The Obesity Code: Unlocking the Secrets of Weight Loss (Why Intermittent Fasting Is the Key to Controlling Your Weight)

by Jason Fung

THE FIRST ATTEMPT to explain the genetic basis of obesity was the thrifty-gene hypothesis, which became popular in the 1970s. This hypothesis assumes that all humans are evolutionarily predisposed to gain weight as a survival mechanism. The argument goes something like this: In Paleolithic times, food was scarce and difficult to obtain. Hunger is one of the most powerful and basic of human instincts. The thrifty gene compels us to eat as much as possible, and this genetic predisposition to gain weight had a survival advantage. Increasing the body’s food stores (fat) permitted longer survival during times of scarce or no food. Those who tended to burn the calories instead of storing them were selectively wiped out. However, the thrifty gene is ill adapted to the modern all-you-can-eat world, as it causes weight gain and obesity. But we are simply following our genetic urge to gain fat. Like a decomposing watermelon, this hypothesis seems quite reasonable on the surface. Cut a little deeper, and you find the rotten core. This theory has long ceased to be taken seriously. However, it is still mentioned in the media, and so its flaws bear some examination. The most obvious problem is that survival in the wild depends on not being either underweight or overweight. A fat animal is slower and less agile than its leaner brethren. Predators would preferentially eat the fatter prey over the harder-to-catch, lean prey. By the same token, fat predators would find it much more difficul...