The impact on dietary outcomes of licensed and brand equity characters in marketing unhealthy foods to children: A systematic review and meta‐analysis

Summary Licensed and brand equity characters are used to target children in the marketing of products high in fat, salt, and sugar (HFSS), but the impact of characters on dietary outcomes is unclear. The primary aim of this review was to quantify the impact of both licensed and brand equity characters on children's dietary outcomes given that existing regulations often differentiates between these character types. We systematically searched eight interdisciplinary databases and included studies from 2009 onwards until August 2021, including all countries and languages. Participants were children under 16 years, exposure was marketing for HFSS product with a character, and the outcomes were dietary consumption, preference, or purchasing behaviors of HFSS products. Data allowed for meta‐analysis of taste preferences. A total of 16 articles (including 20 studies) met the inclusion criteria, of which five were included in the meta‐analysis. Under experimental conditions, the use of characters on HFSS packaging compared with HFSS packaging with no character was found to result in significantly higher taste preference for HFSS products (standardized mean difference on a 5‐point scale 0.273; p < 0.001). Narrative findings supported this, with studies reporting impact of both character types on product preferences including food liking and snack choice. There was limited evidence on the impact on purchase behaviors and consumption. These findings are supportive of policies that limit the exposure of HFSS food marketing using characters to children.


| INTRODUCTION
Children are exposed and targeted by a multitude of food and drinks marketing, the majority for products high in fat, salt, and sugar (HFSS). [1][2][3][4] Marketing increases short-term consumption, preference for, and purchase intention of HFSS products by children. [5][6][7] The impact on consumption can accumulate, as small excesses in daily energy intake can contribute to overweight and obesity over time. 8 Marketing of HFSS food and drinks is high on the public health and policy agenda; the use of characters in marketing has been identified as a persuasive technique by the World Health Organization (WHO)-UNICEF-Lancet Commission. 9 Marketing includes any form of commercial communication that acts to advertise or promote a product or service. 10 It occurs across a plethora of mediums, including television (TV), films, radio, magazines, digital mediums (social media platforms, websites, apps, streaming services, advergames, and text/email), physical mediums (billboards, point-of-purchase displays), and sport sponsorship. WHO has recommended reducing the marketing of HFSS/unhealthy foods and nonalcoholic beverages to children, but this is complex due to the variety of mediums across which marketing occurs. 10 The importance of including both brand equity and licensed characters within restrictions is specifically stated by the WHO, 11 as advertising restrictions commonly differentiate between licensed characters (borrowed with no brand association, e.g., Disney characters) and brand equity characters (created by the brand, e.g., Coco the Monkey). Several countries include the use of characters in their restrictions (e.g., the United Kingdom, Ireland, Australia, Chile, and Portugal), but this commonly only applies to licensed characters. [12][13][14][15] Brand equity characters are often exempt from HFSS marketing restrictions (e.g., the United Kingdom, Ireland, and the voluntary EU pledge from leading food and beverage companies) and are allowed to "sell the products they were designed to sell." 14,16 Despite the WHO recommending that packaging be considered a form of marketing, it is not included in restrictions in most countries. [12][13][14][15] Restrictions also commonly apply only to predigital media and therefore need to be updated in line with the shift to digital marketing. 14,17 In 2020, nearly all children in the United Kingdom aged 5-15 went online, and over half use social media apps/sites. 18 Chile is an exception, where comprehensive policies exist that ban the use of characters across all HFSS product marketing. 19 Content analyses and systematic reviews of marketing practices reveal characters as one of the most commonly used tactics for promoting food and drinks, disproportionately HFSS products, to children on packaging 20,21 and TV. 22,23 There is some evidence that licensed and brand equity characters increase children's food preference, choices, intake, and purchasing behaviors in relation to HFSS products. 6,24,25 However, there are limitations in the current reviews; one did not provide the search strategy and therefore was not replicable, 24 a lack of focus on characters, 6,25 and effects not being quantified through metaanalysis. Therefore, the current literature does not provide information on the specific impact of characters on child dietary outcomes.
We undertook a systematic review to synthesize the most upto-date evidence on how characters used in marketing, specifically advertising and packaging, impact a range of children's diet-related outcomes. We aimed to extend previous work by quantifying the effects of characters in marketing on children's purchasing behaviors and intentions; children's food preference and objectively measured food consumption (e.g., energy intake/quantity of items consumed); and examining whether character type influenced the response. We also sought to assess if child characteristics (e.g., age, socioeconomic status [SES]) or marketing format (content within advertisements vs. on packaging) impacted responses. This work is of particular relevance for informing policy makers and in formulating evidence-based advertising regulations.

