The empirical evidence of a non-monotone relation between income and obesity is not well explained.We build a theoretical model combining income inequality and social comparisons to explain the link between income and obesity and study tax policy implications for fighting obesity. We assume that differences in food consumption patterns between poor and wealthy households partly reflect positionality, which is the concern for social status. Our key assumption is that positionality for low-calorie food consumption is positively related to a country's wealth. In this framework, body weight outcomes reflect competing income and positionality effects, yielding the following results. We explain the link between average obesity rates, and standards of living and suggest the existence of a Kuznets curve for obesity.For cross sections of the population, we explain the observed correlation between income and obesity, which is positive in poor countries, and negative rich countries. We find that increasing the relative cost of high-calorie food is less effective at decreasing the relative weight of poor individuals in rich countries than in poor countries.

This paper contributes to explaining the obesity epidemic and finding a potential remedy. We build a theoretical model of food consumption decisions that accounts for social influence. In our model, individuals’ rationality is affected by an endogenous social weight norm, which influences their calorie consciousness and perceived survival chances. Individuals are conformist, and the degree of conformism describes the extent to which individuals’ discounted utility is influenced by the social weight norm. With an endogenous social weight norm reflecting a heavier and heavier average body weight, we show that a high degree of conformism to the social norm could explain the obesity epidemic. In this environment, a government intervention decreasing energy density is ineffective at reducing steady-state body weight. This result could explain why this type of government dietary intervention seems to have had no effect on obesity, and suggests that the same type of intervention through the Food Stamps Program would be ineffective on its own. We also find that in the steady state, individuals can be overweight or underweight depending on their degree of conformism relative to the education they receive about the healthy weight. While education programs focusing on either diet or exercise have had moderate success, we show that focusing on healthy weight education could combat social influence and reduce obesity.

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Junk-food taxes have mixed effects on obesity and junk-food consumption. We build a theoretical model to explain empirical results and better understand how to address the obesity crisis. In our framework, hand-to-mouth consumers make an intertemporal choice between junk-food consumption and weight loss. Their choice depends on calorie consciousness, which is influenced by perceived after-tax relative prices and educational attainment. Thus, a junk-food tax modifies consumers’ intertemporal choice both through their budget constraint and calorie consciousness. As a result, the effect of the tax on body weight reflects competing income, intertemporal substitution, and calorie-consciousness effects. The model explains empirical observations such as the recent rise in obesity and differences in weight outcomes for different income levels. The model explains circumstances under which junk-food taxes can be effective or ineffective to reduce body weight as well as differences in elasticities of high-calorie food consumption for high- and low-income earners.

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