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Keywords:

  • Youth;
  • diet;
  • physical activity;
  • environment

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

An extensive body of research exists on environmental influences on weight-related behaviours in young people. Existing reviews aimed to synthesize this body of work, but generally focused on specific samples, behaviours or environmental influences and integration of findings is lacking. Hereto, we reviewed 18 reviews representing 671 unique studies, aiming to identify what environmental factors do and do not affect physical activity and dietary behaviours in children and adolescents. Eleven reviews focused exclusively on physical activity, six on diet, and one review focused on both physical activity and dietary behaviours with only small overlap in included studies. Physical activity was more consistently related to school and neighbourhood characteristics than to interpersonal and societal environments. In contrast, interpersonal factors played a pronounced role in dietary behaviours; no school, neighbourhood or societal factors were consistently related to dietary behaviours. This review of reviews adds to the literature by providing a comprehensive synthesis of factors related to physical activity and dietary behaviours that could be targeted in interventions. Moreover, by identifying factors that are unrelated to physical activity and dietary behaviours, this review may help to narrow the scope of future studies and environmental interventions.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

Overweight and obesity are serious public health challenges and prevalence rates have tripled since the 1980s (1). Increases in rates of overweight and obesity have been particularly alarming in children and adolescents; annual increases in prevalence rates today are tenfold those of the 1970s (1). Currently, about one-third of European youth is overweight (2). Childhood overweight is an important predictor of adult overweight; over 60% of children who are overweight before puberty will be overweight in early adulthood (3). Childhood overweight has important consequences for morbidity, disability and quality of life in adulthood. Furthermore, childhood overweight is associated with risk factors for cardiovascular diseases and diabetes, orthopaedic problems and mental disorders during childhood, and may lead to school underachievement and lower self-esteem (4).

Overweight is the result of a long-term energy imbalance characterized by energy intake (through diet) exceeding energy expenditure (mainly from physical activity). As such, physical activity and dietary behaviours are the main determinants of overweight. Unfavourable longitudinal and secular trends have been observed in dietary and physical activity behaviours among youth. Whereas fruit and vegetable intake declines with age (5), fast food intake increases through adolescence (6). Additionally, the amount and frequency of consumption of snacks and fast food has increased in the past decade (6,7). Similarly concerning trends have been reported for physical activity, which declines with age during youth and from youth to adulthood (8,9). Although physical activity and sedentary pastime do not appear to have changed dramatically across generations, physical activity levels are generally low, whereas much time is spent in sedentary activities (10–13).

Changes in physical activity and dietary behaviours among youth are commonly ascribed to environmental features that encourage excess energy intake and discourage energy expenditure. The energy imbalance that promotes overweight is fuelled by an unsupportive environment, with ever increasing portion sizes, high availability of energy-dense and high-palatable foods and lower accessibility of healthy alternatives (14). The sum of influences outside the individual that surroundings, opportunities or conditions of life have on promoting obesity in individuals and populations has been referred to as the obesogenic environment (15).

A multitude of environmental features (i.e. all factors outside the individual) may play a role in weight and weight-related behaviours. Various theories and frameworks have been proposed to conceptualize this multitude of environmental influences. Social Ecological Theory (16) and Ecological Systems Theory (17) are general models of environmental influences on behaviour, whereas the Analysis Grid for Environments Linked to Obesity (ANGELO) framework (15), the Environmental Research framework for weight Gain prevention (EnRG) framework (18) and the contextual model of childhood overweight (19) specifically describe environmental factors that influence overweight and obesity. These different models have in common that they distinguish interpersonal (e.g. peers and family), organizational (e.g. schools), community (e.g. neighbourhood) and societal influences (e.g. food price and marketing) on behaviours. Moreover, influences at these different levels may interact, thereby enhancing or diminishing each level's separate effects on weight-related behaviours and weight status.

