All right, the connection between obesity and environment is wrong. But if your thesis that obesity is 80% caused by genetics is correct, how comes that the US are the fattest country in the world? Just a lot of people with bad DNA? I think you grossly underestimades the effect that modern US lifestyle has on people with a predisposition to gain weight. Basically, (over)eating fast food, using a car to go everywhere and watching tons of TV do help making Americans similar to the Wally version of people.