The food retail environment surrounding Canadian schools and its impact on overweight and obesity

Abstract

Background: The prevalence of overweight and obesity in Canadian youth has increased considerably over the past few decades. In spite of considerable efforts, individual-level behavioural modification strategies have not been successful at preventing and treating obesity in youth. Research is emerging that has shifted attention to the environmental-level determinants of obesity. There is some evidence that the number and types of food retailers in a given neighbourhood may impact obesity risk in the individuals living in that neighbourhood, but little is known about the impact of the food retail environment on Canadian youth. Objectives: 1) To describe the food environment surrounding the school neighbourhoods of Canadian youth (grades 6 to 10), and, determine whether access to food retailers around schools differs by area-level SES. 2) To determine whether the number and type of food retailers surrounding schools is related to the overweight status of the students attending those schools. Each of these objectives was explored in a separate manuscript. Methods: A trend test was performed to determine if exposure to food retailers varied by neighbourhood socioeconomic status (SES) for 188 schools across Canada. Logistic regression was performed using a multilevel modeling approach to determine if an association existed between exposure to food retailers and overweight and obesity in the 7,281 school-aged youth attending the 188 schools, adjusting for individual- and area-level covariates. Types of food retailers considered included: full-service restaurants, fast food restaurants, sub/sandwich shops, donut/coffee shops, convenience stores, and grocery stores. Results: Objective 1. Nearly 75% of schools had at least one food retailer within 1 km of schools, and over 90% had at least one food retailer within 5 km. Exposure to the different types of food retailers within 1 km of schools did not vary significantly (p<0.05) across schools in low, moderate, and high SES neighbourhoods, with the exception of full-service restaurants. At the 5 km distance, the SES gradient was significant across all food retailer types, with low SES neighbourhoods exposed to the least number of food retailers. This effect disappeared when population density (number of retailers per 10,000 people) was considered, except for sub/sandwich shops and donut/coffee shops. Objective 2. Increased exposure to all six types of food retailers in the neighbourhoods surrounding schools was associated with a decreased likelihood of overweight and obesity. At the 1 km distance, the total number of food retailers had the strongest protective effect, while individual types of food retailers had a stronger effect at the 5 km distance. Conclusions: Objective 1. Most students in Canada have at least one food retailer within walking distance of their school. The food retail environment surrounding schools is not significantly impacted by the neighbourhood SES. Objective 2. Increased exposure to different types of food retailers in school neighbourhoods is associated with a decreased likelihood of overweight and obesity in Canadian youth. This suggests that having access to a large number and variety of food choices may facilitate healthy food choices and protect against the development of overweight and obesity.