Heterogeneous effects of obesity on mental health: Evidence from Mexico.

Obesity can spread more easily if it is not perceived negatively. This issue may be more pronounced among the poor, a conjecture that we test in this paper. We start with general evidence on the concave relationship between income and obesity, both across countries and within Mexico, a country characterized by very unequal development levels and the highest obesity rate in the world. We suggest a general model that explains this stylized fact from a simple necessary condition, namely, the complementarity between nonfood consumption and health concerns. Then, we test the direct effect of overweight on mental health among Mexican women. We find a positive effect of obesity in the low consumption group and a depressing effect among the rich. This result is robust to the inclusion of a range of confounders (childhood conditions, lifestyle variables, food expenditure, and household shocks) and after instrumenting individual fatness by the variation in genetic predisposition. The complementarity between living standards and weight concerns may reflect different norms, different labor market penalties, or simply different returns to healthy time across the social spectrum.