Estimating the Peer Effect on Youth Overweight and Inactivity Using an Intervention Study.

ABSTRACT BACKGROUND Understanding peer effect is potentially important for finding ways to combat the obesity epidemic. Nevertheless, it is not clear whether a peer effect exists because of the composition of the peer group, because the group members have similar, unobserved individual characteristics, or because of an endogenous effect. METHODS This issue is addressed here by using a unique longitudinal data set of 573 schoolchildren attending state schools in the Municipality of Aalborg, Denmark, during 2008-2010. To identify the spillover effect of a targeted intervention on peers, we use a difference-in-differences approach. RESULTS A targeted health intervention reduced body mass index (BMI) among overweight, inactive individuals and, more interestingly, that BMI among the nontreated peers was reduced by 1.04%. CONCLUSIONS The analysis suggests that individually targeted health intervention has a health benefit beyond the treated individual, which needs to be included when evaluating targeted policies aiming to combat childhood overweight and inactivity. [ABSTRACT FROM AUTHOR]