Humans need food (and love) to survive. At the evolutionary level, the survival of biological species is mediated by growth, fertility and longevity phenotypes. However, the human race has evolved in an environment of extremely difficult periods of time, when food was scarce. Hence, the act of hunting or gathering food was laborious and required higher energy expenditure than what it takes to have food nowadays. Such a scenario promoted the ability to eat as much as was available. The "thrifty" genes may thus evolved to promote human survival in a life of famine-to-feast cycle. The scenario, especially in the economically advanced countries, has been changed in the last two decades: the average person has enough money to fill the daily caloric needs with fast-food meals. And the average daily energy expenditure has declined in parallel with a sedentary lifestyle. Hence the evolutionary pattern of "the more you eat, the better for survival" became no longer an advantage but a liability, and the presence of Homo obesus is increasing dramatically.
Biomedical Reviews 2006; 17: v-vi.
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