In recent years, the number of studies exploring the impact of environmental factors on physical activity and dietary behaviours, including in children and adolescents, has grown rapidly. Despite the large number of individual studies on environmental factors linked to obesity, it remains to be established whether some environmental factors are more important than others or whether the influences of some environments are better understood than those of others (20). In particular, it remains unknown whether some factors are consistently related to diet or physical activity, but also whether some factors are consistently unrelated to physical activity and dietary behaviours. In addition to understanding which environmental factors are related to diet or physical activity, it is also important to understand which factors are unrelated, as this will help to narrow the scope of future environmental factors that need to be addressed in research and environmental interventions. Moreover, despite the growing body of research on environmental influences on overweight, a comprehensive, systematic integration of findings is lacking. Several reviews have been conducted to date but each of these adopted their own specific approach, with a focus on particular types of environmental influences, on particular types of outcomes or on specific samples. An integration of findings regarding the wide range of environmental correlates of weight-related behaviours among youth is lacking. We aimed to fill this important gap by conducting a systematic review of reviews to integrate findings on environmental correlates that do and do not influence physical activity or dietary behaviours that will contribute to a comprehensive synthesis of research and help to identify fruitful avenues for future investigation.

The focus is specifically on environmental correlates of physical activity and dietary behaviours among youth. Because children and adolescents have less autonomy in their behavioural choices, exploring environmental influences might be specifically relevant for youth (21,22). Moreover, youth might be more often exposed to particular types of environmental influences, such as influences in the school setting or peer influences. As this might also vary across age groups, potential differences in environmental influences for children and for adolescents will be explored.

Methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

Identification of relevant studies

The literature was searched to identify relevant reviews, including systematic reviews as well as meta-analyses. Three electronic databases were searched to identify reviews of environmental correlates of weight-related behaviours and outcomes (EMBASE, Pubmed, Psychinfo) published until June 2009. Broad and more specific search terms were used that related to weight-related behaviours (physical activity, exercise, diet, nutrition, eating, food), weight (overweight, obesity), the social environment (socio-cultural, socioeconomic, cultural, social) and the physical environment (built environment, urban environment, school environment). Criteria for inclusion of papers were that they (i) reported a systematic review or meta-analysis; (ii) reported on studies performed in humans younger than 18 years and (iii) were published in English. Reviews of intervention studies were excluded, as were reviews that did not describe the search strategy or inclusion/exclusion criteria. Also excluded were reviews that focused exclusively on studies of infants, toddlers or pre-schoolers, and studies that did not separately present results for young people and adults. Identified papers were first screened for inclusion based on the title, followed by a screening of the abstract, and then the full text. The reference lists of included papers were screened for further relevant studies. Any duplicate papers were removed.

Data extraction

Data were separately extracted for reviews of physical activity and dietary behaviours. From each individual review, the following information was obtained: objectives, number of included studies, inclusion and exclusion criteria, environmental correlates, outcome measures and findings. To be consistent with previous reviews, findings were analysed separately for environmental factors at the interpersonal, organizational (school), community (neighbourhood) and macro or societal levels. To review the reviews, a two-step approach was used. First, findings regarding environmental correlates were extracted from each included review separately. The methods for analysing the data varied across reviews. To make sure that findings are interpreted in a similar way across reviews, we re-analysed all individual reviews in the same way. We adopted the approach that was used most often in the included reviews (e.g. (23,24)). Findings for each environmental correlate were coded to indicate a positive, negative or no association, when the correlate was included in at least three studies and results were in the same direction in at least 60% of the studies. When the correlate was included in at least three studies, but results were not consistent in 60% of the studies, the coding indicated mixed results. Second, comparable correlates (e.g. different operationalizations of the same factor) were grouped together under the heading of broader environmental factors. To further integrate findings across reviews, environmental factors for which a majority of the individual reviews reported findings that were in the same direction were labelled as having a positive, negative or no association with weight-related behaviours of young people. Else, findings for environmental factors were labelled as mixed.

Age was explored as a moderator of the association between environmental factors and physical activity or dietary behaviours. If individual reviews allowed, findings were summarized separately for children (aged <12 years) and adolescents (age >12 years).

Quality rating

The included reviews were rated for methodological quality based on eight criteria (i) inclusion of an explicit and clear statement regarding the search strategy that was employed; (ii) comprehensiveness of the search strategy, with at least two databases searched, as well as the reference lists of examined papers; (iii) clarity of the description of inclusion and exclusion criteria; (iv) inclusion of a clear description of the design and the number of studies that were included; (v) report of a quality assessment; (vi) the quality assessment included ratings of at least two of the following aspects: study design, sampling, outcome measures and follow-up assessment; (vii) integration of the findings beyond describing or listing primary studies and (viii) involvement of more than one author in the data abstraction and research synthesis process. Individual reviews were awarded one point for each of the criteria, resulting in a quality score that could range from 0 to 8. Reviews with quality scores ranging from 0 to 4 were labelled as weak. Reviews were labelled as strong if their quality score was between 5 and 8. These quality criteria are similar to those used in previous systematic reviews of reviews (25,26), and were based on the Quality Assessment Tool for Reviews (27) and the Centre for Reviews and Dissemination criteria for quality assessment of reviews (28).

