Have you read the book, Gay Men Don't Get Fat? Its modeled after the successful (and cheeky) book, French Women Don't Get Fat.
According to the article in Gawker, "There is only one thing that keeps gay men in shape: fear. Yes, every gay—at least those of the stereotypical abdominal-obsessed physique that populates Fire Island and Palm Springs—is brought about because gay men are afraid that they will be alone for the rest of their lives."
I'm definitely prone to obsess about my weight and definitely have a far more intimate relationship with my gym (a.k.a. The Gay Temple) than any of my straight / heterosexual friends, but am I a walking cliche? What do you think? You can read the full article on Gawker, here.
UPDATE A reader pointed out that back in April I wrote a post called Is it vanity or health? The brief post was a question to readers who work out; what was their motivation. (Thanks for the reminder Mike.)
Thanks to Andy for pointing me to the article.