The Thrifty Gene Hypothesis: Can It Explain the Obesity Epidemic?
In 1962, geneticist James Neel proposed the thrifty gene hypothesis, the idea that some of us are genetically doomed to get fat. During times of famine in our evolutionary past, our ancestors needed a mechanism to store excess calories to avoid starvation. Thus, we evolved an ability to store up calories in our fat tissue and hold onto those calories at all costs -- much as a squirrel gathers nuts in the fall in preparation for a cold hard winter.
Obesity researchers often invoke the thrifty gene hypothesis to try to explain why so many of us today are overweight and diabetic. The thinking goes like this. Our modern environment allows us access to a super abundance of calories. Human beings -- who evolved to live in times of famine -- are maladapted to this environment. We eat too much because the food is "there" for the eating.
This theory, which we'll dissect in depth later, is absolutely crucial to the Caloric Balance Hypothesis, the proposition that "calories count." Because without a thrifty gene hypothesis, Caloric Balance advocates have no coherent way to explain the obesity epidemic.
As we've discussed, the Caloric Balance Hypothesis tells us that obesity results from gluttony and/or sloth.
When you extrapolate from this logic, you must conclude that the obesity epidemic has resulted from an epidemic of sloth and gluttony in the population. After all, if sloth and gluttony cause individuals to get fat; then sloth and gluttony on a wider scale must cause populations to get fat.