3 kg/m2 (95% CI -0.01 to 0.6); P = 0.06; 99 participants; I2 = 0%; 2 trials; Analysis 5.2.2).

Change in percentage body fat

There was no statistically significant difference with regard to percentage body fat change between intervention and comparator groups at 24 weeks (MD 1% (95% CI -0.4 to 2.6); P = 0.14; 58 participants; 1 trial; Analysis 5.3.1) or 12 weeks (MD 0.9% (95% CI -0.4 to 2.2); P = 0.16; 117 participants; 3 trials; Analysis 5.3.2).

Change in waist circumference

The change in waist circumference at 12 weeks did not differ statistically significantly between the two groups (MD -1.6 cm (95% CI -6.5 to 3.3); P = 0.52; 32 participants; 1 trial; Analysis 5.4).

Health-related quality of life outcomes

Not investigated.

Adverse events

Two studies reported adverse events at six months and found no statistically significant differences between groups (RR 4.03 (95% CI 0.46 to 35.11); P = 0.21; 94 participants; I2 = 0%; Analysis 5.9.1); one study also found no statistically significant difference at 12 weeks (RR 0.30 (95% CI 0.01 to 7.02); P = 0.46; 40 participants; Analysis 5.9.2).

Two participants receiving CrP reported a serious adverse event (see Appendix 8) and left the study due to an adverse event (see Appendix 9).

Secondary outcomes
Change in fasting glucose

Fasting glucose was examined in two studies (Joseph 1999; Yazaki 2010) that found no statistically significant differences between groups at 12 weeks (MD 0.3 mg/dL (95% CI -1 to 1); P = 0.64; 99 participants; 2 trials; I2 = 43%; Analysis 5.5.1) or 6 months (MD 0 mg/dL (95% CI -2 to 2); P = 1.0; 58 participants; Analysis 5.5.2).

Change in total cholesterol

There was no statistically significant difference in total cholesterol between the two groups at 24 weeks (MD 0.1 mg/dL (95% CI -0.7 to 0.5); P = 0.81; 90 participants; 2 trials; I2 = 0%; Analysis 5.6.1) or 12 weeks (MD -0.1 mg/dL (95% CI -0.6 to 0.3); P = 0.57; 67 participants; 1 trial; Analysis 5.6.2).

Change in triacylglycerol

Change in triacylglycerol levels did not differ statistically significantly between the two groups at 6 months (MD -1 mg/dL (95% CI -3 to 1); P = 0.26; 90 participants; 2 trials; Analysis 5.7.1) or 12 weeks (MD -4 mg/dL (95% CI 95% CI -13 to 6); P = 0.45; 67 participants; 1 trial; Analysis 5.7.2).

Change in basal metabolic rate

Change in basal metabolic rate was not statistically significant between groups at 12 weeks (MD -0.4 MJ/day (95% CI 95% CI -1.4 to 0.6); P = 0.44; 18 participants; 1 trial; Analysis 5.8.1).

Change in blood pressure

Change in blood pressure did not differ statistically significantly between the two groups at 12 weeks (systolic blood pressure: MD 2 mm Hg (95% CI -1 to 5); P = 0.18; 67 participants; 1 trial; Analysis 5.10.1; diastolic blood pressure: MD 1 mm Hg (95% CI -2 to 4); P = 0.54; 67 participants; 1 trial; Analysis 5.11.1) or at 24 weeks (systolic blood pressure: MD 3 mm Hg (95% CI 95% -0.4 to 6); P = 0.08; 90 participants; 2 trials; I2 = 0%; Analysis 5.10.2; diastolic blood pressure: MD 3 mm Hg (95% CI -1 to 7); P = 0.13; 90 participants; 2 trials; I2 = 29%; Analysis 5.11.2).

Death from any cause

Not reported.

Socioeconomic effects

Not investigated.

Chromium picolinate 200 μg versus chromium picolinate 400 μg

One three-arm study (Kaats 1996) with a combined total of 99 participants investigated the effects of 200 µg CrP versus 400 µg CrP.

Primary outcomes
Weight change outcomes
Change in weight loss

After 10 weeks of treatment, there was no statistically significant difference between the two groups (MD 0.3 kg (95% CI -1 to 1.7); P = 0.65; 99 participants; Analysis 6.1).

Health-related quality of life outcomes

Not investigated.

Adverse events

Not reported.

Change in percentage body fat

No statistically significant difference between groups was apparent at 10 weeks (MD 0.5% (95% CI -0.5 to 1.5); P = 0.32; 99 participants; Analysis 6.2).

Change in fat mass

No statistically significant difference between groups was observed at 10 weeks (MD 0.5 kg (95% CI -0.7 to 1.6); P = 0.46; 99 participants; one trial; Analysis 6.3).

Secondary outcomes
Death from any cause

Not reported.

Socioeconomic effects

Not investigated

Chromium picolinate 500 μg versus chromium picolinate 1000 μg

One three-arm study (Kleefstra 2006) with 60 participants investigated the effects of 500 μg CrP versus 1000 μg CrP.

Primary outcomes
Weight change outcomes

After 24 weeks of treatment, one study found no statistically significant difference in change in BMI between groups (MD 0 kg/m2 (95% CI -0.8 to 0.8); P = 1.00; 29 participants; Analysis 7.1).

Health-related quality of life outcomes

Not investigated.

Adverse events

Adverse events did not differ significantly between groups at six months (RR 5.00 (95% CI 0.26 to 97); P = 0.29; 34 participants; Analysis 7.6).

Secondary outcomes
Change in total cholesterol

Total cholesterol change at 24 weeks showed no statistically significant difference between groups (MD -0.3 mg/dL (95% CI -0.8 to 0.2); P = 0.21; 29 participants; Analysis 7.2).

Change in triacylglycerol

Triacylglycerol levels showed no statistically significant difference between groups at 24 weeks (MD 0.1 mg/dL (95% CI -0.4 to 0.6); P = 0.71; 29 participants; Analysis 7.3).

Change in blood pressure

There was no statistically significant change in systolic blood pressure (MD -6 mm Hg (95% CI -19 to 7); P = 0.37; 29 participants; one trial; Analysis 7.4) or diastolic blood pressure (MD -4 mm Hg (95% CI -12 to 4); P = 0.33; 29 participants; Analysis 7.5) between groups at 24 weeks.

Death from any cause

Not reported.

Socioeconomic effects

Not investigated.

Subgroup analyses

As there was no statistical heterogeneity across the study results with regard to body weight, we did not analyse the data by subgroups.

Sensitivity analyses

We did not perform sensitivity analyses due to the low number of studies included.

Assessment of reporting bias

Not performed due to the low number of included trials.

Discussion

Summary of main results

Relatively few trials were identified that met the inclusion criteria for this review and most were relatively recent (published in the past 10 years). The trials were heterogeneous in nature, particularly in terms of interventions and outcomes, and sample sizes were small to medium, with 622 participants evaluated in total. The studies were conducted in the community setting, with interventions mainly delivered by health professionals, and provided outcome data at 12 to 16 weeks for weight and at 8 to 24 weeks for adverse events.

The findings of this review demonstrate that CrP supplements across all doses have some effect on weight loss after 12 to 16 weeks of treatment, but firm evidence for a specific dose could not be established.

Furthermore, there was no conclusive evidence for other outcomes of weight loss (e.g. BMI, waist circumference, percentage body fat), adverse events (e.g. gastrointestinal, nervous system, metabolism), blood pressure, lipids (e.g. total cholesterol, HDL-C, LDL-C, triglycerides) or fasting blood glucose.

Overall completeness and applicability of evidence

The duration of follow up of the included studies was a maximum of six months. Long-term efficacy was not evaluated, and only three trials (Anton 2008; Kleefstra 2006; Yazaki 2010) reported data on adverse events in each group. Therefore, the efficacy and safety of CrP could not firmly be established. Whether CrP supplementation should be used in clinical practice for overweight or obese people depends on the evaluation of its effects established by large double-blind RCTs investigating patient-important outcome measures.

Quality of the evidence

There was an unclear risk of selection bias for the majority of the included trials. Five studies explicitly stated that blinding of the participants and personnel was undertaken. Four studies did not provide sufficient information about blinding procedures. Numbers of study withdrawals were described in seven studies that had losses to follow-up. Analysis was reported as ITT in only one study. Two studies did not report losses to follow-up. No study could be clearly associated with selective reporting. Five trials had a commercial source of funding which may create a potential source of bias.

Potential biases in the review process

We used well-defined inclusion and exclusion criteria, independent data extraction by two assessors and the 'Risk of bias' assessment tool (Higgins 2009) in order to minimise potential biases in the review process. We conducted extensive electronic and manual searches to search for relevant articles. As we included only published data in our review, the possibility of publication bias cannot be ruled out. The major limitations of our review were that only a small number of studies met our inclusion criteria and a majority of these were of short-to-medium duration.

