If that is so, perhaps you could tell me why it is that an examination of hundreds of thousands of photos taken from the dawn of photography to the present age show that the Americans of the past--middle-class or upper-class Americans who did not have to do hard physical labor--were not fat? If heredity helped to determine weight, then our ancestors should have been obese as we are today. Perhaps also you could explain why it is that, while modern Americans are obese, their near cousins in Europe or Africa or Asia are not fat, even when there is an abundance of food back in the old country.
Mind, I'm not saying there may not be a biological basis to obesity. Behavior can actually change brain wiring. I'm saying there is no good evidence that obesity is genetically linked. Probably only identical twin studies could begin to establish that.
One interesting example out of many is an ongoing NIH study of obesity in Pima Indians in Arizona.
The bottom line is that for centuries we no longer are "hunters and gatherers" and, more recently, farmers. Consequently, our human phenotypic makeup has been adversely affected by the industrialization -- with the resultant decrease in physical activity and the increase in the consumption of fatty and hi-carb "processed" foods -- of America and much of the rest of the world.
The picture that I see emerging (I'm in the trenches while moving toward the end of my "day job" career)is that the adiposity that creeps up on increasingly sedentary and junk-food gobbling children and adolescents lead to changes in neuronal circuitry that has a startling degree of commonality with those seen in patients who become addicted to illicit drugs, tobacco, and alcohol.
It is now known that an individual's adipose tissue is not the physiologically inert sheet of blubber that it has been thought to be. And those who condemn obese individuals as gluttons, etc. are not standing on firm ground, both scientifically and morally speaking.
Addictive disorders can be seen to "set in" and become established when individuals are in adolescence. Indeed, susceptibility of adolescents to addictive disorders is a major issue in neurobiology, biological and social psychology and psychiatry today.
I predict and indeed hope and pray that advances in our understanding of the more "traditional" addictive disorders someday soon will be applied to the growing global scourge of obesity..........