I don't mean to be rude, but I think that the notion that Ganon is fat is kind of a stupid one.
http://zeldadungeon.net/forum/attachment.php?attachmentid=6577&d=1281977612
OoT Ganon here is obviously not, no question there.
http://zeldadungeon.net/forum/attachment.php?attachmentid=6576&d=1281977596
Same is true with TWW Ganon, sorry to say. Look, TWW had a stylized art-style. Looking at EVERY SINGLE CHARACTER IN THE GAME, the proportions are basically identical to Ganondorf. So is everyone in TWW fat? Obviously not. The notion that he's fat is ridiculous. Also notice that the biggest part of his body is his chest. In fact, his chest has incredible mass, so he's very muscular in TWW. Far more so than OoT. The only part of his belly that bulges does so to meet the shape of his chest, so there's no argument for him being fat here. Here's a second picture that makes it more obvious:
http://www.zeldawiki.org/images/2/28/WW_Ganon.png
Which means your best example is TP Ganon:
http://www.zeldawiki.org/images/5/5c/DarkLordGanondorf.png
http://www.zeldawiki.org/images/4/4a/DLGanon_TP.jpg
http://www.zeldawiki.org/images/5/5d/Ganondorfrender.png
Seriously? That looks fat? He's a big guy, obviously, but I see no fat here. His waist matches the size of his chest, but does not go past it. Actually, I'd say it's a little smaller still. Even if there is a little, pay attention to his pants. They're puffy, and this is true for all of his clothes. Additionally, he wears bulky armor, including plate-mail. While I guess he
could be fat under all that, there is no proof whatsoever because of all that armor.
HE. IS. NOT. FAT. >.<