Nothing's simple in obesity. But this guy talks about marathon runners who have to watch their weight...Doesn't smoking factor into this somewhere? 50's and 60's were huge smoking times. "Have a Lucky instead of a sweet."
I don't think it is simple as one item. There's a combination of many things converging on this obesity epidemic.
I just discovered if I'm 5'2" I'm obese and if I'm 5'3" I'm "overweight" per BMI - no way to enter 5'2 1/2" which is what I am. I shrank.