"And have you noticed that children born of fatter parents are more likely to be fat, even though the offspring born when the parents were svelt are more likely to be svelt. A statistical observation not a guarranteed result."

Actually, while that doesn't surprise me, that alone is still not evidence in favor of genetics since you also tend to learn your eating and exercise habits from you parents, too.

It's ridiculous to blame it all on any one factor, anyway. Some people are going to be genetically thinner than others, some people better their odds with good eating and exercise habits, whatever. I'm about average weight. I will never be a fashion model; I could starve myself to death and would still be pear-shaped (skinny upper body, butt and thighs like a bulldog Quarter Horse). I don't have a high metabolism; if I ate a lot of heavy food, I'd definitely be fat. So, I don't eat a lot of fried food, try to eat a lot of vegetables, and get some exercise. However, somebody else with different genetics might be rail-thin with the same habits. Another person might be 250 pounds. We're not all going to be the same, but most of us--barring serious health problems--can at least make the best of whatever genetics we have. Very, very, few people are going to hit 300 lbs on genetics alone; eating and lack of exercise are almost always contributors.

My mother is fat. Her family is more prone to weight gain than most, she tends to eat a lot of heavy food, doesn't exercise, and is on medications that put on pounds. She will always be somewhat fat because she has to be on steroids but she would be less fat if she ate better and moved more.