Agreements and disagreements with other studies or reviews

To date, one systematic review of 10 studies has been published that examined the effects of CrP in overweight or obese people (Pittler 2004). For body weight, a significant differential effect was found in favour of CrP (MD -1.1 kg (95% CI -1.8 to -0.4 kg); n = 489). This result is comparable to our pooled analysis of all CrP doses versus placebo. However, the clinical relevance of the effect is debatable. A definitive difference between our and Pittler's review is the fact that we included only participants who were overweight or obese at baseline.

Authors' conclusions

Implications for practice

We identified nine studies that met our inclusion criteria and most were relatively recent (published in the past 10 years). The trials were heterogeneous in nature, particularly in terms of interventions and outcomes, and sample sizes were small to medium, with 622 participants evaluated in total. The studies were conducted in the community setting, with interventions mainly delivered by health professionals, and were of short-to-medium follow up (six months or less). We found no current reliable evidence to inform firm decisions about the efficacy or safety of CrP supplements in overweight or obese adults.

Implications for research

An insufficient number of studies were included to enable us to examine the longer-term impact of CrP supplements in overweight or obese people. Only one study had a follow-up of six months. Further double-blind RCTs of CrP are required to provide more conclusive evidence. Trials evaluating patient-important outcomes, such as health-related quality of life and morbidity endpoints, should be large and of reasonable duration. In addition, future prospective studies that carefully investigate the underlying mechanisms of the potential effects of CrP in preventing people from becoming overweight or obese are encouraged.

Acknowledgements

The review authors would like to thank the following people for commenting on the review: Lun Li and Jinhui Tian who gave good advice for this review.

Data and analyses

Download statistical data

Comparison 1. Chromium (all dosages) versus placebo
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in weight at 12-16 weeks6392Mean Difference (IV, Random, 95% CI)-1.07 [-1.73, -0.42]
Analysis 1.1.

Comparison 1 Chromium (all dosages) versus placebo, Outcome 1 Change in weight at 12-16 weeks.

Comparison 2. Chromium (200 μg) versus placebo
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in weight at 10 weeks1 Mean Difference (IV, Random, 95% CI)Subtotals only
2 Change in percent body fat at 10 weeks [kg]1 Mean Difference (IV, Random, 95% CI)Subtotals only
3 Change in fat mass at 10 weeks [kg]1 Mean Difference (IV, Random, 95% CI)Subtotals only
Analysis 2.1.

Comparison 2 Chromium (200 μg) versus placebo, Outcome 1 Change in weight at 10 weeks.

Analysis 2.2.

Comparison 2 Chromium (200 μg) versus placebo, Outcome 2 Change in percent body fat at 10 weeks [kg].

Analysis 2.3.

Comparison 2 Chromium (200 μg) versus placebo, Outcome 3 Change in fat mass at 10 weeks [kg].

Comparison 3. Chromium (400 μg) versus placebo
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in body mass index1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
1.1 6 weeks1 Mean Difference (IV, Fixed, 95% CI)0.0 [0.0, 0.0]
1.2 12 weeks1 Mean Difference (IV, Fixed, 95% CI)0.0 [0.0, 0.0]
2 Change in weight3 Mean Difference (IV, Random, 95% CI)Subtotals only
2.1 6 weeks142Mean Difference (IV, Random, 95% CI)-0.7 [-7.51, 6.11]
2.2 12 weeks3280Mean Difference (IV, Random, 95% CI)-1.14 [-1.89, -0.39]
3 Percent body fat change3 Mean Difference (IV, Random, 95% CI)Subtotals only
3.1 Short-term1122Mean Difference (IV, Random, 95% CI)-0.87 [-1.95, 0.21]
3.2 Medium-term3280Mean Difference (IV, Random, 95% CI)-0.90 [-1.98, 0.18]
4 Change in fat mass3 Mean Difference (IV, Random, 95% CI)Subtotals only
4.1 6 weeks142Mean Difference (IV, Random, 95% CI)-0.43 [-4.61, 3.75]
4.2 12 weeks3280Mean Difference (IV, Random, 95% CI)-1.57 [-2.27, -0.87]
5 Change in waist circumference1 Mean Difference (IV, Fixed, 95% CI)Subtotals only
5.1 6 weeks142Mean Difference (IV, Fixed, 95% CI)0.20 [-5.81, 6.21]
5.2 12 weeks137Mean Difference (IV, Fixed, 95% CI)-1.40 [-7.72, 4.92]
6 Change in fasting glucose1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
6.1 12 weeks1 Mean Difference (IV, Fixed, 95% CI)0.0 [0.0, 0.0]
7 Change in total cholesterol1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
7.1 12 weeks1 Mean Difference (IV, Fixed, 95% CI)0.0 [0.0, 0.0]
8 Change in triacylglycerol1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
8.1 12 weeks1 Mean Difference (IV, Fixed, 95% CI)0.0 [0.0, 0.0]
Analysis 3.1.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 1 Change in body mass index.

Analysis 3.2.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 2 Change in weight.

Analysis 3.3.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 3 Percent body fat change.

Analysis 3.4.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 4 Change in fat mass.

Analysis 3.5.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 5 Change in waist circumference.

Analysis 3.6.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 6 Change in fasting glucose.

Analysis 3.7.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 7 Change in total cholesterol.

Analysis 3.8.

Comparison 3 Chromium (400 μg) versus placebo, Outcome 8 Change in triacylglycerol.

Comparison 4. Chromium (500 μg) versus placebo
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in body mass index at 6 months1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
2 Change in weight at 16 weeks1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
3 Change in waist circumference at 16 weeks1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
4 Change in fasting glucose at 16 weeks1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
5 Change in systolic blood pressure at 6 months1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
6 Change in diastolic blood pressure at 6 months1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
7 Change in total cholesterol291Mean Difference (IV, Random, 95% CI)-0.05 [-0.46, 0.37]
8 Change in triacylglycerol293Mean Difference (IV, Random, 95% CI)-0.28 [-0.76, 0.21]
Analysis 4.1.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 1 Change in body mass index at 6 months.

Analysis 4.2.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 2 Change in weight at 16 weeks.

Analysis 4.3.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 3 Change in waist circumference at 16 weeks.

Analysis 4.4.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 4 Change in fasting glucose at 16 weeks.

Analysis 4.5.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 5 Change in systolic blood pressure at 6 months.

Analysis 4.6.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 6 Change in diastolic blood pressure at 6 months.

Analysis 4.7.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 7 Change in total cholesterol.

Analysis 4.8.

Comparison 4 Chromium (500 μg) versus placebo, Outcome 8 Change in triacylglycerol.

Comparison 5. Chromium (1000 μg) versus placebo
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in weight2 Mean Difference (IV, Fixed, 95% CI)Subtotals only
1.1 12 weeks250Mean Difference (IV, Fixed, 95% CI)-0.66 [-7.25, 5.93]
2 Change in body mass index3 Mean Difference (IV, Random, 95% CI)Subtotals only
2.1 6 months290Mean Difference (IV, Random, 95% CI)0.11 [-0.08, 0.30]
2.2 12 weeks299Mean Difference (IV, Random, 95% CI)0.28 [-0.01, 0.58]
3 Change in percent body fat3 Mean Difference (IV, Random, 95% CI)Subtotals only
3.1 6 months158Mean Difference (IV, Random, 95% CI)1.1 [-0.35, 2.55]
3.2 12 weeks3117Mean Difference (IV, Random, 95% CI)0.93 [-0.35, 2.21]
4 Change in waist circumference1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
4.1 12 weeks1 Mean Difference (IV, Fixed, 95% CI)-1.60 [-6.53, 3.33]
5 Change in fasting glucose2 Mean Difference (IV, Random, 95% CI)Subtotals only
5.1 12 weeks299Mean Difference (IV, Random, 95% CI)-0.25 [-1.29, 0.80]
5.2 6 months158Mean Difference (IV, Random, 95% CI)0.0 [-2.14, 2.14]
6 Change in total cholesterol2 Mean Difference (IV, Random, 95% CI)Subtotals only
6.1 6 months290Mean Difference (IV, Random, 95% CI)-0.07 [-0.68, 0.53]
6.2 12 weeks167Mean Difference (IV, Random, 95% CI)-1.80 [-8.03, 4.43]
7 Change in triacylglycerol2 Mean Difference (IV, Random, 95% CI)Subtotals only
7.1 6 months290Mean Difference (IV, Random, 95% CI)-1.16 [-3.19, 0.87]
7.2 12 weeks167Mean Difference (IV, Random, 95% CI)-3.7 [-13.38, 5.98]
8 Change in basal metabolic rate1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
8.1 12 weeks1 Mean Difference (IV, Fixed, 95% CI)0.0 [0.0, 0.0]
9 Adverse events3134Risk Ratio (M-H, Random, 95% CI)1.75 [0.30, 10.43]
9.1 6 months294Risk Ratio (M-H, Random, 95% CI)4.03 [0.46, 35.11]
9.2 12 weeks140Risk Ratio (M-H, Random, 95% CI)0.30 [0.01, 7.02]
10 Change in systolic blood pressure2 Mean Difference (IV, Fixed, 95% CI)Subtotals only
10.1 12 weeks167Mean Difference (IV, Fixed, 95% CI)2.1 [-0.95, 5.15]
10.2 6 months290Mean Difference (IV, Fixed, 95% CI)2.88 [-0.36, 6.12]
11 Change in diastolic blood pressure2 Mean Difference (IV, Random, 95% CI)Subtotals only
11.1 12 weeks167Mean Difference (IV, Random, 95% CI)0.9 [-2.01, 3.81]
11.2 6 months290Mean Difference (IV, Random, 95% CI)2.83 [-0.88, 6.55]
Analysis 5.1.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 1 Change in weight.

