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 why, ceteris paribus, poor persons are more prone to be severely overweight although eating is expensive and 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 citizen 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 loose weight demonstrate robustness of the basic mechanism and provide further interesting results.