I think its not just school, needmorecoffee. We walked *everywhere!" We lived in a less paranoid society where children were allowed far more freedom. At my son's age I was going down to the bakery to get bread. I suspect that if my son did something similar I would get reported to social services. Also children played out more.
There needs to be far more education about portion control. You can get over weight on a good diet. It happpened to my son when he was at nursery. He had breakfast at 6am, then had breakfast at nursery, lunch, supper at 4pm and then he wanted to eat with us. Those extra meals made him fat. However he is slimming out nicely, but it has taken two years to get to where he is.
It also needs to be understood that there is no quick fix for getting a child to a normal weight. For a child to lose weight healthily takes months and possibly years, depending on the extent of the problem.
My fear is that without proper education adults will put their children on yo-yo diets. That will truely produce a generation of obsese kids.