The “Thrifty Gene” Theory
So, we understand a bit of why the U.S. Pimas have so much more obesity (and diabetes) than their Sierra Madre cousins- it’s large differences in activity levels, and perhaps, something to do with diet composition. That explanation still does not really explain why the U.S. Pimas are so overweight; shouldn’t the Pima brain appetite center make adjustments in appetite to compensate for the low activity level? The answer to the question is that maybe the appetite center should compensate, but it doesn’t. Many scientists who study obesity believe that over thousands of years, human genes have been selected that allow “overeating” when food is plentiful. This genetic trait would have important survival value in times of famine- all the lean and mean people would starve to death while those with excellent fat stores would be more likely to survive. This is the so-called “thrifty gene” theory. Whether this is true or not, it seems to make sense. It is also a very scary thought, since it may well be that in the twenty-first century (2001 and beyond), most people around the world do carry these thrifty genes and we don’t know how to make them go away. Maybe the Pimas’ dilemma is that they just have too much of what used to be a good thing?
Implications of the thrifty gene theory
If this thrifty gene business is true, we will need to either wait thousands of years until something happens to decrease fertility in people who carry these genes, or find other ways to deal with our misguided appetite centers (behavior modification, drugs, surgery, etc.) Maybe we should move to the Sierra Madre?
- Obesity: What We Can Learn From the Pima Indians
- Obesity: Activity Levels