| Protocol and registration
The current systematic review was registered with PROSPERO (registration number: CRD42019153853) and conducted and reported using the PRISMA checklist. 26

| Eligibility criteria, information resources, and search strategy
Quantitative peer-reviewed articles/studies (experimental with appropriate comparison group or nonexperimental "real world") were eligible for inclusion; population criteria were children and adolescents (aged between 0 and 16 years, in line with UK advertising regulation definition of children); all geography, languages, and studies between 2009 and August 2021 were included; intervention criteria were any form of HFSS food advertisement featuring a character (i.e., TV, packaging, and advergames); and outcomes were HFSS food consumption (objectively measured, that is, ad libitum consumption), food preferences (i.e., self-reported and like/dislike ratings), and food purchasing behavior or intention (i.e., quantity of product purchased and intention to purchase or to ask/pester parent to purchase). Studies from 2009 onwards were included to ensure results were most relevant to current marketing strategies and advertising practices. Exclusion criteria were participant age (over 16 years), date of publication (pre-2009), design (content analysis, reviews, and qualitative or nonpeer review, e.g., dissertations), intervention (no HFSS advertisement exposure with a character), and outcome measure (no measure of food choice, consumption, intake, purchase, and purchase/pester intention).  Table S1 for details of search and Table S2 for search history). Search results were firstly imported into EndNoteX9 to remove duplicates and then into EPPI-Reviewer 4, which was used for screening and to manage the search.

| Study selection
Articles were double screened on title and abstract and then full text, with discrepancies jointly reconciled. Full-text articles were acquired through web and online library services; all papers eligible for full-text screening were retrieved successfully.

| Data extraction and items
Data from included studies were independently doubly extracted.
Additional data from six studies for meta-analyses were requested from corresponding authors, of whom three responded with the required data.
Data extraction included study identification (authors, country, and year of publication), target population (children and/or adolescents), sample group description (size of sample, age range, and mean age of participants), study description (study design and assignment to conditions), intervention description (advertising medium and brand character), comparison type (HFSS food advertisement vs. healthy food or nonfood advertisement), test foods used, outcome type (consumption, preference, or purchasing), and outcome measures (kcal, kJ, grams, preference ratings, and purchase request measures).

| Assessment of quality
The Cochrane Risk of Bias Tool (RoB 2) 27 was used to assess included experimental studies for bias. This was undertaken doubly and independently, with discrepancies jointly reconciled.

| Data synthesis
We completed descriptive synthesis of studies first and then explored potential for meta-analysis. To be included in meta-analysis, experimental studies were required to have an exposure of HFSS marketing that featured a character and a suitable comparison group, including HFSS marketing with no character, or healthy/nonfood marketing with or without a character. Due to the differences in the design (between-subjects and within-subjects), HFSS food product (cereal, crisps, etc.), and packaging exposure, a DerSimonian-Laird randomeffects model was used. We graphically presented the results using forest plots. Analyses were conducted using Stata (16.1, StataCorp LLC, College Station, TX). 28 Subgroup analysis by character type was conducted, assessing the differential effects of licensed characters to brand equity characters. Sensitivity analysis was conducted by omitting studies assessed to have a high risk of bias, to test the stability of the results. Heterogeneity of studies was tested using the I 2 statistic, with a score >50 indicating presence of heterogeneity. 29 Publication bias was assessed using Egger's test, funnel plot, and trim-and-fill analysis. 30,31 3 | RESULTS

