Wish I could agree but there is more to the picture. People also get fat because of treatments and medications. In my case, the entire family line has always been lean on fathers and mothers side both. I was quite lean till Grade 3 when I started haing severe headaches and also fainted once. On thorough checkup with MRI and CT scans some kind off infection was found in my lower part of brain and I had to undergo minor surgery and a strict medication for 3 years. It had some kind of steroids and I quickly gained weight. Though I am much more conscious about my fitness these days but I am never able to achieve the lean structure because my metabolism is very slow. I am almost 85 kgs with 1.8m of height but if you compare my diet with my friends with a leaner structure, you would be amazed at how I am bulky and they are not.

Sometimes, genetics and medical history have a role to play in your body structure. But yes obesity like the ones found in America is solely because unhealthy lifestyle and food eating patterns.