Analysis 5.2.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 2 Change in body mass index.

Analysis 5.3.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 3 Change in percent body fat.

Analysis 5.4.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 4 Change in waist circumference.

Analysis 5.5.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 5 Change in fasting glucose.

Analysis 5.6.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 6 Change in total cholesterol.

Analysis 5.7.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 7 Change in triacylglycerol.

Analysis 5.8.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 8 Change in basal metabolic rate.

Analysis 5.9.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 9 Adverse events.

Analysis 5.10.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 10 Change in systolic blood pressure.

Analysis 5.11.

Comparison 5 Chromium (1000 μg) versus placebo, Outcome 11 Change in diastolic blood pressure.

Comparison 6. Chromium (200 μg) versus chromium (400 μg)
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in weight 10 weeks1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
2 Change in percent body fat 10 weeks1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
3 Change in fat mass 10 weeks1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
Analysis 6.1.

Comparison 6 Chromium (200 μg) versus chromium (400 μg), Outcome 1 Change in weight 10 weeks.

Analysis 6.2.

Comparison 6 Chromium (200 μg) versus chromium (400 μg), Outcome 2 Change in percent body fat 10 weeks.

Analysis 6.3.

Comparison 6 Chromium (200 μg) versus chromium (400 μg), Outcome 3 Change in fat mass 10 weeks.

Comparison 7. Chromium (500 μg) versus chromium (1000 μg) at 6 months
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 Change in body mass index1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
2 Change in total cholesterol1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
3 Change in triacylglycerol1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
4 Change in systolic blood pressure1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
5 Change in diastolic blood pressure1 Mean Difference (IV, Fixed, 95% CI)Totals not selected
6 Adverse effects1 Risk Ratio (M-H, Random, 95% CI)Totals not selected
Analysis 7.1.

Comparison 7 Chromium (500 μg) versus chromium (1000 μg) at 6 months, Outcome 1 Change in body mass index.

Analysis 7.2.

Comparison 7 Chromium (500 μg) versus chromium (1000 μg) at 6 months, Outcome 2 Change in total cholesterol.

Analysis 7.3.

Comparison 7 Chromium (500 μg) versus chromium (1000 μg) at 6 months, Outcome 3 Change in triacylglycerol.

Analysis 7.4.

Comparison 7 Chromium (500 μg) versus chromium (1000 μg) at 6 months, Outcome 4 Change in systolic blood pressure.

Analysis 7.5.

Comparison 7 Chromium (500 μg) versus chromium (1000 μg) at 6 months, Outcome 5 Change in diastolic blood pressure.

Analysis 7.6.

Comparison 7 Chromium (500 μg) versus chromium (1000 μg) at 6 months, Outcome 6 Adverse effects.

Appendices

Appendix 1. Search strategies

Search terms and databases

Unless otherwise stated, search terms are free text terms.

Abbreviations:

'$': stands for any character; '?': substitutes one or no character; adj: adjacent (i.e. number of words within range of search term); exp: exploded MeSH; MeSH: medical subject heading (MEDLINE medical index term); pt: publication type; sh: MeSH; tw: text word.

The Cochrane Library
#1 MeSH descriptor Obesity explode all trees
#2 MeSH descriptor Weight Gain explode all trees
#3 MeSH descriptor Weight Loss explode all trees
#4 MeSH descriptor Body Mass Index explode all trees
#5 (overweight in All Text or (over in All Text and weight in All Text) )
#6 (adipos* in All Text or (fat in All Text and overload in All Text and syndrom* in All Text))
#7 (overeat* in All Text or (over in All Text and eat* in All Text) )
#8 (overfeed* in All Text or (over in All Text and feed* in All Text) )
#9 (weight in All Text and (gain in All Text or chang* in All Text) )
#10 (body in All Text and mass in All Text and ind* in All Text)
#11 MeSH descriptor Waist circumference explode all trees
#12 MeSH descriptor Waist-Hip Ratio explode all trees
#13 MeSH descriptor Abdominal fat explode all trees
#14 MeSH descriptor Body fat distribution explode all trees
#15 MeSH descriptor Skinfold thickness explode all trees
#16 MeSH descriptor Overweight explode all trees
#17 ((weight in All Text near/6 cyc* in All Text) or (weight in All Text near/6 reduc* in All Text) or (weight in All Text near/6 los* in All Text) or (weight in All Text near/6 maint* in All Text) or (weight in All Text near/6 decreas* in All Text) )
#18 ((weight in All Text near/6 watch* in All Text) or (weight in All Text near/6 control* in All Text) or (weight in All Text near/6 chang* in All Text) or (weight in All Text near/6 gain* in All Text))
#19 BMI in All Text
#20 (waist-hip in All Text and ratio* in All Text)
#21 (waist in All Text and circumferenc* in All Text)
#22 (body in All Text and (fat in All Text near/6 distribution* in All Text) )
#23 ((abominal in All Text and fat in All Text) or (skinfold in All Text and thickness in All Text))
#24 (obes* in All Text or adipos* in All Text)
#25 (#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8 or #9 or #10 or #11 or #12)
#26 (#13 or #14 or #15 or #16 or #17 or #18 or #19 or #20 or #21 or #22 or #23 or #24)
#27 (#25 or #26)
#28 MeSH descriptor chromium picolinate explode all trees
#29 chromium picolinate in All Text
#30 (#28 or #29)
#31(#27 and #30)
MEDLINE

1 exp Obesity/ or exp Obesity hypoventilation syndrome/ or exp Obesity, abdominal/ or exp Obesity, morbid/ or exp Prader-Willi Syndrome/ 

2 exp Overweight/ 

3 exp Adipose tissue/ 

4 exp Weight gain/ or exp Weight loss/ 

5 exp body fat distribution/ or exp body mass index/ or exp waist circumference/ or exp skinfold thickness/ or exp waist-hip ratio/ 

6 exp Body Composition/ 

7 (overweight$ or over weight$).tw,ot. 

8 fat overload syndrom$.tw,ot. 

9 (overeat$ or over eat$).tw,ot. 

10 (overfeed$ or over feed$).tw,ot. 

11 (adipos$ or obes$).tw,ot. 

12 (weight adj3 (cyc$ or reduc$ or los$ or maint$ or decreas$ or watch$ or control$ or gain$ or chang$)).tw,ot. 

13 (body mass ind$ or waist-hip ratio$).tw,ot. 

14 skinfold thickness$.tw,ot. 

15 abdominal fat$.tw,ot. 

16 ((abdominal or subcutaneous or intra-abdominal or visceral or retroperitoneal or retro peritoneal) adj3 fat*).tw,ot. 

17 or/1-16 

18 exp chromium picolinate/ 

19 chromium picolinate.tw,ot. 

20 18 or 19 

21 17 and 20 

22 randomized controlled trial.pt. 

23 controlled clinical trial.pt. 

24 randomi?ed.ab. 

25 placebo.ab. 

26 drug therapy.fs. 

27 randomly.ab. 

28 trial.ab. 

29 groups.ab. 

30 or/22-29 

31 Meta-analysis.pt. 

32 exp Technology Assessment, Biomedical/ 

33 exp Meta-analysis/ 

34 exp Meta-analysis as topic/ 

35 hta.tw,ot. 

36 (health technology adj6 assessment$).tw,ot. 

37 (meta analy$ or metaanaly$ or meta?analy$).tw,ot. 

38 (search* adj10 (medical databas*or medline or pubmed or embase or cochrane or cinahl or psycinfo or psyclit or healthstar or biosis or current content* or systemat*)).tw,ot. 

39 or/31-38 

40 30 or 39 

41 (comment or editorial or historical-article).pt. 

42 40 not 41 

43 21 and 42 

44 (animals not (animals and humans)).sh. 

45 43 not 44 

EMBASE

1 exp Obesity/ 

2 exp weight change/ or exp weight control/ or exp weight gain/ or exp weight reduction/ 

3 exp body mass/ or exp waist circumference/ or exp waist hip ratio/ 

4 exp abdominal fat/ or exp body fat distribution/ 

5 exp skinfold thickness/ 

6 (obes$ or adipos* or overweight or over weight).tw,ot. 

7 (overeat or over eat or overfeed or over feed or fat overload syndrom$).tw,ot. 

8 (weight adj6 (cyc$ or reduc$ or los$ or maint$ or decreas$ or watch$ or control or chang$ or gain)).tw,ot. 

9 (body mass ind$ or waist hip ratio or waist circumferenc$).tw,ot. 

