Pieman (aka Homer Simpson)

Not sure if its still around but at one point there was a Simpsons Super Hero comic. Was published infrequently as the Simpsons Superhero pool was quite limited.

Fat Mama! She's  hysterical

http://www.brandaofilms.com/images/Autographs/FatMama.JPG

Though it's hard to tell, as he recieved large muscles when he was given superpowers, but its the closest thing i can think of.

Fat Momma, from the first season of Who Wants to be a Superhero:

She came second. Somehow.

Catman (DC) used to be a fat loser.  I think that Blob from X-Men was a hero for a little while, too.

I had to resort to google but there is "Bouncing Boy" from Legion of Superheroes. I could probably think of 20 fat supervillains off the top of my head.  I guess fat people are evil.

-And with that, I must bid you all goodnight.  Here's a Futurama quote for ya:  "You make Fat Albert look like Regular Albert!"

SHREK

Damned if i hadn't forgotten him, especially given that he appeared in Justice League Unlimited (albeit briefly when they encountered the Legion).

I can't think of any but I'm sure there are many fat 'super-villains' though