| Study selection
The database searches yielded 2352 articles, resulting in 1682 after removing duplicates. Following title and abstract screening, 1557 articles were excluded, and 125 were included to be screened on full text. This led to the final inclusion of 16 articles (20 studies), with five studies included in meta-analysis ( Figure 1). There were 109 articles excluded after screening on full text: 66 due to lacking an exposure that met all inclusion criteria (a HFSS product marketing that explicitly included a character), 21 did not have the outcome of interest, and 18 lacked a control or appropriate comparison group.

| Study description and results
A summary of study information is provided in Table 1 including details on participants, setting, design, intervention, outcomes assessed, and findings.

| Description of studies
The age of participants ranged from 2 to 15 years old; for the five studies included for meta-analysis, participants' ages ranged from 4 to 11.5 years (mean = 6.5 years). The majority of studies were conducted in the United States (n = 11), followed by the United Kingdom (n = 2), India (n = 1), Australia (n = 1), Austria (n = 1), Belgium (n = 1), Guatemala (n = 1), Spain (n = 1), and Uruguay (n = 1). Studies tended to be experimental with a mixture of between-subject and withinsubject designs, and most were conducted in schools (n = 9). The most common HFSS exposure was packaging with a character (n = 12), followed by advergames (n = 4), print adverts (n = 2), TV adverts (n = 1), or film product placement (n = 1). The featured characters included licensed (n = 12; including Dora the Explore and Scooby-Doo), brand equity (n = 5; including Coco the Monkey and Pom-Bear), or both (n = 3). HFSS products were a mix of familiar branded (e.g., Pom-Bear Potato Snacks and Oreos), unfamiliar branded (i.e., only available in another country, Honey O's), fictitious brand (i.e., created for the experiment, Snackcookies and Sugarbits) or unbranded (i.e., shown in clear or no packaging; crisps and donuts). Outcomes, related to the marketed HFSS product, were preference (n = 17, including taste rating), purchasing behaviors (n = 3, including intention to purchase), and consumption (n = 5, including ad libitum intake).

| Preference outcomes
The use of characters had a significant impact on HFSS product preference across most studies. Ten studies showed that the marketing of HFSS products with characters led to significantly higher preferences (including taste rating, 44,45 food liking, 32 forced pair product choice, 32,35,39,42,45 and snack choice [38][39][40]45 ) for the marketed HFSS products compared with the control conditions (no character with the same HFSS marketing or nonfood exposure). Of the other three studies, one compared characters in an HFSS advergame to a healthy advergame with character and a nonfood advergame with no character, with no significant differences found in forced snack choice between the three advergame conditions. 43 A further study compared an HFSS advergame with a control condition and found children in the advergame condition chose the advertised snack choice more frequently than control, but this was not significant. 46 Conversely, one study found that packaging without characters was chosen significantly more compared with packaging with licensed characters in a forced choice task. 41

| Meta-analysis of studies examining taste preference
Five studies provided sufficient data to be included in meta-analysis of taste preference, three licensed and two brand equity. 36,37,39 Taste preference or food liking (combined taste preference and food wanting) was measured on 5-point smiley face Likert scales (1, low preference; 5, high preference), so standardized mean difference (SMD) was used. Further details of the outcome measures and the comparison groups are included in Table S3. The results from the meta-analysis show that the use of a character in HFSS product packaging, compared with HFSS product packaging with no characters, resulted in a significantly higher taste preference for HFSS products with a pooled effect size of 0.273 (95% CI 0.123, 0.423; p < 0.001; I 2 = 9.5%; Egger's regression analysis showed no evidence of publication bias (p = 0.700), and trim-and-fill analysis suggested potential evidence of one missing study (see Figure S4). A sensitivity analysis was conducted, omitting the high risk of bias study, 38 and was not found to impact the results (see Figure S5).