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

Identification of reviews

The literature search initially identified 816 titles (Pubmed 773, Psychinfo 27, Medline 16). The screening of titles and abstracts of papers identified in the different databases resulted in a selection of 132 publications. Four duplicates were removed, leaving 128 publications for full-text review. Sixteen reviews met the inclusion criteria. Two additional reviews were identified in the reference lists. Main reasons for exclusion were that reviews described the relation between weight-related behaviours and weight without explicitly considering environmental correlates, or that they reflected narrative reviews that did not report any search strategy.

Of the 18 reviews that were included, 11 focused exclusively on physical activity, six on diet, and one review focused on both physical activity and dietary behaviours. In Table S1, the number of included studies, inclusion and exclusion criteria, outcome measures, environmental correlates and findings are described for each review of physical activity. Table S2 provides similar information for each of the reviews of dietary behaviours.

Description of reviews of physical activity in young people

A total of 12 reviews were identified that addressed environmental correlates of physical activity. Seven of these 12 reviews (21,23,29–33) received a quality rating of five or higher and were rated as strong (See Table 1). The number of studies included in the separate reviews ranged from 13 to 150 (Table 1). Together the reviews included 656 studies. The reviews represented 439 unique studies after correcting for studies that are included in more than one review.

Table 1.  Quality assessment of reviews of environmental correlates of physical activity in young people
Quality assessment criteriaWas there a clearly defined search strategy?Was the search strategy comprehensive?*Are inclusion/exclusion criteria clearly stated?Are the designs and number of included studies clearly stated?Has the quality of primary studies been assessed?Did the quality assessment include study design, study sample, outcome measures or follow-up (at least 2 of 4)Does the review integrate findings beyond describing or listing findings of primary studies?Has more than one author been involved in the data abstraction process?Sum quality scoreNo. of included studies
  • *

    A search is rated as comprehensive if at least two databases and the reference lists of examined papers were searched.

Davison et al., 2008 (35)+++3 (weak)20
Davison & Lawson, 2006 (29)++++++6 (strong)33
Ferreira et al., 2006 (21)++++++6 (strong)150
Gorely et al., 2004 (30)+++++5 (strong)68
Gustafson & Rhodes, 2006 (31)+++++5 (strong)34
Hanson & Chen, 2007 (32)++++++6 (strong)34
Van der Horst et al., 2007 (33)+++++5 (strong)57
Limstrand, 2008 (36)++++4 (weak)43
Pugliese & Tinsley, 2007 (34)++++4 (weak)31
Ridgers et al., 2006 (37)+++3 (weak)13
Sallis et al., 2000 (23)+++++5 (strong)108
Tomkinson & Olds, 2007 (38)++++4 (weak)65

Seven reviews focused on general physical activity as the primary outcome measure (21,23,29,31–34). One review additionally addressed correlates of sedentary behaviour (33). Five reviews focused on specific types of physical (in)activity, such as active commuting (35), TV/Video viewing (30), use of sports facilities (36), physical activity during school play time (37) or fitness test performance (38). Differences were also found in the type of correlates that were reviewed. Six reviews made no a priori selection of the type of environmental correlates (21,23,30,33,35,36), whereas six other reviews focused on specific types of environments, such as the physical environment (29), parental influences (31,34), socioeconomic status (SES) (32), school play time (37) or geographic variables (38). The reviews included young people of varying age, but in most reviews sample age was between 2 and 19 years (21,23,30,31,33–36,38). An age range of 10–21 years old was defined by Hanson and Chen (32), and Ridgers et al. (37) reported on young people aged 4–12 years.

Systematic review of environmental correlates of physical activity in young people

The findings of the reviews of physical activity are summarized in Table 2. First, environmental correlates for which consistently positive or negative associations were found are described followed by correlates that were consistently unrelated to physical activity.

