Does outdoor advertising correlate with retail food purchases made by adolescents? A cross-sectional study in Canada.

Food marketing plays a substantial role in shaping adolescent diets, having wide-ranging ramifications for health behaviours and outcomes throughout the life course. Yet, there remains a dearth of research about how outdoor advertising as a specific channel of food marketing affects purchasing behaviours. We examine self-reported purchases made at retail food outlets by adolescents as it relates to the availability of outdoor food and beverage advertising around each participant's home, school, and along the journey to and from school. We also consider the impacts of sociodemographics and consumption attitudes on purchasing, as compared to the geographic availability of outdoor advertising. Data are drawn from a survey completed by 545 adolescents in 2018 across four secondary schools in the Middlesex-London region of Ontario, Canada. The availability of outdoor advertising in the home and school environment is marginally correlated with self-reported purchases made at fast food, table-based, grocery, and variety retail outlets. However, consumption attitudes, cultural background, and gender are significantly correlated with purchases, with substantially larger effect sizes. The overall results were consistent between estimating the availability of outdoor advertising in the immediate area surrounding the home and along the journey to and from school. There is considerable health promotion policy interest in regulating outdoor advertising around child-serving locations. However, scarce health promotion resources would be better allocated to educational programming that addresses the substantial role of consumption attitudes in affecting adolescent purchasing behaviour, as compared to the considerably weaker impact of outdoor food advertising observed in our analysis.