10 (body fat adj3 distribution*).tw,ot. 

11 (abdominal fat or skinfold thickness).tw,ot. 

12 or/1-11 

13 exp chromium picolinate/ 

14 chromium picolinate.tw,ot. 

15 13 or 14 

16 12 and 15 

17 exp Randomized Controlled Trial/ 

18 exp Controlled Clinical Trial/ 

19 exp Clinical Trial/ 

20 exp Comparative Study/ 

21 exp Drug comparison/ 

22 exp Randomization/ 

23 exp Crossover procedure/ 

24 exp Double blind procedure/ 

25 exp Single blind procedure/ 

26 exp Placebo/ 

27 exp Prospective Study/ 

28 ((clinical or control$ or comparativ$ or placebo$ or prospectiv$ or randomi?ed) adj3 (trial$ or stud$)).ab,ti. 

29 (random$ adj6 (allocat$ or assign$ or basis or order$)).ab,ti. 

30 ((singl$ or doubl$ or trebl$ or tripl$) adj6 (blind$ or mask$)).ab,ti. 

31 (cross over or crossover).ab,ti. 

32 or/17-31 

33 exp meta analysis/ 

34 (metaanaly$ or meta analy$ or meta?analy$).ab,ti,ot. 

35 (search$ adj10 (medical database$ or medline or pubmed or embase or cochrane or cinahl or psycinfo or psyclit or healthstar or biosis or current content$ or systematic$)).ab,ti,ot. 

36 exp Literature/ 

37 exp Biomedical Technology Assessment/ 

38 hta.tw,ot. 

39 (health technology adj6 assessment$).tw,ot. 

40 or/33-39 

41 32 or 40 

42 (comment or editorial or historical-article).pt. 

43 41 not 42 

44 16 and 43 

45 limit 44 to human 

46 44 not 45 

ISI Web of Knowledge

#1 Topic= (Obesity) OR Topic= (Overweight) OR Topic= (Weight Gain) OR Topic= (Weight Loss) OR Topic= (Body Mass Index) OR Topic= (Waist circumference) OR Topic= (Waist-Hip Ratio) OR Topic= (Abdominal fat) OR Topic= (Body fat distribution) OR Topic= (Skinfold thickness) OR Topic= (BMI) 

#2 Topic= (chromium picolinate) 

#3 #1 AND #2 (201 citations)

Chinese Biomedical Database (CBM)

#1 "Obesity"[Mesh] 

#2 Obesity [ti/ab] 

#3 "Overweight"[Mesh]

#4 "Overweight"[ti/ab]  

#5 Weight Gain [ti/ab] 

#6 "Weight Gain"[Mesh]

#7 Weight Loss [ti/ab] 

#8 "Weight Loss"[Mesh]
#9 Body Mass Index [ti/ab] 

#10 "Body Mass Index"[Mesh]

#11 Waist circumference [ti/ab] 

#12"Waist circumference"[Mesh] 

#13 Waist-Hip Ratio [ti/ab] 

#14"Waist-Hip Ratio"[Mesh] 

#15 "Abdominal fat"[ti/ab] 

#16"Abdominal fat"[Mesh] 

#17 Body fat distribution [ti/ab] 

#18 "Body fat distribution"[Mesh] 

#19 Skinfold thickness [ti/ab] 

#20 Skinfold thickness [Mesh] 

#21 "BMI"[Mesh] 

#22 BMI [ti/ab] 

#23 #1 OR #2 OR #3 OR #4 OR #5 OR #6 OR #7 OR #8 OR #9 OR #10 OR #11 OR #12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19 OR #20 OR #21 OR #22 

#24 chromium picolinate[ti/ab] 

#25 "chromium picolinate"[Mesh] 

#26 #24 OR #25 

#27 #23 AND #26 

#28 limit 27 to human 

China Journal Full-text Database

#1 Obesity OR Overweight OR Weight Gain OR Weight Loss OR Body Mass Index OR Waist circumference OR Waist-Hip Ratio OR Abdominal fat OR Body fat distribution OR Skinfold thickness OR BMI 

#2 chromium picolinate

#3 #1 AND #2 

Chinese Scientific Journals Full-text Database

#1 Obesity OR Overweight OR Weight Gain OR Weight Loss OR Body Mass Index OR Waist circumference OR Waist-Hip Ratio OR Abdominal fat OR Body fat distribution OR Skinfold thickness OR BMI 

#2 chromium picolinate

#3 #1 AND #2 

'My NCBI' alert service
("picolinic acid" [Supplementary Concept] OR "picolinic acid" [All Fields] OR "chromium picolinate" [All Fields]) AND Randomized Controlled Trial [ptyp]

Appendix 2. Description of interventions

CharacteristicIntervention(s) [route, frequency, total dose/day]Comparator(s) [route, frequency, total dose/day]
Kaats 1996I1: chromium picolinate once a day, 200 μg/dayPlacebo once a day
I2: chromium picolinate once a day, 400 μg/day
Kaats 1998 Chromium picolinate once a day, 400 μg/dayPlacebo once day
Joseph 1999Chromium picolinate twice daily, 1000 μg/day + RT (twice weekly for 12 weeks)Placebo + RT (twice weekly for 12 weeks)
Kleefstra 2006I1: Chromium picolinate twice daily, 500 μg/dayPlacebo capsule twice daily
I2: Chromium picolinate twice daily, 1000 μg/day
Iqbal 2009Chromium picolinate capsule twice daily, 500 μg/dayPlacebo capsule twice daily
Volpe 2001Chromium picolinate once a day, 400 μg/day + a supervised weight-training and walking program (twice weekly for 12 weeks)Placebo once a day + a supervised weight-training and walking program (twice weekly for 12 weeks)
Anton 2008Chromium picolinate 1000 μg/dayPlacebo
Campbell 1999Chromium picolinate twice daily, 924 μg/day + RT (twice weekly for 12 weeks)Placebo twice daily + RT (twice weekly for 12 weeks)
Yazaki 2010Chromium picolinate capsule twice daily, 500 μgPlacebo capsule twice daily, 815 mg

Footnotes

I: intervention; RT: resistance training

Appendix 3. Baseline characteristics (I)

CharacteristicIntervention(s) and comparator(s)Duration of
intervention
Participating populationStudy period
[year(s)]
CountrySettingDuration of disease
[mean/range years
(SD), or as reported]
Kaats 1996I1: CrP 200 μg/day72 daysParticipants were recruited from the first 233 volunteers who responded to a news story about the study run on the local central broad-casting system1996USACommunity volunteer-
I2: CrP 400 μg/day
C: placebo
Kaats 1998I: CrP 400 μg/day90 daysParticipants were recruited from a variety of fitness and athletic clubs in San Antonio and Houston, Texas1998USACommunity volunteer-
C: placebo
Joseph 1999I: CrP 1000 μg/day + resistance training12 weeksModerately overweight older men and women1999USACommunity volunteer-
C: placebo + resistance training
Kleefstra 2006I1: CrP 500 μg/day6 monthsParticipants with type 2 diabetes mellitus2006USAOutpatients-
I2: CrP 1000 μg/day
C: placebo
Iqbal 2009I: CrP 500 μg/day16 weeksNondiabetic participants aged 18 to 75 years with metabolic syndrome and abdominal adiposity2009USAOutpatients-
C: placebo
Volpe 2001I: CrP 400 μg/day + weight training12 weeksPre-menopausal women with a BMI between 27 and 41 kg/m22001USACommunity volunteer-
C: placebo + weight training
Anton 2008I: CrP 400 μg/day8 weeksHealthy, overweight adult women who reported craving for carbohydrates2008USACommunity volunteer-
C: placebo
Campbell 1999I: CrP 1000 μg/day + resistance training13 weeksOlder men1999USACommunity volunteer-
C: placebo + resistance training
Yazaki 2010I: CrP 400 μg/day24 weeksHealthy overweight adults2010USACommunity volunteer-
C: placebo

Footnotes

"-" denotes not reported

BMI: body mass index; C: comparator: CrP: chromium picolinate; I: intervention; SD: standard deviation

Appendix 4. Baseline characteristics (II)

