The thrifty gene hypothesis is an idea developed by geneticist James Neel in 1962 to explain why people get fat. This theory suggests that neurocircuitry underlying food procurement and body fat storage evolved at a point in human history in which food was scarce as a means of promoting survival in times of famine.

Recent advances in technology have allowed for the creation and modification of foods, which artificially enhance palatability beyond what would be found in nature, especially in regards to sugar, fat, and caloric value. These calorie-rich, highly-palatable foods are abundant and easily accessible in the typical Western diet. This combination of factors may lead to the activation of reward-mediated neurocircuits, which evolved to reinforce feeding behavior, and desires to engage in pathologic overconsumption, which would have been advantageous in a time of famine but now, in a context of abundance, appear maladaptive. The thrifty gene hypothesis allows the “Caloric Balance” researchers to explain why only some of us get fat and not all of us. It also explains why it’s so difficult to lose weight. However, James Neel himself ultimately dismissed his thrifty gene hypothesis as likely not true. Instead, he came to blame obesity on the carbohydrates in our foods – specifically sugars and refined carbs.

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Kalhan SC, Prentice AM, Yajnik CS (eds). Emerging Societies - Coexistence of Childhood Malnutrition and Obesity: Obesity in Emerging Nations: Evolutionary Origins and the Impact of a Rapid Nutrition Transition. Nestlé Nutr Inst Workshop Ser Pediatr Program, vol 63, pp 47–57, Nestec Ltd., Vevey/S. Karger AG, Basel, © 2009.

Southam L, Soranzo N, Montgomery SB, Frayling TM, McCarthy MI, Barroso I, Zeggini E. Is the thrifty genotype hypothesis supported by evidence based on confirmed type 2 diabetes- and obesity-susceptibility variants? Diabetologia. 2009 Sep; 52(9), 1846-1851. Epub 2009 Jun 13.

Evolution of Obesity