Although there is no definitive explanation for the recent increase of obesity, the Thrifty Gene Hypothesis" provides some understanding of this phenomenon. In times when food was scarce, the ability to take advantage of rare periods of abundance and use such abundance by storing energy efficiently was undoubtedly an evolutionary advantage. Individuals with greater adipose reserves were more likely to survive famine. This tendency to store fat is likely maladaptive in a society with adequate and stable food supplies.

This theory has been suggested in the UK for the differing rates of obesity and subsequently, Type 2 diabetes, in numerous South Asian populations compared to the indigneous white population: Gujarati and in particular Bengali populations exhibit a greater prevalence of both.

Although many people likely have a genetic propensity towards obesity, in most cases this propensity requires the modern environment with increased caloric availability and decreased requirements for physical labor in order to be expressed fully.