CharacteristicIntervention(s) and comparator(s)Sex
[female %]
Age
[mean/range years (SD),
or as reported]
FBG
[mg/dl]
BP systolic/diastolic
[mm Hg]
BMI
[mean kg/m2]
Co-medications /
Co-interventions
Co-morbidities
Kaats 1996I1: CrP 200 μg/day-45.9 ± 11.9--30.3 ± 5.5--
I2: CrP 400 μg/day-45.7 ± 11.8--30.6 ± 5.1--
C: placebo-44.3 ± 11.2--30.6 ± 5.5--
Kaats 1998 I: CrP 400 μg/day-41.1 ± 10.5--30.2 ± 7.1--
C: placebo-43.5 ± 7.6--28.4 ± 5.4--
Joseph 1999I: CrP 1000 μg/day + resistance training47.163 ± 45.73 ± 0.43 mmol/L-28.9 ± 2.5Control diet + resistance training-
C: placebo + resistance training46.760 ± 45.73 ± 0.43 mmol/L-29.3 ± 2.4Control diet + resistance training-
Kleefstra 2006I1: CrP 500 μg/day86.260 ± 8.8-147 ± 24 / 85 ± 1035 ± 7.2Insulin-
I2: CrP 1000 μg/day84.959 ± 6.4-156 ± 25 / 84 ± 1433 ± 4.2Insulin-
C: placebo83.162 ± 7.5-159 ± 20 / 83 ± 1034 ± 4.3Insulin-
Iqbal 2009I: CrP 500 μg/day60.647.7 ± 104.74 ± 0.8 mmol/L130 ± 12 / 81 ± 1037.8 ± 9Insulin-
C: placebo30.051.1 ± 134.54 ± 0.6 mmol/L129 ± 15 / 79 ± 1035.2 ± 6Insulin-
Volpe 2001I: CrP 400 μg/day + weight training10042.6 ± 6.542.6 ± 6.591 ± 1327-41Weight training-
C: placebo + weight training10042.5 ± 4.242.5 ± 4.291 ± 627-41Weight training-
Anton 2008I: CrP 400 μg/day032 ± 10.287.1 ± 1.4115 ± 13 / 74 ± 1030.7 ± 4.2Control diet-
C: placebo034.5 ± 9.787.9 ± 6.8114 ± 11 / 74 ± 1031.9 ± 4.7Control diet-
Campbell 1999I: CrP 1000 μg/day + resistance training050-75--27-34Resistance training-
C: placebo + resistance training050-75--27-34Resistance training-
Yazaki 2010I: CrP 400 μg/day5025-75-133 ± 17 / 80 ± 1036.0 ± 6.7--
C: placebo5025-75-137 ± 18 / 81 ± 1136.1 ± 7.6--

Footnotes

"-" denotes not reported

"±" denotes single standard deviation

BP: blood pressure; BMI: body mass index; C: control; CrP: chromium picolinate; FBG: fasting blood glucose; I: intervention

Appendix 5. Matrix of study endpoints (publications)

Characteristic

Study ID

EndpointTime of measurementaOutcome reportingb
[analysed & reported
as not significant (e.g. P > 0.05)]
Outcome reportingb
[analysed but not reported]
Outcome reportingb
[measured & not analysed or analysed but not reported because of non-significant results ]
Outcome reportingb
[not mentioned but likely to have been measured & analysed but not reported because of non-significant results]
Kaats 1996 Body composition improvement (P) 0, 72 daysN/AN/AN/AN/A
Body weight (P) 0, 72 daysxN/AN/AN/A
Fat weight (P) 0, 72 daysN/AN/AN/AN/A
Percentage body fat (S) 0, 72 daysN/AN/AN/AN/A
Non-fat mass (S) 0, 72 daysxN/AN/AN/A
Kaats 1998   Body weight (P) 0, 90 daysN/AN/AN/AN/A
Fat weight (P) 0, 90 daysN/AN/AN/AN/A
Percentage body fat (S) 0, 90 daysN/AN/AN/AN/A
Fat-free mass (S) 0, 90 daysxN/AN/AN/A
Joseph 1999Fasting glucose (P) 1, 13 weeksN/AN/AN/AN/A
Fasting insulin (P) 1, 13 weeksxN/AN/AN/A
Fasting C-peptide (S) 1, 13 weeksxN/AN/AN/A
Weight loss (S) 1, 13 weeksN/AN/AN/AN/A
BMI (S) 1, 13 weeksxN/AN/AN/A
Waist circumference (S) 1, 13 weeksxN/AN/AN/A
Waist to hip ratio (O) 1, 13 weeksxN/AN/AN/A
Kleefstra 2006A1c (P) 0, 1, 3, 6 monthsxN/AN/AN/A
Lipid profile (S) 0, 1, 3, 6 monthsxN/AN/AN/A
BMI (S) 0, 1, 3, 6 monthsxN/AN/AN/A
Blood pressure (S) 0, 1, 3, 6 monthsxN/AN/AN/A
Plasma chromium concentration (S) 0, 1, 3, 6 monthsxN/AN/AN/A
Iqbal 2009Insulin sensitivity index (P) 0, 16 weeksxN/AN/AN/A
Glucose metabolism (S) 0, 16 weeksN/AN/AN/AN/A
Oxidative stress (S) 0, 16 weeksxN/AN/AN/A
Fasting serum lipids (S) 0, 16 weeksxN/AN/AN/A
C-reactive protein (S) 0, 16 weeksxN/AN/AN/A
Weight (O) 0, 16 weeksxN/AN/AN/A
Waist circumference (O) 0, 16 weeksxN/AN/AN/A
Volpe 2001 Percentage body fat (P) 0, 6, 12 weeksN/AN/AN/AN/A
Fat mass (P) 0, 6, 12 weeksN/AN/AN/AN/A
BMI (P) 0, 6, 12 weeksxN/AN/AN/A
Body weight (P) 0, 6, 12 weeksxN/AN/AN/A
Resting metabolic rate (P) 0, 6, 12 weeksxN/AN/AN/A
Biochemical parameters (S) 0, 6, 12 weeksxN/AN/AN/A
Anton 2008Food intake (P) 0, 1, 8 weeksN/AN/AN/AN/A
Hunger levels (P) 0, 1, 8 weeksN/AN/AN/AN/A
Adverse events (P) 0, 1, 8 weeksN/AN/AN/AN/A
Body weight (S) 0, 1, 8 weeksN/AN/AN/AN/A
Fat cravings (S) 0, 1, 8 weeksN/AN/AN/AN/A
Glucose and insulin (O) 0, 1, 8 weeksxN/AN/AN/A
Campbell 1999 Fat-free mass (P) 0, 6, 12 weeksN/AN/AN/AN/A
Body weight (P) 0, 6, 12 weeksxN/AN/AN/A
Urinary creatinine excretion (P) 0, 6, 12 weeksN/AN/AN/AN/A
Total body water (P) 0, 6, 12 weeksN/AN/AN/AN/A
Body muscle mass (P) 0, 6, 12 weeksN/AN/AN/AN/A
Vastus lateralis type II fibre area (S) 0, 6, 12 weeksN/AN/AN/AN/A
Skinfold thickness (S) 0, 6, 12 weeksN/AN/AN/AN/A
Resting metabolic rate (S) 0, 6, 12 weeksxN/AN/AN/A
Percentage body fat (S) 0, 6, 12 weeksN/AN/AN/AN/A
Fat mass (S) 0, 6, 12 weeksN/AN/AN/AN/A
Yazaki 2010 BMI (P) 0, 12, 24 weeksxN/AN/AN/A
Waist to hip ratio (P) 0, 12, 24 weeksxN/AN/AN/A
Percentage body fat (S) 0, 12, 24 weeksxN/AN/AN/A
Blood pressure (S) 0, 12, 24 weeksxN/AN/AN/A
Basic metabolic (S) 0, 12, 24 weeksxN/AN/AN/A
Urinalysis (O) 0, 12, 24 weeksxN/AN/AN/A

Footnotes:

"-" denotes not reported

"x" denotes "yes"

aUnderlined times of measurement denote data as reported in the results section of the publication (other times represent planned but not reported points in time)

bConstitutes 'high risk of bias' according to the Outcome Reporting Bias In Trials (ORBIT) study classification system for missing or incomplete outcome reporting in reports of randomised trials (Kirkham 2010)

(P) primary or (S) secondary endpoint(s) refer to verbatim statements in the publication, (O) other endpoints relate to outcomes which were not specified as 'primary' or 'secondary' outcomes in the publication

Endpoint in bold = review primary outcome

A1c: HbA1c (glycosylated haemoglobin A1c); BMI: body mass index; N/A: not applicable

Appendix 6. Matrix of study endpoints (protocol/trial documents)

Characteristic

Study ID (trial identifier)

EndpointTime of measurement
Kaats 1996--
Kaats 1998 --
Joseph 1999--
Kleefstra 2006--
Iqbal 2009

Insulin sensitivity index, glucose metabolism, oxidative stress,

fasting serum lipids, C-reactive protein, weight, waist circumference

0, 16 weeks
Volpe 2001--
Anton 2008--
Campbell 1999--
Yazaki 2010--

Footnotes

"-" denotes no protocol was detected

Appendix 7. Definition of endpoint measurement

Characteristic

Study ID

Overweight and obesityCardiovascular mortalityMorbidityHealth-related quality of life
Kaats 1996WHO guidelines---
Kaats 1998 WHO guidelines---
Joseph 1999WHO guidelines---
Kleefstra 2006WHO guidelines---
Iqbal 2009WHO guidelines---
Volpe 2001WHO guidelines---
Anton 2008WHO guidelines---
Campbell 1999WHO guidelines---
Yazaki 2010WHO guidelines---

Footnotes

"-" denotes not reported

WHO: World Health Organization

Appendix 8. Adverse events (I)

