Although I do not care for WG, but here is something that you guys might have to look into.
It appears that she eats the kind of soup that Sumo wrestlers tend to eat that lets them gain weight and stay healthy. I guess this is some kind of magic soup causing her to gain weight quickly. And yes, she stays like that (don't know about the end though).
From:
http://katohayabusa.sakura.ne.jp/