Is there a robust relationship between neighbourhood food environment and childhood obesity in the USA?

Objectives: To examine the robustness of the relationship between neighbourhood food environment and youth body mass index (BMI) percentile using alternative measures of food environment and model specifications. Study design: Observational study using individual-level longitudinal survey data of children in fifth and eighth grades merged with food outlet data based on student residential census tracts. Methods: The relationship between food environment and BMI was examined with two individual outcomes (BMI percentile in eighth grade and change in BMI percentile from fifth to eighth grade) and three alternative measures of food environment (per-capita counts of a particular outlet type, food environment indices, and indicators for specific combinations of outlet types). Results: No consistent evidence was found across measures (counts of a particular type of food outlet per population, food environment indices, and indicators for the presence of specific combinations of types of food stores) and outcomes to support the hypothesis that improved access to large supermarkets results in lower youth BMI; or that greater exposure to fast food restaurants, convenience stores and small food stores increases BMI. Conclusions: To the extent that there is an association between food environment and youth BMI, the existence of more types of food outlets in an area, including supermarkets, is associated with higher BMI.