Could Obesity Be Contagious? Social Influence, Food Consumption Behavior, And Body Weight Outcomes

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.