Table 2.  Overview of findings from reviews of environmental correlates of physical activity in young people
FactorOperationalization+0?
  1. Numbers in italics are reviews that were rated as weak.

  2. Numbers correspond to individual reviews: 1 = Davison et al., 2008 (35); 2 = Davison & Lawson, 2006 (29); 3 = Ferreira et al., 2006 (21); 4 = Gorely et al., 2004 (30); 5 = Gustafson & Rhodes, 2006 (31); 6 = Hanson & Chen, 2007 (32); 7 = Van der Horst et al., 2007 (33); 8 = Limstrand, 2008 (36); 9 = Pugliese & Tinsley, 2007 (34); 10 = Ridgers et al., 2006 (37); 11 = Sallis et al., 2000 (23); 12 = Tomkinson & Olds, 2007 (38).

  3. +, positive association; 0, no association; −, negative association; ?, mixed results.

  4. a, adolescents; c, children; SES, socioeconomic status.

Interpersonal     
 SESFamily SES87a, 3a 5,6, 3c
Parental occupational status 9,3c,3a13c,a,4
parental education4,7a,3a3c,a, 7c 3c
Family income3a   
 Family sizeSingle parent household 3c,a,7c4 
Number of household members 3c,a  
 Modelling parentsParents'/mother's physical activity9,1,83c,a,7a,11a 5,7c,11c,3c,a
Number of active parents5   
Parents' instrumental behaviours9,11a11c  
Parents' TV viewing habits  4 
 Modelling othersSibling physical activity11a3a  
Friends' physical activity 3c,a,11a  
Peer influence 11c  
 Parental supportParenting styles 3c,a  
Parental encouragement93c,11c 3a
Parental support5,7c,83c,9,11a 3a
 Support of othersFriends' support7a,83a 11a
Support of significant others11a  3a
 Social normsSocial norms 3c 3a
 Home facilitiesFamily car ownership 1,3c 8
Family dog ownership 3a  
Home equipment for activity82,3c,3a,7c,7a,11a  
TV set in bedroom  4 
School     
 School typePublic vs. private3c3a 1
High school vs. vocational/alternative3a   
 School locationLarge distance to school  1,2 
Low population density  1 
Large school enrolment 21 
School urbanization level 8  
 School facilitiesInstruction on sport/health benefits 3a  
School physical education programmes/school sports7a3a,12  
Equipment school play areas2   
Time allowed for free play/field trips3c,10   
 School supportTeacher support 11a 3a
School support 3a  
Coach support/modelling 11a  
Problems with classmates/teasing   3a
Teacher physical activity 3a,11a  
 Teacher SESTeachers educational level3c   
Neighbourhood     
 SESNeighbourhood SES   3c
% upper occupational status 3a  
% dwellings provided by employer 3a  
% owner occupied housing   3a
% unemployment among residents   3a
Length of unemployment  3a 
 Residents' characteristicsInvolvement in community physical activity organizations 3c  
% married couples 3a  
% youth 3a  
Presence of neighbourhood exercisers 3a  
 InfrastructureRoad and sidewalk infrastructure1,2,83c  
Ease to cycle8   
Presence of bike lanes   2
System of streets with multiple routes and connections   2
Limited public transport   3c
 AccessibilityAccess to destinations (e.g. shops)2, 8   
Short distance8   
Proximity of playgrounds and parks8  2
 FacilitiesOpportunities to exercise11a   
Availability recreational facilities2,8,11c3c,a  
 Traffic safetyLow traffic density2   
Perceived traffic safety 1  
Safe roads 8  
 Personal safetyNeighbourhood hazards 3c  
Concerns for crime 1  
Perceived safety82,3c,a, 11c  
Low crime incidence3a   
Area deprivation and crime  2 
Dogs unattended 3a  
 AppearanceCondition8   
Number of trees/green space 8  
Area type/features/improvements8   
Aesthetics8   
Macro/societal     
 ClimateUnsuitable weather 1,283a
Month of the year (average temperature)  2,12 
Latitude12   
Season 8 3c,a,11c
Climate   8
Sun exposure  8 
 LocationRural residence 3a12,3c,4,11c
Population density   2
Urban vs. suburban   3c,a,8
Region within country 8  
 CultureNational exercise psyche12   
 MediaExposure to sports media 3a,11a  
Interpersonal level

None of the environmental correlates at the interpersonal were consistently positively or negatively related to physical activity. Modelling of friends and siblings, family size and home opportunities for physical activity (e.g. home equipment) were unrelated to physical activity across reviews.

