According to a study
just released by researchers in Boston, gay men are 50% less likely to be obese than straight men. But lesbians are more likely to be overweight than straight women.
After scrutinizing a health survey of more than 67,000 Massachusetts residents between the ages of 18 and 64, the researchers found that 14 percent of gay men were obese versus 21 percent of straight men. The opposite was true of gay women: 26 percent were found to be obese, as compared with 17 percent of the straight women. The researchers also found that both gay men and gay women were more likely to be current smokers compared to their heterosexual counterparts. And gay women were more likely to have multiple heart disease risk factors than straight women.
Earlier studies that looked at health in the gay community focused mostly on sexually transmitted diseases and mental health, rather than on chronic illnesses like obesity and heart disease, says the study’s lead author Kerith Conron, an associate research scientist at Northeastern University and a research fellow at the Harvard School of Public Health. “This may mean that we in the public health community need to come up with more tailored messages to reach these groups, just as car dealers do when they want to reach a specific target audience,” she said. Conron suspects that cultural differences might at least partly explain the weight divide. It may be more acceptable in the lesbian community for women to be full-sized, she said.
The differences may be more tied up in male/female differences, rather than gay/straight, according to one scientist who says, "People in sexual relationships with men — heterosexual women and gay men — get more pressure to look thin and to otherwise conform to attractiveness norms than do people in sexual relationships with women — lesbians and heterosexual men."
Researchers at the CDC say obesity is far less prevalent in Canada than in the United States. And they don't really know why. 
