Overweight and obese women have more sex than skinny types, a new study suggests.

The research, announced today, is based on data on more than 7,000 women collected in the 2002 National Survey of Family Growth. The new analysis looked at the relationship between body mass index and sexual orientation, age of first intercourse, number of partners and frequency of intercourse.

The results seem to contradict stereotypes that overweight and obese women have less sex. If anything, the researchers said, the opposite seems to be true.

Researchers suspect the stereotype could mean overweight women get different messages than thinner women from physicians regarding pregnancy and sexually transmitted disease prevention, and that their sexual behavior might therefore vary.

"Some medical practitioners may not do appropriate follow-up with women who are overweight; they might assume they aren't having sex unless they are told otherwise," said Oregon State University Professor Marie Harvey, a specialist in women's sexual and reproductive health issues.

"Our analysis demonstrated that obese and overweight women do not differ significantly in some of the objective measures of sexual behavior compared to women of normal weight," said Harvey's colleague, Bliss Kaneshiro, an assistant professor at the School of Medicine at the University of Hawaii. "This study indicates that all women deserve diligence in counseling on unintended pregnancy and STD prevention, regardless of body mass index."

The survey relied on self-reports, however, and other studies have found that people often lie in sex surveys. The results were detailed in the September issue of the journal Obstetrics & Gynecology. A different study in 2006 concluded that obesity, as well as smoking, does curb sex.

Kaneshiro said the data showed that overweight women were more likely to report having sexual intercourse with a man, even when researchers controlled for age, race and type of residence. Ninety-two percent of overweight women reported having a history of sexual intercourse with a man, as opposed to 87 percent of women with a normal body mass index.

"These results were unexpected and we don't really know why this is the case," Kaneshiro said.

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