School level

At the school level, teacher SES was positively related to physical activity, although only one review included teacher SES as a correlate. None of the school factors were negatively associated with physical activity across reviews. School support was unrelated to physical activity.

Neighbourhood level

Neighbourhood appearance, availability of exercise facilities and general accessibility (i.e. having easy access and short distances to common destinations) were positively related to physical activity across reviews. None of the neighbourhood factors were negatively related to physical activity. Across reviews, characteristics of neighbourhood residents, traffic safety and personal safety were unrelated to physical activity.

Societal or macro level

Exercise culture was positively related to physical activity, but only one review included this correlate. No macro or societal factors were negatively related to physical activity. Exposure to sports media was unrelated to physical activity in two reviews.

Summary of consistent findings for physical activity in young people based on strong reviews only

Below are consistent positive and negative correlates of dietary behaviours reported, as well as correlates that are consistently unrelated to dietary behaviours in young people. Only reviews rated as strong quality are included in this analysis.

Positive

Teacher SES, specific school types (i.e. public schools, higher level schools), school facilities for physical activity, neighbourhood facilities for physical activity and traffic safety were positively related to physical activity.

Negative

No factors were negatively related to physical activity.

Unrelated

Modelling of friends and siblings, support of parents, family size and home opportunities for physical activity, school support, characteristics of neighbourhood residents, personal safety and exposure to sports media were unrelated to physical activity.

Differences between children and adolescents

Six of the 12 reviews enable exploring the moderating role of age with respect to environmental influences on physical activity, but only for three types of environmental influences on physical activity (i.e. parental SES, parental modelling and parental support). For parental SES, all three reviews that compared findings on the relation between SES and physical activity in children and adolescents concluded that parental SES might be more relevant for adolescents than for children (21,32,33). Three reviews examined the moderating role of age of the relation between parental physical activity and young people's physical activity. In general, these reviews indicate that parental activity appears to be more important in childhood than in adolescence (21,32,33).

Three reviews examined the moderating role of age of the relation between parental supportive behaviours and physical activity in young people, but the results were inconclusive (23,31,34).

Description of reviews of dietary behaviours in young people

Seven reviews were identified that addressed environmental correlates of dietary behaviour (24,32,39–43). Five of these reviews (24,32,40,41,43) received a quality rating of five or higher and were rated as strong (see Table 3). The number of studies included in the separate reviews ranged from 7 to 99 (Table 3). All reviews combined included 298 studies. The reviews represented 232 unique studies after correcting for studies that are included in more than one review.

Table 3.  Quality assessment of reviews of environmental correlates of dietary behaviours in young people
Quality assessment criteriaWas there a clearly defined search strategy?Was the search strategy comprehensive?*Are inclusion/exclusion criteria clearly stated?Are the designs and number of included studies clearly stated?Has the quality of primary studies been assessed?Did the quality assessment include study design, study sample, outcome measures or follow-up (at least two of four)Does the review integrate findings beyond describing or listing findings of primary studies?Has more than one author been involved in the data abstraction process?Sum quality scoreNo. of included studies
  • *

    A search is rated as comprehensive if at least two databases and the reference lists of examined papers were searched.

Blanchette & Brug, 2005 (39)+++3 (weak)20
Hanson & Chen, 2007 (32)++++++6 (strong)30
Van der Horst et al., 2007 (24)++++++6 (strong)58
Pearson et al., 2009 (40)++++++6 (strong)24
Pearson et al., 2008 (41)+++++++7 (strong)60
Taylor et al., 2005 (42)++2 (weak)99
Woodruff & Hanning, 2008 (43)+++++5 (strong)7

Three reviews focused on healthy eating in general (32,42,43), whereas two other reviews specifically focused on fruit and vegetable consumption (39,41). One review focused on breakfast consumption (40). One review included fruit and vegetable consumption, fat intake, snacking and fast food, and soft drink intake (24). Differences also existed in the types of environmental correlates that were included in the review. Three reviews included environmental correlates at the interpersonal, school, neighbourhood and societal level (24,39,42). A further three reviews focused on family influences (40,41,43) and one review focused on SES (32). One review focused on children aged 6–12 (39), one focused on adolescents aged 13–19 (43) and one on the broader age group of 10–21 (32).

