Obesity is contagious! Evidence from US data

Obesity is a rising epidemic. This research study shows that the scale of such a phenomenon is due to the effects of peers on individual weight-related behaviour, as well as to the limits on dynamic behavior imposed by habits. We estimate a dynamic linear-in-means model to analyse the importance of social ties for US youth Body Mass Index. We show that imitation effects explain most of the variation in the Body Mass Index of individuals who were normal-weight and overweight during adolescence. Obese adolescents, instead, become future obese adults through wrong habits enforced by imitative behavior. These findings call for group-level policy interventions, as a social multiplier effect might take place.