Mmm, definitely a tricky one. On the one hand it's good to see positive images of fat people of all ages; we do exist, and it's nice not to feel marginalised. It's also good that it's getting easier to buy clothes for children who need larger sizes - heaven knows the manufacturers are thin on the ground for larger adults, it's a positive step that clothes are available for larger children and they're not being made to feel like freaks by having to have their clothes specially made.
But. But. There are so many buts.
It's not healthy, and while I can't talk being the size I am, with a child it's a lot different. Weight and size is usually (I realise not always) about over-eating, and that's firmly under the control of the parents. It's miserable being an overweight adult; I can only imagine how awful it is to be an overweight child.
The claims that childhood obesity is a common problem, and that so many children are overweight that their parents don't notice it, tends to suggest that it's becoming seen as the norm, which is worrying if it's true. The kind of illnesses that are associated with weight are just as bad in a child as in an adult - worse in some respects because it's so much more unnecessary.
Everyone should be entitled to feel comfortable about themselves whatever their size - but when we're talking about children it's so much harder to feel that we should just accept obesity.