Systematic review of environmental correlates of dietary behaviours

The findings of the reviews of dietary behaviours are summarized in Table 4. Findings are reported in the same way as the findings for physical activity.

Table 4.  Overview of findings from reviews of environmental correlates of dietary behaviours in young people
FactorOperationalization+0?
  1. Numbers in italics are reviews that were rated as weak.

  2. Numbers correspond to individual reviews : 1 = Blanchette & Brug, 2005 (39); 2 = Hanson & Chen, 2007 (32); 3 = Van der Horst et al., 2007 (24); 4 = Pearson et al., 2009 (40); 5 = Pearson et al., 2008 (41) ; 6 = Taylor et al., 2005 (42); 7 = Woodruff & Hanning, 2008 (43).

  3. +, positive association; 0, no association; −, negative association; ?, mixed results.

  4. a, adolescents; c, children; e, total energy intake; f, fruit; fa, fat inake; j, juice; SES, socioeconomic status; sn, snacking; so, soft drink intake; v, vegetable.

Interpersonal     
 SESFamily income 4,5cfv,5av,3afa,3afvj,3asn,3ce,3cfa,3csn 5af
General SES2,65cfv,5av,3afa, 3asn,3csn 4,5af,3afvj
Parental/household education3afvj,4,5cfv,3ae,3afa,3cfvj3cfa5afv, 3asn, 3ce
Socioeconomic deprivation 3cfvj4 
Parental occupational status5af4,5av  
Hours worked by mother 5c,3cfvj 3csn
 Family compositionFamily size 5afv,3afa,3ce,3cfa  
Two parent family45fv,5av  
Male head of household   3afa
Residence with family   5af
Single-mother family 3afa 3ae
 Family cohesionFamily connectedness/cohesion3afvj,4,5afv   
 ModellingParental eating behaviour1,3cfvj,3a,4,5cf,5afv,7,3ae,3afa,3csn,3cfvj,3cfa5cv,3ce,  
Sibling intake3ae,3af,4   
 Peer influencePeer influences   1
 General parentingParental monitoring4   
 Food-related parentingControl over intake3cfa3cfvj,3ce3c,6 
Encouragement of intake3c,5cfv3cfvj3ce 
Child-feeding practices (authoritative, supportive)1,3afvj,   
Family food rules5cfv,75af 4
Pressure to eat 5cfv 3cfvj
Restriction of food choice 5cfv7 
Family facilitation of intake   5cfv
 AvailabilityHome availability of food, vegetables and juice1,5c,65afv3afvj3cfvj
Availability and accessibility breakfast items   4
Accessibility of food and vegetables3cfvj5c  
Availability of unhealthy foods 5af  
Availability of healthy foods7  5af
Food poverty  4 
 Family meal habitsFrequency of family breakfast5cf,3cfvj5afv,3afvj3cso5cv,3csn
Frequency of family diner 5cfv,5af,3aso,3afvj,3cfvj,3csn 3cso
Frequency of family meals5af,6,75av,3afvj 3aso
TV during meals 5c  
School     
 Meal locationMeals at home vs. school 3asn  
Lunch at other site than home or school  3asn 
Neighbourhood     
 SESArea deprivation index   3csn
Macro/societal     
 RegionNon-metropolitan residence   3ce,fa,
Geographic region   3ae,sn,
Degree of urbanization 3afa,  
City vs. county3afvj3aso  
 PriceFood price  6 
 MediaExposure to food advertising on TV  1,6,7 
Interpersonal level

Family cohesion (i.e. emotional bonding between family members), modelling and parental monitoring were positively associated with dietary behaviours across reviews, although the latter was only examined in one review. None of the interpersonal factors were negatively related to dietary behaviours. Family SES, family composition and family meal habits were unrelated to diet across reviews.

School level

No school-level factors yielded consistent findings.

Neighbourhood level

No neighbourhood-level factors showed consistent findings.

Societal or macro level

None of the macro-level factors were positively associated with dietary behaviours. Exposure to food advertising on TV was negatively related to healthy diets across reviews, as well as food price although the latter was examined in only one review.

