I came across a comment somewhere recently, maybe even here, where it was said that even with a genetic predisposition to obesity, if you are born in a third world country in a life where poverty & food scarcity are your reality, then you obviously will never be able to become obese.
I completely believe in the fact that a predisposition to obesity is genetic, but I also buy the concept that it needs an environmental trigger. Assuming this is what is happening, it explains a lot about our obesity epidemic that has arisen over the past 50 years. The change in food supply and availability over the past 50 years is incredible. I can see how it could awaken a dormant predisposition to obesity in the population.