I never said I wanted intrusion, but there is a responsibility to project the vulnerable. What defines being at risk, from any of those factors, is a scientific, social, and political question, so I won't hazard an answer!
I do generalise but those are my two primary reasons. Of course individual cases have other dependent variables, like genes, hormones etc but the broad trend in overweight kids cannot be explained this way; it is mostly a product of social factors.
I haven't read the whole thread but I'd argue there are two main reasons for fat kids -
1. Not eating proper, home-cooked meals.
2. Drinking calories, coke etc, and tragically in recent years, energy drinks.
Parents are entirely to blame for the first problem, which typically leads to the second.