Characteristic

Study ID

Intervention(s) and comparator(s)Randomised /
Safety [N]
Deaths [N]All adverse
events
[N]
All adverse
events
[%]
Severe/serious
adverse events
[N]
Severe/serious
adverse events
[%]
Kaats 1996I1: CrP 200 μg/day33No participant died----
I2: CrP 400 μg/day66No participant died----
C: placebo55No participant died----
Kaats 1998I: CrP 400 μg/day62No participant died----
C: placebo60No participant died----
Joseph 1999I: CrP 1000 μg/day + resistance training17No participant died----
C: placebo + resistance training15No participant died----
Kleefstra 2006I1: CrP 500 μg/day17No participant died0000
I2: CrP 1000 μg/day17/15No participant died213213
C: placebo19No participant died0000
Iqbal 2009I: CrP 500 μg/day33No participant died----
C: placebo30No participant died----
Volpe 2001I: CrP 400 μg/day + weight training22No participant died----
C: placebo + weight training20No participant died----
Anton 2008I: CrP 400 μg/day21No participant died0000
C: placebo19/18No participant died1616
Campbell 1999I: CrP 1000 μg/day + resistance training9No participant died----
C: placebo + resistance training9No participant died----
Yazaki 2010I: CrP 400 μg/day40/39No participant died1313
C: placebo40No participant died0000

Footnotes

"-" denotes not reported

C: control; CrP: chromium picolinate; I: intervention

Appendix 9. Adverse events (II)

CharacteristicIntervention(s) and comparator(s)Randomised /
Safety [N]
Left study
due
to adverse
events
[N]
Left study
due
to adverse
events
[%]
Hospitalisation
[N]
Hospitalisation
[%]
Outpatient
treatment
[N]
Outpatient
treatment
[%]
Symptoms
[N]
Symptoms
[%]
Kaats 1996I1: CrP 200 μg/day33--------
I2: CrP 400 μg/day66--------
C: placebo55--------
Kaats 1998I: CrP 400 μg/day62--------
C: placebo60--------
Joseph 1999I: CrP 1000 μg/day + resistance training17--------
C: placebo + resistance training15--------
Kleefstra 2006I1: CrP 500 μg/day1700------
I2: CrP 1000 μg/day17/15213------
C: placebo1900------
Iqbal 2009I: CrP 500 μg/day33--------
C: placebo30--------
Volpe 2001I: CrP 400 μg/day + weight training22--------
C: placebo + weight training20--------
Anton 2008I: CrP 400 μg/day2100000000
C: placebo19/1816------
Campbell 1999I: CrP 1000 μg/day + resistance training9--------
C: placebo + resistance training9--------
Yazaki 2010I: CrP 400 μg/day40/3900000000
C: placebo4016------

Footnotes

"-" denotes not reported

C: control; CrP: chromium picolinate; I: intervention

Appendix 10. Survey of authors' providing information on trials

We tried our best to obtain relevant missing data from all authors of included studies but received no reply.

Contributions of authors

Hongliang Tian (TH): protocol drafting, search strategy development, trial selection, data interpretation and review drafting.

Xiaohu Guo (GX): protocol drafting, trial selection, data extraction, data analysis, data interpretation and review drafting.

Xiyu Wang (WX): protocol drafting, search strategy development, acquiring trial reports and review drafting.

Zhiyun He (HZ): acquiring trial reports, trial selection, data extraction, data analysis, data interpretation and review drafting.

Rao Sun (SR): protocol drafting, search strategy development, acquiring trial reports, trial selection and review drafting.

Sai GE (GS): protocol drafting, search strategy development, data extraction, data analysis, data interpretation and review drafting.

Zongjiu Zhang (ZZ): protocol drafting, search strategy development, acquiring trial reports, trial selection, data extraction, data analysis, data interpretation and review drafting.

Declarations of interest

None known

Differences between protocol and review

Timing of outcome measurement: changed from "Short-term: 1 to 4 weeks, medium-term: more than 4 weeks to 12 weeks" to "Short-term: 1 to 6 weeks, medium-term: more than 6 weeks to 12 weeks".

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Anton 2008

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: (1) be a healthy female without any chronic disease, (2) be a carbohydrate craver, determined by self-reported carbohydrate cravings on 2 or more days of the week, (3) be >18 and <50 years of age, (4) have a BMI between 25 and 39.9 kg/m2 and (5) be a non-smoker.

Exclusion criteria: participants were excluded if they had a diagnosable eating disorder or were taking any medications or dietary supplements (including CrP) that could influence appetite, hunger or satiety.

Diagnostic criteria: BMI

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: food intake at breakfast, lunch and dinner was directly measured; hunger levels, fat cravings and body weight
Study details

Run-in period: 8 weeks

Study terminated before regular end: not stated

Publication details

Language of publication: English

Non-commercial funding: this research was supported by the Health and Performance Enhancement Division of the Pennington Biomedical Research Center

Publication status: peer review journal

Stated aim for studyQuote: "To assess the effect of CrPic in modulating food intake in healthy, overweight, adult women who reported craving carbohydrates"
NotesAbbreviations: BMI: body mas index; CrP: chromium picolinate
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear risk

Participants were randomly assigned to receive either 1000 μg of chromium as CrP or placebo

Comment: no detail is given on the methodology

Allocation concealment (selection bias)Unclear riskComment: no detail is given
Blinding of participants and personnel (performance bias)
Objective outcomes
Unclear riskComment: just mentions ''double-blind"; detailed information not provided
Blinding of participants and personnel (performance bias)
Subjective outcomes
Unclear riskComment: just mentions ''double-blind"; detailed information not provided
Blinding of outcome assessment (detection bias)
Objective outcomes
Unclear riskComment: just mentions ''double-blind"; detailed information not provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Unclear riskComment: just mentions ''double-blind"; detailed information not provided
Incomplete outcome data (attrition bias)
Objective outcomes
Low risk

Quote: "One participant in the placebo group dropped out of the study because of an adverse emotional reaction reportedly due to the study medication." No other adverse events were reported.

Comment: nothing was detected

Incomplete outcome data (attrition bias)
Subjective outcomes
Low risk

Quote: "One participant in the placebo group dropped out of the study because of an adverse emotional reaction reportedly due to the study medication." No other adverse events were reported.

Comment: nothing was detected

Selective reporting (reporting bias)Low riskComment: the study protocol is not available
Other biasUnclear riskComment. the trial had a commercial source of funding possibly creating a risk of bias

Campbell 1999

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: men, age range 50 to 75 years; BMI range 27 to 34 kg/m2; non-diabetic; physically able to safely engage in all aspects of the study protocol; clinically normal cardiac function, blood pressure, liver function and kidney function

Exclusion criteria: not stated

Diagnostic criteria: not stated

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: body weight, each man’s baseline maximal strength for each exercise was set as the greater of two one-repetition-maximum values obtained during the first two resistance exercise sessions; urinary creatinine excretion (P < 0.001), muscle strength (P < 0.001), arm-pull muscle power, knee-extension muscle power, fat-free mass (P < 0.001), whole body muscle mass (P < 0.001) and vastus lateralis type II fibre area (P < 0.05)
Study details

Run-in period: 13 weeks

Study terminated before regular end: no

Publication details

Language of publication: English

Commercial / non-commercial / other funding: supported by National Institute on Aging Grants T32 AG-0048, 1-R29-AG-13409 and RO1-AG-11811, by General Clinical Research Center Grant MO1-RR-10732, and by an independent monetary gift from Nutrition 21

Publication status: peer review journal

Stated aim for studyQuote: "To assess the effect of high-dose chromium picolinate supplementation on body composition, including body density, whole body muscle mass and muscle"
NotesAbbreviations: BMI: body mass index; Cr: creatinine
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear risk

"Each man was randomly assigned in a double-blind fashion to either a chromium picolinate group or a placebo group"

Comment: no detail is given on the methodology

Allocation concealment (selection bias)Unclear riskComment: no details provided
Blinding of participants and personnel (performance bias)
Objective outcomes
Unclear riskComment: no details provided
Blinding of participants and personnel (performance bias)
Subjective outcomes
Unclear riskComment: no details provided
Blinding of outcome assessment (detection bias)
Objective outcomes
Unclear riskComment: no details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Unclear riskComment: no details provided
Incomplete outcome data (attrition bias)
Objective outcomes
Low risk

Eighteen of 23 men successfully completed the study protocol. The reasons for the five men withdrawing included the following: 1) a request by a participant’s personal physician to avoid aggravation of a chronic hip injury; 2) an irritation of chronic elbow tendonitis, unrelated to resistance exercise; 3) a personal family commitment; 4) a resistance exercise-induced aggravation of an existing knee condition; and 5) a shoulder injury caused by slipping on ice.

