Title:
The proportion of excessive fast-food consumption attributable to the neighbourhood food environment among youth living within 1 km of their school.

Abstract:
The study objective was to estimate the proportion of excessive fast-food consumption by youth that is attributable to living and attending school in a neighbourhood with a moderate or high density of fast-food restaurants. This was a cross-sectional study of 6099 Canadian youths (aged 11-15 years) from 255 school neighbourhoods. All participants lived within 1 km of their school. The density of chain fast-food restaurants within a 1-km circular buffer surrounding each school was determined using geographic information systems. Excessive fast-food consumption (≥2 times per week) was assessed by questionnaire. Multilevel logistic regression analysis was used to examine associations. The population attributable risk estimates of excessive fast-food consumption due to neighbourhood exposure to fast-food restaurants were determined based on the prevalence of exposure and the results from the logistic regression. Eight percent of participants were excessive fast-food consumers. After adjusting for sociodemographic factors (i.e., gender, race, and socioeconomic status), it was found that youths from neighbourhoods with a moderate (odds ratio (OR), 1.68; 95% confidence interval (CI), 1.11-2.54) or high (OR 1.70; 95% CI 1.12-2.56) density of chain fast-food restaurants were more likely to be excessive fast-food consumers than were youths from neighbourhoods with no chain fast-food restaurants. Approximately 31% of excessive consumption was attributable to living in neighbourhoods with a moderate or high density of fast-food restaurants. Thus, the fast-food retail environment within which youth live and go to school is an important contributor to their eating behaviours.