| Purchase intentions
The use of characters had a significant impact on purchasing behaviors, with two studies finding evidence suggesting that the use of characters in HFSS marketing led to higher levels of intended requests or baseline for printed advert. 47 One study found that there was no significant difference in purchase intentions for HFSS product between exposure to print advert with licensed character to noendorsement exposure. 34

| Consumption outcomes
Five studies measured consumption outcomes and found mixed evidence. Two studies found use of characters had a significant impact on consumption outcomes, with significantly higher ad libitum consumption of marketed HFSS products in an HFSS advergame condition compared with a healthy food advergame 33 ; and intended consumption frequency of the marketed HFSS food was significantly higher following exposure to character endorsement compared with baseline, for both licensed and brand equity characters. 47 Two studies showed no significant difference between conditions with and without licensed characters, on HFSS packaging 38 or advergame, 46 and results were unclear in another study. 35 3.8 | Impact of age Evidence was mixed regarding how age influenced preference and consumption outcomes. Fifteen studies reported the impact of age; 10 found it was not a significant factor (including one consumption study), 3,33,[38][39][40]42,45,46 one reported a directional effect/trend with age, 38 one reported a trend for younger participants to be impacted more for preference outcomes, 32 and three found that younger age significantly impacted preference outcomes (across 5-10, 6-9, and 4-6 age range, respectively). 37,41,44

| Other secondary outcomes
Three studies reported the impact of SES, and all found that SES had no impact on taste rating outcomes, but meta-analysis by SES was not possible. 3,39 No studies reported whether advert format (e.g., TV advert vs. advergame) influenced outcomes or examined long-term effects. Effect of character type was directly assessed in two studies; licensed characters resulted in significantly greater consumption and intended purchase requests 47 and product preference, 35 compared with brand equity characters.

| Impact of country
Because a large proportion of studies were conducted in the United States (n = 11), the impact of country of origin for studies on general findings was considered. There was no difference in the results by country of study, with 7 out of 9 non-US studies and 9 out of 11 US studies finding similar things.
F I G U R E 2 Forest plot showing standardized mean difference in taste preference of HFSS products between HFSS packaging with and without a character HFSS advert, by character type

| Quality of studies
The risk of bias was assessed as mostly low, with three studies assessed as having some concerns and four studies, from the same article, assessed as high risk (see Figure S6 for bias assessment). The studies that were assessed as having some concerns were due to concerns with the randomization process 47 or selection of reported result. 36 The studies included in meta-analysis were assessed as mostly low risk and sensitivity analysis was conducted to assess results when high-risk study was omitted (see Figure S5).

