Effect of large-scale social interactions on body weight.

I estimate models of endogenous social interactions in body weight at the county and state levels. The results show that dispersion in body weight across time and space in the U.S. is not clearly excessive, and that much of this variation can be attributed to observable individual and regional characteristics. Models exploiting variants of methods proposed by Glaeser et al. (2003), fixed effects, instrumental variable and split-sample instrumental variable methods to address endogeneity suggest that there are not large social multipliers on body weight outcomes. The evidence suggests there may be small multipliers on BMI, obesity, and morbid obesity. There is no evidence that underweight is subject to a social multiplier. The results are sensitive to specification.