Consider this an idle rumination, if you would.
Not terribly long ago, a study came to my attention. It noted that among women, lesbians tended to be heavier than bisexuals who in turn tended to be heavier than straight women. This was curious to me, as also, I have seen many studies over the years that seemed to indicate that straight women seem to care more about a partner's body fat percentage than straight men did, and anecdotally, it seems to me that gay men appear to care the very most about it.
Lo and behold, Google provides a study suggesting that yes, gay men worry more about weight than straight men. And I am tempted to say there are two factors - being male, and being interested in males - that both somehow become a driving force, and if straight women care more about body fat than straight men, then being interested in men would be the stronger fashion.
Nevertheless, it strikes me as very odd, and it would bother me very much more if I thought this phenomenon was more biological than social.