Fast food costs and adolescent body mass index: evidence from panel data.

This study draws on four waves of the 1997 National Longitudinal Survey of Youth and external data to examine the relationship between adolescent body mass index (BMI) and fast food prices and fast food restaurant availability using panel data estimation methods to account for individual-level unobserved heterogeneity. Analyses also control for contextual factors including general food prices and the availability of full-service restaurants, supermarkets, grocery stores, convenience stores and commercial physical activity-related facilities. The longitudinal individual-level fixed effects results confirm cross-sectional findings that the price of fast food but not the availability of fast food restaurants has a statistically significant effect on teen BMI with an estimated price elasticity of -0.08. The results suggest that the cross-sectional model over-estimates the price of fast food BMI effect by about 25%. There is evidence that the weight of teens in low- to middle-socioeconomic status families is most sensitive to fast food prices.