Uncovering peer effects mechanisms with weight outcomes using spatial econometrics

• This paper applies spatial econometric methods to the study of peer effects and obesity.
• We distinguish between social multiplier effects and social norms effects using an augmented spatial autoregressive model.
• There are significant peer interactions in BMI, with the social norm effect being much larger than the social multiplier effect.
• These findings in the paper suggest that peer effects are important for overweight youth but not for obese youth.
• The peer influence for overweight adolescents appears to operate solely through social multiplier effect.

Research about how peers influence weight outcomes among adolescents has yielded mixed findings. This paper seeks to not only estimate these peer effects, but also to distinguish between two mechanisms: social multiplier effects and social norm effects. After estimating an augmented spatial autoregressive model using data from the National Longitudinal Study of Adolescent to Adult Health Survey, this study finds significant peer interactions in body mass index, which can be explained by both mechanisms of peer influence; the social norm effect is much larger than the social multiplier effect. The estimated peer effects for overweight and obesity statuses suggest that peer effects are important for overweight status but not for obesity status, and peer influence for overweight status appears to operate solely through social multiplier effect. These findings provide important information for the design of obesity-prevention interventions in schools.