Peer effects in adolescent overweight.

This study is the first to estimate peer effects for adolescent weight. We use data from the National Longitudinal Study of Adolescent Health (Add Health) and define peer groups using nominated friends within schools. Endogenous peer groups are accounted for using a combination of school fixed effects, instrumental variables, and alternative definitions of peers (i.e., grade-level peers). Mean peer weight is correlated with adolescent weight, even after controlling endogenous peer groups. The impact of peer weight is larger among females and adolescents with high body mass index. The results are consistent with social multipliers for adolescent overweight policies.