| DISCUSSION
Our extensive systematic review included the first meta-analysis examining the impact of characters used in the marketing of HFSS products to children and found consistent evidence that marketing HFSS foods with characters influences children's preferences.
We found consistent evidence that HFSS packaging using both licensed and brand equity characters resulted in children having significantly higher preferences for an advertised product, compared with no character. The meta-analysis results showed that the presence of a character resulted in a significantly higher taste preference for HFSS products, compared with packaging with no characters. The SMD of 0.27 indicates a relatively small effect 48 ; however, small effects can accrue to create meaningful change at a population level. 49 Characters appeared to positively impact purchase intentions, but evidence was more limited, and the evidence for consumption outcomes was mixed.
We found limited evidence that age and SES influenced the impact of advertising. There was some evidence of greater impact among younger compared with older children but no evidence of differences by sociodemographic circumstance. A recent review found consistent evidence from a large number of studies that children from lower SES and ethnic minority backgrounds are exposed to a greater amount of advertising for unhealthy products compared with less disadvantaged and nonethnic minority children. 50 This suggests that, regardless of impact from a single advert exposure, children from minority and disadvantaged backgrounds are likely to be disproportionately affected by advertising and highlights the role of greater regulation in addressing health inequalities.
Our findings provide evidence that the use of characters, in particular brand equity characters, are effective marketing tactics that impact diet-related outcomes in children. This is important to consider when developing policies aiming to reduce the impact of marketing on children's health. Children are uniquely susceptible to the effects of advertising, particularly because they are not cognitively mature and may not fully understand the intent of advertising. 51 Characters are an influential tool in marketing as they appear to attract the attention and gain the trust of children, leading to increased brand recognition, positive brand attitudes, and brand loyalty. 52 This is especially true for established characters, with whom children may form parasocial relationships (single-sided connections between media users and on-screen characters). 53 This connection is exploited in marketing through evaluative conditioning, where positive feelings towards licensed or well-known brand equity characters are used to transfer positive feelings to the marketed product. 54,55 This effect is used advantageously by brands through cross-promotion, whereby licensed characters from popular children's media are utilized in HFSS marketing, and subsequent exposure to these characters in their original media (e.g., seeing licensed characters in movies and TV shows). This cross-promotion creates additional marketing outside advertising contexts and beyond regulation. 52,56,57 This suggests that the effects of using characters in marketing may be underestimated.
Characters are used extensively to market HFSS products to children. 20 and 9 p.m.) on TV and on demand program services, and a restriction on paid-for-less healthy food and drink advertising online, has been announced by the UK Government, 58 which could overcome some of the gaps in regulation and lower exposure to character-based HFSS advertising. The extension of broadcast regulations to cover product packaging has also been recommended, 21 as the use of characters on packaging that targets children is unrestricted in the United Kingdom and elsewhere 13,14 and is pervasive on HFSS products. 21 The impact of characters packaging on dietary outcomes is evidenced in our meta-analysis and wider review. Some companies have voluntarily committed to limit the use of characters on packaging for some of their products, including cereal boxes at Lidl 59 and products that do not meet specified thresholds at Unilever. 60 This shows some awareness and recognition of the power of this marketing approach from the food and beverage industry, although self-regulation of industry has typically not been effective and adherence to voluntary codes may not sufficiently reduce exposure. 61,62 Independent third party monitoring, with clearly defined and rigorous consequences, was recommended in a recent study on compliance and effectiveness of industry self-regulation of HFSS food TV advertisement to children. 63 Regulation and compliance across all potential marketing mediums is complex and challenging, but comprehensive restrictions and enforcement are likely to be necessary to effectively reduce children's exposure to marketing for HFSS foods.

| Limitations
Our review has some limitations; only five studies were eligible for meta-analysis, and the samples for character subgroup analysis were small; therefore, care due to variability needs to be taken. Although most were of reasonable quality with low/some concerns of bias, one study was deemed as high risk of bias as it was not randomized. Heterogeneity was low, and a random-effects model was used to account for differences in the advertising exposures. The criteria of only including papers from 2009 onwards restricted the results to some extent but ensured that the findings were reflective of contemporary marketing practices and relevant to inform the thinking of policy makers. Due to a lack of studies measuring consumption and purchase behaviors, with appropriate comparisons, meta-analysis was only possible for preference outcomes; five studies (from four articles) were included in meta-analysis. A limitation to our secondary aim to explore outcomes by SES was that only three studies provided appropriate data or examined the impact of SES. A further limitation is that all included studies were experimental, despite inclusion criteria including real-world studies; therefore, there would be various assumptions involved in extrapolating these findings to broader populations.
Further primary research, especially for digital marketing and on social media platforms, would be useful in further developing the evidence base.

| Conclusion
Our data provide further evidence that HFSS marketing using characters increases preference for HFSS products compared with not using characters and suggests purchasing behaviors and consumption are also deleteriously impacted. These findings suggest that reduced exposure of children to HFSS marketing including all character types and including packaging may have beneficial impacts upon dietary taste preferences and choices.