Summary of consistent findings of for dietary behaviours in young people, based on strong reviews only

Below are consistent findings on correlates of dietary behaviours reported, based on reviews rated as strong quality only.

Positive

Family cohesion, modelling and parental monitoring were positively associated with dietary behaviours.

Negative

None of the factors was consistently negatively related to dietary behaviours.

Unrelated

SES, family composition and family meal habits were unrelated to dietary behaviours.

Differences between children and adolescents

Differences between children and adolescents in environmental influences on healthy eating could only be explored in three of the seven reviews (24,32,41). However, no clear differences emerged in environmental influences between children and adolescents.

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

The present review integrated findings from 18 published systematic reviews and meta-analyses that together synthesized findings from 671 unique studies regarding potential environmental influences on physical activity or dietary behaviours in children and adolescents. Despite the heterogeneity in measures, samples, specific behaviours or countries in the extensive body of research, the present review of reviews identified factors that are consistently related or unrelated to physical activity and dietary behaviours in young people. The consistency of results irrespective of heterogeneity suggests that these associations are more robust.

Physical activity in young people was found to be positively influenced by teacher SES, specific school types (e.g. more activity in public and high schools than private or vocational schools), facilities at school as well as in the neighbourhood for physical activity and traffic safety in the neighbourhood. Physical activity in young people was unrelated to modelling of friends and siblings, support of parents for physical activity, family size, home opportunities for physical activity, school support for physical activity, characteristics of neighbourhood residents, personal safety (e.g. neighbourhood hazards, concerns about crime) and exposure to sports media. Together these findings suggest that, physical activity is more consistently influenced by characteristics of the school and community environment than by features of the interpersonal environment. A likely explanation is that many physical activities occur outside the home environment (e.g. active transport, playing outdoors and sports classes in schools), thereby reducing the influence of the home environment. When schools and neighbourhoods facilitate physical activity, family and peer influences might not have additional effects. It might also well be that parents select specific schools and neighbourhoods to live in, so that family might have a more indirect relation with physical activity. Despite extensive research on the interpersonal environment, it appears to have no direct influence on physical activity. The school and neighbourhood environments may provide more promising avenues for future research and interventions.

In contrast to physical activity, factors at the interpersonal level play a pronounced role in young people's dietary behaviours, whereas none of the correlates at school, neighbourhood or societal levels are consistently related to dietary behaviours. Family cohesion, modelling and parental monitoring positively influence young people's dietary behaviours, but family SES, family composition and family meal habits were unrelated to dietary behaviours. These findings might indicate that healthy diets go hand in hand with having a positive family atmosphere, in which parents give the right example, have a good understanding of their children's lives and in which parents and children feel emotionally connected. Such a positive context might be more important than actual family composition, affluence or meal habits, which all are unrelated to dietary behaviours.

Generally, little is currently known of the role that macro-environmental factors (e.g. media, industry, marketing, policy) play in physical activity and dietary behaviours in young people. Studies on macro-level influences are largely lacking, whereas precisely these factors have the potential to impact on populations at large (20). An interesting exception is a cross-national study that found correlations between country-specific obesity prevalence rates and macro-environmental factors in the economic, physical and policy domain in 24 European countries (44). Given that this cross-national comparison focused on adults only, a similar approach might provide insight into macro-environmental influences on overweight in young people.

As noted before, only few factors were found to be consistently related or unrelated to physical activity and dietary behaviours in young people despite the extensive body of research. This illustrates that mapping these environmental influences is a complex affair, which at least in part could be attributed to methodological and theoretical challenges (45–47). A first challenge is on deciding how to measure specific environmental correlates. Assessments of environmental correlates may, for instance, reflect key statistics, data from geographical information systems or perceived environmental characteristics as rated by the target group (e.g. young people or their parents). The choice of assessment method has been shown to influence the associations between a specific correlate and weight-related behaviours (47–49). Also in the present review of reviews, we observed some different results according to the type of indicator that was used (see for instance Table 2). Notably, a negative association was found between crime incidence as derived from statistics and physical activity, whereas young people's concerns about crime appeared unrelated to physical activity. The distinction between objective and perceived indicators of aspects of the environment has important practical implications as perceptions about the environment are more amenable to change than the actual environment is.

