@AC 15:51
I think the point was the someone who weighs 39 stone can't exactly do much with their child, given that they probably can't do much for themselves. Apart from sweat, eat, get out of breath and perform gravity-assisted feats of movie magic with Harrison Ford.
Glandular or not, mass comes from somewhere. In the case of humans it's food. Put less in, you put less on - it's simple. You don't get fat eating salad... just ask any vegetarian!!
There was an interesting documentary on Channel 4 recently about a massively fat kid who had every excuse in the book and a mother who kept pandering to his feeding habits which (some would say unsurprising) consisted of junk food, take-aways, and stuff of that ilk. When it came to "treating" him - i.e. cutting off the lard supply - he turned out to be incredibly weak-willed.
I guess some people are just happy needing the Fire Brigade's help to get out of the house. But one thing's for sure: people that fat can't exactly do all the meaningful active stuff with their kids that the rest of us can enjoy. Stuff that add an important layer of bonding and learning with their child.