What is the effect of commercial food and non-alcoholic beverage marketing on the dietary intake of children and adolescents? Protocol for systematic review and meta-analysis with an equity lens.

BACKGROUND: Previous reviews have shown that food and beverage marketing increases dietary intake among children. However, no updated review has been conducted since the COVID-19 pandemic. Furthermore, limited evidence exists on how this effect varies by sociodemographic factors and marketing media. The proposed study aims to assess and quantify the effect of food and beverage marketing exposure on children's dietary intake and to examine variations based on age, sex, ethnicity, socioeconomic position, and marketing medium. METHODS: A systematic review of peer-reviewed primary studies will be conducted by including studies on dietary intake from two previous reviews conducted for the World Health Organization (WHO) from 1970 to March 2020, and by searching 19 databases from April 2020 to October 2024. The literature search will be supplemented with backward citation searching of retrieved reviews and included studies. The search terms will encompass three key concepts: food- and beverage-related marketing, dietary intake, and population. Eligible studies must assess the impact of advertising on dietary intake. Two independent reviewers will conduct literature review, data extraction, and quality assessment, with discrepancies resolved by consensus with a third reviewer. Data will be extracted into a standardized evidence table and, where appropriate, included in a meta-analysis to synthesize quantitative findings. Risk of bias will be assessed using the Risk of Bias 2 tool for randomized controlled trials and the Newcastle-Ottawa Scale for non-randomized studies. Publication bias will be examined using funnel plots and trim-and-fill methods, while heterogeneity will be assessed with the I2 statistic. The overall quality of evidence will be evaluated using the GRADE approach. DISCUSSION: This review will be the first comprehensive assessment of the effect of food and beverage marketing exposure on children's dietary intake, encompassing studies from 1970 to 2024. It will also assess the potential heterogeneity of effects by sociodemographic groups and marketing media. The findings will inform evidence-based policies aimed at reducing marketing-driven dietary risks among children. Limitations include reliance on previous WHO-commissioned reviews for studies published before April 2020, which may introduce selection bias, and a focus on acute exposure, potentially limiting applicability to real-world, long-term effects. SYSTEMATIC REVIEW REGISTRATION: PROSPERO CRD42025641870.