Found a few videos I've found

Well, it's more stuffing than weight gain, but it's still pretty damn good.
And it's a form of expansion, even if it's just the belly.

Before you get off on the whole "Dubbing is evil" thing, keep in mind I'm just relaying information that I find.
And I'm too lazy to hunt for the subbed stuff.

This one is from Magical Play.
I haven't seen this series, nor the other one from that group(Azu Manga Daioh), but everyone always raves about it.
It's basically an eating contest, for a flower point, which is useful... for something...
http://youtube.com/watch?v=ukXBhaoh8no

Next is from Bobobo-bo-bobobo
It's a clip is after Suzu stuffs herself to an extreme.
I think it's a she...
There isn't really any process in this one, or a before/after picture, but I might as well toss it in since that rule's been torn asunder over the course of this year.
http://youtube.com/watch?v=dhJ_CR8EiTk

No clue about this one...
it's just a tad odd, so I tossed it in.
http://youtube.com/watch?v=QWe4v5U1PCo

This one is from that show 6teen.
The blonde girl gets a job at a chocolate shop, and just does what anyone else from a chocolate shop does.
Eat chocolate.
http://youtube.com/watch?v=2JWdTemVxS8

That's it for now, if I find more, I'll post `em.