The rise in childhood obesity is fairly recent and international.
Unless we're going to say that simultaneously, globally 1/3 of parents have become abusive in a way they didn't use to be, then to blame parents instead of looking at environmental and societal factors is futile and short-sighted.
Of course there's something else going on.
Everyone who has ever tried to lose (or gain) weight can tell you that it's far more complicated than calories in/out. There is esteem, metabolism, motivation etc to take into account. It is hard enough to lose (or gain) weight as an adult, I can't imagine trying to make an unmotivated, hungry child lose weight. And the potential to do psychological damage is huge.
Treats and 'special occasions' are everywhere you turn. School dinners have a pudding everyday. Nursery has a pudding every day. School days can be long, longer if they're at a cm or after school club, then after there's sometimes homework.
I think there's a very fine line between a child who's a healthy weight and one who is overweight, and I think far more of it is down to dumb luck than a lot of posters on this thread would have you believe.
Add to this conflicting info about healthy eating; most of us will have been raised believing low fat is good. More recently, it's looking like fat actually isn't that bad, but sugar is practically poison.
None of which means parents shouldn't try, of course they should, but in most cases, where they are failing, it's not abuse.
We really need to look far more as a society, about food and its role. I'd start by banning pudding in school dinners and stopping school from using Haribo as treats/prizes/presents.