Whilst I think that the title of the thread did read rather "inflamatory" I think that, taking the emotive stuff out, I do agree with pingu in principle... and with the causes !!!
and dont find it odd to discuss here.... after all this is mums net so maybe its relevant that mums would have a point of view on it and maybe have suggestions as to how we tackle the issue ????
I am a grandmother so do have a longer numbner of years to reflect back on than younger mothers and yes, I do think there are more overweight children now..... although schools are definately becoming more proactive in trying to do something about it.
I speak as someone who has been for a few years now obese for various reasons, some medical and some psychological, but who has always been very active and quite fit really and tried to eat healthily.
but that "healthy eating" might be part of the problem as I have been finding out from doing a lot of research as I am on the cusp of diabetes and testing to find what sends my blood sugar high.
- As said earlier MOST of the "low fat" / "lighter" options we have been conditioned to buy are packed full of sugar and carbohydrates
- we are encouraged to base all of our meals on carbohystrates by the health profession.... and as most of it does not taste good on its own it cries out for the addition of fats like butter, cheeses, sauces (negating the "low fat" yohurts etc we buy thinking we are being "good"
- even healthy fruit contains a lot of sugar as do "healthy" fruit juices
- we think cereals are healthy but manyh are packed full of sugars too .
All this is if we as carers and making great effort to encourage our children ( and DGC) to eat the "right things" ....
but then that can be hard because as a society we have changed .........
when I was a child ( 50 odd years ago) there was just no "low fat", healthy options we just ate "real" food and as long as we were sensible with portions we did just fine. Now many cheap and easy foods are processed stuff with all sorts of additives and there's proportionally a lot of calories in quite small portions. We also "expect" bigger portionss to fill our plates.
There was only one "takeaway" in our town which was the chip shop.... but it was a rare treat rather than a regular occurence.... same with the burger bar in the next town. Nowadays we are spoilt for choice with takeaways, restaurants and pubs featuring far more in our lives ......... its almost weekly ( if not daily) occurrence to go for a drink ( and a cake) in a cafe.
The tv also daily bombards us all with the social / pleasure aspect of eating, it can be hard to avoid all the programmes and adverts that encourage us, and kids, to partake in the pleasure that is eating.
Sweets also are far more readily available than when I was a child...... and children do see to have more expectation of them regularily or as a reward for something.
We did not have a tv and played outside in all except the worst weather ...climbing trees, playing hopscotch and skipping etc. Not saying kids never do that these days because I do see them do it, just that I do think it might be relevant, there is less freedom for children to do that these days.
I do think that there are definately some people that can eat anything they like , do little exercise and still be slim. I lived next door to parents like that some years ago who started to give their children proportionately the same amount of food they ate and the children both became podgy.
I personally could not eat even half what those adults ate, I exercised (hard circuits training for raft racing) as well as playing sports ... and easily put on weight if I did not judge it just right........ not flipping fair 
There are some medical conditions / medications that do cause weight gain so that sometimes makes it harder for some people so we cannot just look at someone ...... adult or child...... and make an assupmtion that (s)he is lazy / greedy / ignorant.
For sure its a complex issue that will NOT go away by browbeating anyone (people well aware of the medical side effects of smoking and binge drinking still do it 
.