A mass phenomenon: the social evolution of obesity.

This paper proposes a theory for the social evolution of obesity. It considers a society in which individuals experience utility from consumption of food and non-food, the state of their health, and the evaluation of their appearance by others. The theory explains under which conditions poor persons are more prone to be overweight although eating is expensive and it shows how obesity occurs as a social phenomenon such that body mass continues to rise long after the initial cause (e.g. a lower price of food) is gone. The paper investigates the determinants of a steady state at which the median person is overweight and how an originally lean society arrives at such a steady state. Extensions of the theory towards dietary choice and the possibility to exercise in order to lose weight demonstrate robustness of the basic mechanism and provide further interesting results.