To illustrate just how powerful the thrifty gene can be in helping to survive a famine, lets look to some studies done in the early 1950s in a strain of chronically obese mice. When these mice were allowed an unlimited food supply, they would balloon and add as much as half the body weight of normal mice. When these fat mice were deprived of food they survived an average of forty days while normal mice would only live for ten days at the most.
The basic underlying mechanism in the chronically obese mice and Pima Indians with the thrifty gene is a natural craving for carbohydrates that causes consumption of them whenever they are available, even if hunger is not present. They also possessed the ability to make more insulin and store the excess calories consumed as fat. Pima Indians with the thrifty genotype also easily develop resistance to insulin when they consume excess carbohydrates. What this additional mechanism produces is an even greater ability to store fat and as a result enables them to live through famines. With time, the survival of the fittest led to virtually an entire culture possessing the thrifty gene. Throughout the history of the world the ability to express the thrifty genotype was rewarded with survival. As a result, this genetic predisposition is one of the critical factors fueling the obesity epidemic.
Find out more about this book:Hunger Free Forever: The New Science of Appetite Control