Recent obesity trends in children and adolescents suggest a plateau. However, it is unclear whether such trends have been experienced across socioeconomic groups. We analysed whether recent trends in child and adolescent overweight and obesity differ by socioeconomic position (SEP) across economically advanced countries. Eligible studies reported overweight and obesity prevalence in children and/or adolescents (2-18 years), for at least two time points since 1990, stratified by SEP. Socioeconomic differences in trends in child and adolescent overweight and obesity over time were analysed. Differences in trends between SEP groups were observed across a majority of studies. Over half the studies indicated increasing prevalence among low SEP children and adolescents compared to a third of studies among children and adolescents with a high SEP. Around half the studies indicated widening socioeconomic inequalities in overweight and obesity. Since 2000 a majority of studies demonstrated no change or a decrease in prevalence among both high and low SEP groups. However around 40% of studies indicated widening of socioeconomic inequalities post-2000. While our study provides grounds for optimism, socioeconomic inequalities in overweight and obesity continue to widen. These findings highlight the need for greater consideration of different population groups when implementing obesity interventions.

Actions to improve population diets should mitigate the barriers to healthy eating to create environments that support healthy eating across the socioeconomic gradient. Systematic Review Registration: PROSPERO registration number CRD42017065243.

Summary Children's exposure to advertising of unhealthy food and nonalcoholic beverages that are high in saturated fats, salt and/or sugar is extensive and increases children's preferences for, and intake of, targeted products. This systematic review examines the differential potential exposure and impact of unhealthy food advertising to children according to socio‐economic position (SEP) and/or ethnicity. Nine databases (health, business, marketing) and grey literature were searched in November 2019 using terms relating to ‘food or drink’, ‘advertising’ and ‘socioeconomic position or ethnicity’. Studies published since 2007 were included. Article screening and data extraction were conducted by two independent reviewers. Quality of studies was assessed using the Newcastle‐Ottawa quality scale. Of the 25 articles included, 14 focused on exposure to unhealthy food advertising via television, nine via outdoor mediums and two via multiple mediums. Most studies (n = 19) revealed a higher potential exposure or a greater potential impact of unhealthy food advertising among ethnic minority or lower SEP children. Few studies reported no difference (n = 3) or mixed findings (n = 3). Children from minority and socio‐economically disadvantaged backgrounds are disproportionately exposed to unhealthy food advertising. Regulations to restrict unhealthy food advertising to children should be implemented to improve children's diets and reduce inequities in dietary intake.