Widespread obesity in the U.S. is a relatively recent phenomenon, reaching epidemic proportions only in the last 15 years. However, existing research shows that while calorie expenditure through physical activity has not changed appreciably since 1980, calorie consumption has risen dramatically. Consequently, any explanation of obesity must address the reason why consumers tend to overeat in spite of somewhat obvious future health implications. This study tests for an addiction to food nutrients as a potential explanation for the obesity epidemic. Specifically, we use a random coefficients (mixed) logit model applied to household scanner data to test a multivariate version of the rational addiction model of Becker and Murphy and Chaloupka. We find evidence of a rational addiction to all nutrients – protein, fat and carbohydrates – as well as to sodium, but particularly strong evidence of a forward-looking addiction to carbohydrates. The implication of this finding is that price-based policies – sin taxes or produce subsidies that change the expected future costs and benefits of consuming carbohydrate-intensive foods – may be effective in controlling excessive nutrient intake.

Native American obesity and the associated health conditions are generally thought to result in part from a genetic predisposition to overeating fats and carbohydrates, called the “thrifty gene.” Although coined by nutritional scientists, this study maintains the origin of the thrifty gene lies in economics. Apparently harmful overconsumption and addiction constitute economically rational behavior if the increment to current utility from adding to one’s stock of “consumption capital” is greater than the present value of utility lost in the future due to ill health and the costs of withdrawal. Tests of these conditions for such “rational addiction” are conducted using two-stage household production approach. The results obtained by estimating this model in a panel of Native and non-Native supermarket scanner data show that both Natives and non-Natives tend to be inherently forward-looking in their nutrient choices, but Natives tend to have far higher long-run demand elasticities for carbohydrates compared to non-Natives. Consequently, reductions in real food prices over time, primarily among foods that are dense in simple carbohydrates, leads Native Americans to over-consume potentially harmful nutrients relative to their traditional diet.