I remember seeing a programme about overweight kids, though not as extreme as that.
One mother said she didn't know what to do, she didn't understand why her child was so overweight.
They looked in the fridge.
It was full of junk, fatty carbs, etc. No veg or salad, or even fresh fruit. The cupboards were full of biscuits, crisps, chocolate,,etc.
I dare say it's the same for a lot,of overweight kids.
I don't make a habit of looking in other people's trolleys, but when there's a fat person ahead of me in the queue, and virtually every item they put on the checkout is carb/sugar heavy, processed stuff - and not necessarily cheap stuff, either, before anyone cries 'poverty!' - you can't help putting 2 and 2 together.
And I just don't believe that people really don't know what constitutes relatively healthy food. They just prefer the other sort, and have brought up their kids to,prefer it likewise..