A second complexity in documenting environmental influences on physical activity and dietary behaviours among youth pertains to the lack of understanding of causal mechanisms. The growing body of research regarding environmental correlates of weight-related behaviours largely consists of cross-sectional studies that aim to identify empirical associations, but these studies generally do not contribute to the conceptual understanding of causal mechanisms. Consequently, it remains unclear exactly how and why environmental factors exert their influence on weight-related behaviours. It is remarkable that within the abundance of studies of environmental influences on overweight, clear, conceptually sound hypotheses of the underlying process by which environmental factors impact on behaviour are lacking. Theoretical models are required that conceptualize the mechanisms that can link (combinations of) environmental factors to specific behaviours (50). Moreover, more insight is needed whether these mechanisms are similar across age, gender, ethnic background or SES. Not only does it need to be disentangled how and why environmental factors contribute to physical activity and dietary behaviours, but also for whom these processes are more or less likely. This might help to identify target groups for environmental interventions. In line with this point, it should be acknowledged that environmental factors do not influence physical activity or dietary behaviours in isolation. In the present review, we focused on whether or not specific environmental variables are directly associated with behaviour. However, it is very likely that individual and environmental influences interact and synergistically affect behaviours (51). Future research should explore how patterns of different internal and external factors exert their influence on behaviours.

Limitations

In the present paper, a systematic review of reviews is presented. Some limitations that are inherent in this procedure should be acknowledged. First of all, the findings do not refer to individual studies, but to aggregated findings across studies included in individual reviews. Methodological variation in individual studies may exist, that remain obscured in the present review. Systematic review of reviews generally cover a large number of individual articles (n = 671 in the present review of reviews). This makes it unfeasible to extract additional information about sample sizes, country of research or other characteristics from the individual articles that might be of interest. Data are extracted from reviews. A critical appraisal of reviews showed that reviews differed substantially in quality, which may have introduced a bias in our study (52). However, we took care in taking the quality of individual reviews into account and whether or not a quality assessment of studies had been performed was one of the quality criteria of the included reviews. A systematic review of reviews is a useful way of integrating findings when a large number of studies have been conducted and when individual reviews have focused on particular types of influences, on particular types of outcomes or on specific samples. The fact that only limited overlap existed between the studies included in the separate reviews provides a clear indication that these criteria are met in the domain of environmental influences on weight-related behaviours of young people. Reviewing reviews hence is a suitable method to more comprehensively identify environmental factors that do and do not influence weight-related behaviours of young people.

Conclusions and implications

This systematic review integrates findings from previous reviews that focused on environmental correlates of weight-related behaviours in young people. Many different environmental factors that are potentially linked to weight-related behaviours of young people have been studied, but only few consistent correlates of physical activity and dietary behaviours in young people were found. Policy and practice regarding the prevention of overweight of young people already address aspects of the obesogenic environment. An analysis of national policy documents on obesity prevention indicated that already in eight countries policies suggested the construction of safe walking and cycling paths, increasing safe and efficient public transport and reducing car use in order to promote physical activity (1). The present review appears to suggest that the role of these factors in physical activity is not yet fully understood. To date, not much evidence is available to support the efficacy of an environmental approach to obesity prevention (53,54). Notably, a meta-analysis of obesity prevention programs for children and adolescents showed that mandated improvements in diet (through direct manipulation of the food school environment) and in physical activity (through direct manipulation of physical education lessons) did not improve the efficacy of obesity prevention (54). Before effective environmental interventions can be developed and implemented, it is crucial to identify which environmental factors truly impact on physical activity and dietary behaviours and to carefully disentangle how these factors exert their influence on behaviours. Specific attention should be paid to exploring how individual, social and environmental interact so that optimal synergistic interventions could be developed.

Acknowledgement

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

This research is part of the TEMPEST project, supported by a grant from FP7, theme health (Grant Agreement No. 223488).

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  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information
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Supporting Information

  1. Top of page
  2. Summary
  3. Introduction
  4. Methods
  5. Results
  6. Discussion
  7. Conflict of Interest Statement
  8. Acknowledgement
  9. References
  10. Supporting Information

Table S1. Description of included reviews of environmental influences on physical activity among young people.

Table S2. Description of included reviews of environmental influences on dietary behaviours among young people.

FilenameFormatSizeDescription
OBR_784_sm_table_s1-2.pdf69KSupporting info item

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