Conspicuous leisure, time allocation, and obesity Kuznets curves

We build a theoretical model to explain the complex patterns of income and obesity, accounting for changes in behavior related to exercise. We combine the theory of time allocation with the theory of conspicuous leisure in a growth model, assuming that consumption expenditures connected to exercise time are conspicuous, and that conspicuous behavior changes with economic development. As a result, as economies develop, we show that there is a growing wedge between optimal exercise and consumption choices made by individuals with different income levels. We show that this pattern is connected to a dynamic Kuznets curve linking body weight to economic development over time, and a static Kuznets curve linking different steady state levels of income per worker to body weight. Thus, our model helps explain the rise and slowdown in obesity prevalence in the USA, as well as the positive correlation between obesity and income per worker in developing countries, and the negative correlation between obesity and income per worker in industrialized countries. We supplement our theoretical results with numerical simulations of the static and dynamic obesity Kuznets curves for the USA. We show that while exercise choices have contributed to a slowdown in the rise in obesity prevalence, there is to this date no dynamic Kuznets curve pattern for obesity in the USA. By contrast, we find the existence of a static Kuznets curve: the steady state level of average body weight increases with the per worker stock of capital up to a level of 186.5 pounds, corresponding to a capital stock 25% higher than the current steady state US capital stock, and decreases thereafter. We discuss policy implications of our findings.