People with low levels of patience have a greater chance of becoming obese, particularly at a time when meat and high-calorie foods are relatively inexpensive. These are the central findings of a new study by economists Charles Courtemanche, Garth Heutel and Patrick McAlvanah, published in the February 2015 issue of the Economic Journal.

They conclude that a tax on unhealthy food, though controversial, could be used to address the undesirable effects of impatience and over-consumption. Tackling the cost incentives of cheap, high-calorie snacks may make a significant impact for those who struggle with the problems of self-control that lead to obesity.

The study analyses data from the US National Longitudinal Survey of Youth (NLSY), focusing particularly on responses to survey questions about ''time preference''. This is a term economists use to describe how people make trade-offs between their present and future desires. In other words, it can quantify an individual''s level of patience.

The NLSY time-preference questions asked how much extra money the respondents would have to be offered to accept a yearlong delay in receiving a monetary reward of $1,000 – and then how much they would accept to wait for one month. These answers yielded patience measurements of the respondents, which can then be evaluated against measures of body mass index (BMI). The analysis shows that:

· Low patience corresponds with a susceptibility to obesity.

· Price incentives mix with impatience to influence BMI concentrations. The cheaper the food, the greater the gap between patient and impatient individuals on the BMI scale.

· US regions with greater reductions in food prices in recent decades show a larger percentage of obesity in impatient individuals. Regions with smaller reductions show a slightly smaller comparative gap between obesity in high-patience and impatient individuals.

· Even after controlling for well-known determinants of BMI, such as gender, race, education and income, impatience stands out as a major contributor to obesity.

· Impatient people respond more to growing cost incentives than patient people of any demographic.

· Impatient consumers are not just eating more food overall. A price change in fruits and vegetables has no bearing on high BMI. Data on food price trends throughout different US regions suggest that a drop in the price of meats or high-calorie foods can lead to greater BMI growth.

The authors note that BMI levels in the United States have grown over time, but the growth has not been uniform. Weight gains over the past several decades have been minimal for individuals at the lower end of the BMI spectrum, but substantial for those at the higher end. As a result, the percentage of people with a BMI over 30 – indicating obesity – has skyrocketed. The study looks at who has been consuming more and what traits cause unhealthy BMI growth.

Co-author Charles Courtemanche comments on the findings:

''BMI has remained stable for much of the US population, but there is a problem for one subsection of the population, who are gaining dangerous levels of weight.

''People with a predisposition for impatience are affected by the short-term availability of cheap food, leading to an upsurge in obesity for this part of the population. Essentially, cost incentives interact with impatience to cause weight gain on a large scale.

''Greater knowledge of how obesity levels increase could open doors for discussion on various policy responses and help target the root of the epidemic.''


''Impatience, Incentives and Obesity'' by Charles Courtemanche, Garth Heutel and Patrick McAlvanah is published in the February 2015 issue of the Economic Journal. Charles Courtemanche and Garth Heutel are at Georgia State University. Patrick McAlvanah is at the Federal Trade Commission.