Some say it's actually a disease. Others are sadly born with it. Others just become that way. People are generally getting bigger.
The question is, if a child becomes bigger and bigger, simply because he's always hungry and the parents pity the child (in the short term) being hungry and continuously feeding him because she can't stand the sight of her child wailing in hunger, could you blame her?
(I actually saw this over CNN many weeks back, so, it's not hypothetical.)