Comment: The primary outcome data were all reported

Incomplete outcome data (attrition bias)
Subjective outcomes
Unclear riskComment: no details provided
Selective reporting (reporting bias)Low risk

Comment: the study protocol is not available

Comment: nothing was detected

Other biasUnclear riskComment: the trial had a commercial source of funding possibly creating a risk of bias

Iqbal 2009

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: non-diabetic population aged 18 to 75 years with metabolic syndrome and abdominal adiposity; participants' eligibility required waist circumference ≥ 102 cm for men and ≥ 89 cm for women and at least two of the following: systolic blood pressure ≥ 130 mm Hg or diastolic blood pressure ≥ 85 mm Hg or taking ≥ 1 antihypertensive agent; fasting blood glucose ≥ 6.1 mmol/L, but < 7 mmol/L; fasting triglycerides ≥ 1.68, but ≤ 8.96 mmol/L; or HDL-C ≤ 1 mmol/L for males and ≤ 1.29 mmol/L for females

Exclusion criteria: 2-hour plasma glucose value of ≥ 11.1 mmol/L, ASCVD, LDL-C > 4.9 mmol/L, liver transaminases three times the upper limit of normal, renal insufficiency, fibrates or dietary supplements (excluding a multivitamin with < 100 μg chromium)

Diagnostic criteria: waist circumference, BMI, according to the criteria of the National Cholesterol Education Program Adult Treatment Panel III

Interventions

Number of study centres: 1

Treatment before study: not reported

Titration period: not reported

Outcomes Outcomes reported in abstract of publication: insulin sensitivity index derived from a frequently sampled intravenous glucose tolerance test. Prespecified secondary endpoints included changes in other measurements of glucose metabolism, oxidative stress, fasting serum lipids and high sensitivity C-reactive protein
Study details

Run-in period: 16 weeks

Study terminated before regular end: no

Publication details

Language of publication: English

Commercial and non-commercial funding: this work was supported by the following grants: R21DK067241, K-23 AT-00058, and M01-RR00040 (Translational Research Center [TRC]). Nutrition 21 provided active drug and placebo. Dr Boston is the principal author of the modelling software MinMod Millenium

Publication status: peer review journal

Stated aim for studyQuote: "To determine the effects of chromium picolinate (CrP) on glucose metabolism in patients with metabolic syndrome"
NotesAbbreviations: BMI: body mass index
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear risk

Quote: "conducted a randomised, double-blind, placebo-controlled study of the safety and efficacy of 16 weeks of CrPic therapy and randomised in a 1:1 double-blind fashion to receive either CrPic or matching placebo."

Comment: No other details given

Allocation concealment (selection bias)Unclear riskComment: method of concealment is not described
Blinding of participants and personnel (performance bias)
Objective outcomes
Unclear riskComment: method of blinding is not described
Blinding of participants and personnel (performance bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Blinding of outcome assessment (detection bias)
Objective outcomes
Unclear riskComment: no details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Incomplete outcome data (attrition bias)
Objective outcomes
Low riskComment: three participants withdrew for personal reasons
Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskComment. no subjective outcomes
Selective reporting (reporting bias)Low riskComment: the study protocol is available and there was no selective reporting
Other biasUnclear riskComment: the trial had a commercial source of funding possibly creating a risk of bias

Joseph 1999

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: moderately overweight older men and women (aged 54 to 71 years; BMI 26 to 36 kg/m2) who were not actively involved in any physical training volunteered to participate in this 13-week study

Exclusion criteria: included populations with any metabolic or cardiac abnormalities. When this study was performed, the 1979 recommendations of the National Diabetes Data Group (NDDG) 21 were used to exclude diabetics at screening. Populations with fasting plasma glucose greater than 7.77 mmol/L or 2-hour OGTT plasma glucose > 11.1 mmol/L and one additional 0 to 120-minute plasma glucose sample > 11.1 mmol/L were deemed diabetic and were excluded from the study

Diagnostic criteria: according to the criteria of The National Diabetes Data Group (NDDG)

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

RT consisted of 12 weeks of progressive RT twice weekly with a minimum of days, rest between training sessions

Outcomes Outcomes reported in abstract of publication: weight, body fat, fat mass, fat free mass, basal plasma glucose or insulin levels, glycosylated haemoglobin, triglycerides, total cholesterol, LDL-C, HDL-C
Study details

Run-in period: 13 weeks

Study terminated before regular end: no

Publication details

Language of publication: English

Non-commercial funding: Supported by National Institutes of Health Grants No. 1-R29-AG13409 and RO1-AG11811, National Institute on Aging Grant No. T32-AG00048, an independent monetary gift from Nutrition 21, San Diego, CA, and General Clinical Research Center Grant No. MO1-RR10732.

Publication status: peer review journal

Stated aim for studyQuote: "To assess the effect of 12 weeks of resistance training (RT) with or without chromium picolinate (CrP) supplementation on glucose tolerance in moderately overweight older men and women"
Notes-
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Low riskComment: randomised; computer-generated randomisation list
Allocation concealment (selection bias)Low riskComment: hospital pharmacy
Blinding of participants and personnel (performance bias)
Objective outcomes
Low riskQuote: "... a double-blind fashion, all capsules, including placebo, were furnished by our hospital pharmacy and were indistinguishable from each other. Neither the researchers nor the patients knew into which group they had been randomised"
Blinding of participants and personnel (performance bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Blinding of outcome assessment (detection bias)
Objective outcomes
Low riskQuote: "All capsules, including placebo, were furnished by our hospital pharmacy and were indistinguishable from each other. Neither the researchers nor the patients knew into which group they had been randomized. Independent pharmacists dispensed either chromium capsules or placebo in numbered containers according to a computer-generated randomization list. No restrictions were used"
Blinding of outcome assessment (detection bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Incomplete outcome data (attrition bias)
Objective outcomes
Low riskComment: no data missing
Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Selective reporting (reporting bias)Low riskComment: all of the outcomes listed in the methods section were reported as results
Other biasLow riskComment: no other details given to assess whether an important risk of bias exists

Kaats 1996

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: adults consulting their personal physician

Exclusion criteria: not stated

Diagnostic criteria: not stated

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: body composition, body weight, percentage body fat, non-fat mass and body composition improvement
Study details

Run-in period: 72 days

Study terminated before regular end: not stated

Publication details

Language of publication: English

Commercial funding: "Funding for the study was provided by the Living at Goal Weight Center, San Antonio, Texas; Optimal Health Products, San Antonio, Texas; and Nutrition 21, Inc., San Diego, California."

Publication status: peer review journal

Stated aim for studyQuote: "To examine the effect of chromium picolinate (CrP) on body composition"
Notes-
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: randomised, but method not stated
Allocation concealment (selection bias)Unclear riskComment: not reported
Blinding of participants and personnel (performance bias)
Objective outcomes
Low riskComment: none of the investigators, research technicians dispensing the product or populations knew which code corresponded to the amount of CrP in the canister
Blinding of participants and personnel (performance bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Blinding of outcome assessment (detection bias)
Objective outcomes
Low riskComment: not details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Unclear riskComment: no subjective outcomes
Incomplete outcome data (attrition bias)
Objective outcomes
Unclear risk

Quote: "Some concerns may be raised about the relatively high dropout rate in our study - 69 of 219 (31.5%). A comparison of their initial body composition scores revealed no significant difference between the three groups nor between any of the three groups of patients who completed or failed to complete the protocol"

Comment: unclear influence of attrition rate

Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskComment. no subjective outcome
Selective reporting (reporting bias)Low riskComment: all of the outcomes listed in the methods section were reported as results
Other biasUnclear riskComment: the trial had a commercial source of funding possibly creating a risk of bias

Kaats 1998

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: adults consulting their personal physician

Exclusion criteria: not stated

Diagnostic criteria: not stated

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: body weight, percentage body fat, fat mass and fat-free mass
Study details

Run-in period: 90 days

Study terminated before regular end: no

Publication details

Language of publication: English

Commercial funding: this study has been supported financially by Nutrition 21, Inc., San Diego, California

Publication status: peer review journal

Stated aim for studyQuote: "To determining whether the body composition changes observed in the initial study could be replicated in this study"
Notes 
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear riskComment: randomised, but method not stated
Allocation concealment (selection bias)Low riskComment: independent local pharmacist
Blinding of participants and personnel (performance bias)
Objective outcomes
Low riskQuote: "None of the investigators, research technicians dispensing the product, or participants knew which participant's number corresponded to the placebo or active product. An independent local pharmacist acted as trustee for the study and randomly assigned participant's numbers to bottles that had been prelabeled with either an “X” or “Y” to correspond with either active product or placebo"
Blinding of participants and personnel (performance bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Blinding of outcome assessment (detection bias)
Objective outcomes
Low riskComment: not details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Incomplete outcome data (attrition bias)
Objective outcomes
Low riskComment: no dropouts
Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Selective reporting (reporting bias)Low riskComment: all of the outcomes listed in the methods section were reported as results
Other biasUnclear riskComment: the trial had a commercial source of funding possibly creating a risk of bias

Kleefstra 2006

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: Individuals with type 2 diabetes, glycosylated haemoglobin (A1c) ≥ 8%, daily use of insulin ≥ 50 units, creatinine ≤ 150 μmol/L for men and ≤ 120 μmol/L for women, creatinine clearance ≥ 50 ml/min, alanine aminotransferase ≤ 90 units/L and age < 75 years

