Fatness in fiction

Interesting post at Emerald City about using fatness as shorthand for evil in stories. Being a person of somewhat larger than average size (how's that for a euphemism), this concerns me a little when I read a story.
As Cheryl Morgan points out, fatness used to be an easy way to show a character was rich and a boil on society. Today, such a rich person -- say, Paris Hilton -- would most likely be rail thin and carved to "perfection" with plastic surgery.
I couldn't name any recent fiction that featured a main character who was both overweight and heroic in some manner. (I don't mean the traditional sense of daring-do hero, I just mean a character who tries to do the honest, right things.) I'm sure there's some out there, just not many.
Why hasn't this idea changed?