Exclusion criteria: included pregnancy, or intention to become pregnant during the study, and a history of liver or renal disease

Diagnostic criteria: BMI, A1c

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: A1c, BMI, blood pressure, lipid profile and insulin requirement.
Study details

Run-in period: 6 months

Study terminated before regular end: no

Publication details

Language of publication: English

Commercial / non-commercial / other funding: not stated

Publication status: peer review journal

Stated aim for studyQuote: "To determine the effect of chromium treatment on glycemic control in a western population of insulin-dependent patients with type 2 diabetes".
NotesAbbreviations: BMI: body mass index
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Low riskComment: computer-generated randomisation list
Allocation concealment (selection bias)Low riskComment: independent pharmacists dispensed either chromium capsules or placebo in numbered containers according to a computer-generated randomisation list.
Blinding of participants and personnel (performance bias)
Objective outcomes
Low riskQuote: "All capsules, including placebo, were furnished by our hospital pharmacy and were indistinguishable from each other. Neither the researchers nor the patients knew into which group they had been randomised"
Blinding of participants and personnel (performance bias)
Subjective outcomes
Unclear riskQuote: "All capsules, including placebo, were furnished by our hospital pharmacy and were indistinguishable from each other. Neither the researchers nor the patients knew into which group they had been randomised"
Blinding of outcome assessment (detection bias)
Objective outcomes
Low riskComment: no details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Unclear riskComment: no details provided
Incomplete outcome data (attrition bias)
Objective outcomes
Low riskComment: no attrition bias was detected
Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskQuote: "Of 53 patients randomised, 1 patient was lost to follow-up, and all attempts to locate this participant were in vain (telephone contact, letters, and visits). Six other individuals, one in the placebo group, three in the 500 µg group, and two in the 1,000 µg group, discontinued the study for the following reasons: one patient required a blood transfusion and was hospitalised, and three other patients were hospitalised due to percutaneous transluminal coronary angioplasty, chronic obstructive pulmonary disease, and glycemic dysregulation.Two patients discontinued the study due to possible adverse effects. Unfortunately, intention-to-treat analyses were not possible because for five of six excluded patients follow-up data were lacking. However, the main conclusions of the per-protocol analyses would likely not have been different in an intention-to-treat analyses"
Selective reporting (reporting bias)Low riskComment: all of the outcomes listed in the methods section were reported as results
Other biasLow riskComment: no other details given to assess whether an important risk of bias exists

Volpe 2001

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: 44 female participants, with a BMI between 27 and 41 kg/m2, between 27 and 51 years of age, premenopausal, sedentary, not taking any dietary supplements, not taking any vitamin or mineral supplements containing chromium, not on a weight-loss programme, not taking any weight loss supplements, non-smoking and with no history of chronic diseases or recent acute illness. Participants were asked not to alter their dietary habits during the course of the study

Exclusion criteria: not stated

Diagnostic criteria: BMI

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: body composition, resting metabolic rate, fasting plasma glucose, serum insulin, plasma glucagon, serum C-peptide and serum lipid concentrations or iron and zinc indices, serum total cholesterol concentration, exercise training
Study details

Run-in period: 12 weeks

Study terminated before regular end: no

Publication details

Language of publication: English

Commercial and non-commercial funding: "the authors would like to thank Nutrition 21 (San Diego, CA) for funding this project. This research is based upon work partially supported by the Cooperative State Research Extension, Education Service, U.S. Department of Agriculture Experiment Station, under Project No. MAS00757 Manuscript No. 3280"

Publication status: peer review journal

Stated aim for studyQuote: "To investigate the effect of chromium picolinate (CP) supplementation on body composition, resting metabolic rate (RMR), selected biochemical parameters and iron and zinc status in moderately obese women participating in a 12-week exercise program"
NotesAbbreviations: BMI: body mass index
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear risk

Quote: "Forty-four free-living females were assigned, in a stratified randomised manner based on their BMI, to one of two groups"

Comment: no other details given

Allocation concealment (selection bias)Unclear riskComment: not reported
Blinding of participants and personnel (performance bias)
Objective outcomes
Unclear risk

Quote from publication: "double-blind"

Comment: no other details given

Blinding of participants and personnel (performance bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Blinding of outcome assessment (detection bias)
Objective outcomes
Low riskComment: no details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Unclear riskComment: no details provided
Incomplete outcome data (attrition bias)
Objective outcomes
Unclear riskQuote: "Thirty-seven of the initial 44 people (84%) completed this study. Sixteen people reported forgetting to take their capsules and 13 people missed exercise training; however, no people reported forgetting to take the capsules more than five days (average 3 days) during the study period. Furthermore, none of these people missed exercise training more than four times (average 3) during the entire study. Two people did have minor problems with their knees or ankles, so they were unable to perform all of the specified weight training exercises (e.g. leg extension and calf raises)"
Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskComment: no subjective outcome
Selective reporting (reporting bias)Low riskComment: all of the outcomes listed in the methods section were reported as results
Other biasUnclear riskComment: the trial had a commercial source of funding possibly creating a risk of bias

Yazaki 2010

Methods Parallel randomised controlled clinical trial
Participants

Inclusion criteria: overweight (BMI > 25 kg/m2) non-smoking adults aged 25 to 75 years with abdominal adiposity (waist circumference > 80 cm in females and > 100 cm in males)

Exclusion criteria: contraindication to abdominal computed tomography scans (weight > 375 pounds, claustrophobia, unstable vital signs, or radiation procedure in past six months), diagnosed diabetes, diagnosed eating disorder, uncontrolled hypertension, emphysema, intestinal or stomach disease, kidney disease, substance abuse, pregnancy or intention to become pregnant during the study

Diagnostic criteria: BMI, waist circumference measures

Interventions

Number of study centres: 1

Treatment before study: not stated

Titration period: not stated

Outcomes Outcomes reported in abstract of publication: weight, height, blood pressure, percentage body fat, serum and urinary biomarkers
Study details

Run-in period: 24 weeks

Study terminated before regular end: no

Publication details

Language of publication: English

Commercial funding: supported by Nutrition 21, Inc

Publication status: peer review journal

Stated aim for studyQuote: "Assess the effects of chromium picolinate supplementation, alone and combined with nutritional education, on weight loss in healthy overweight adults"
NotesAbbreviations: BMI: body mass index
Risk of bias
BiasAuthors' judgementSupport for judgement
Random sequence generation (selection bias)Unclear risk

Quote: "People were enrolled and randomized using balanced allocation within gender"

Comment: no details provided

Allocation concealment (selection bias)Low riskQuote: "People and study personnel were blinded to the intervention. Chromium and placebo were prepackaged and shipped from the manufacturer to the study site. Bottles were labelled and coded by an unblinded individual unaffiliated with the study. Investigators thus only knew the treatment assignment (group A or B) of the people without knowledge of whether these contained chromium or placebo"
Blinding of participants and personnel (performance bias)
Objective outcomes
Low riskQuote: "People and study personnel were blinded to the intervention. Chromium and placebo were prepackaged and shipped from the manufacturer to the study site. Bottles were labelled and coded by an unblinded individual unaffiliated with the study. Investigators thus only knew the treatment assignment (group A or B) of the people without knowledge of whether these contained chromium or placebo"
Blinding of participants and personnel (performance bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Blinding of outcome assessment (detection bias)
Objective outcomes
Low riskComment: no details provided
Blinding of outcome assessment (detection bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Incomplete outcome data (attrition bias)
Objective outcomes
Unclear riskComment: insufficient reporting of attrition/exclusions to permit judgement  
Incomplete outcome data (attrition bias)
Subjective outcomes
Low riskComment: no subjective outcomes
Selective reporting (reporting bias)Low riskComment: the study protocol is not available
Other biasUnclear riskComment: the trial had a commercial source of funding possibly creating a risk of bias

Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion
Albarracin 2008Combination therapy of chromium picolinate and biotin versus placebo
Bunting 1994Animal study
Diaz 2008Combination therapy of chromium picolinate and conjugated linoleic acid in tonalin oil versus placebo and canola oil
Docherty 2005Participants not obese or overweight
Earle 1989Participants not obese or overweight
Geohas 2007Combination therapy of chromium picolinate and biotin versus placebo
Hoeger 1998Combination therapy of chromium picolinate, inulin, capsicum, L-phenylalanine and other lipotropic nutrients versus placebo
Joyal 2004Not a randomised trial
Pasman 1997Not a randomised trial
Pittler 2004Not a randomised trial
Rabinowitz 1983Participants not obese or overweight
Stupar 1999Not a randomised trial
Trent 1995Participants not obese or overweight
Wang 2010Not a randomised trial
Wilson 1995Participants not obese or overweight
Zenk 2007Combination therapy investigating 3-acetyl-7-oxo-dehydroepiandrosterone alone (7-Keto) and in combination with calcium citrate, green tea extract, ascorbic acid, chromium nicotinate and cholecalciferol (HUM5007) versus placebo

Ancillary