Obese women may have a higher risk of developing ovarian cancer than their thinner counterparts, a large study of U.S. women suggests.

Ovarian cancer is a particularly deadly type of cancer because in the initial stages it typically has vague symptoms or none at all, making it difficult to catch early.

In the new study, which included more than 94,000 U.S. women ages 50 to 71, who were followed for more than 7 years, the researchers found that obese women were more likely to develop ovarian cancer. But the risk appeared to be confined to those who’d never used hormone replacement therapy (HRT) during menopause. Previous studies have linked hormone use to a reduced risk of ovarian cancer.

Among women who’d never used HRT, those who were obese had an 83 percent higher risk of ovarian cancer that normal-weight women did.

The findings, reported in the journal Cancer, suggest that obesity may be one of a few controllable risk factors for ovarian cancer.

They also offer women one more potential reason to avoid unhealthy weight gain, said lead researcher Dr. Michael F. Leitzmann, of the U.S. National Cancer Institute in Bethesda, Maryland and the University of Regensburg in Germany.

“Our data suggest that maintaining a healthy weight is associated with a reduction in the risk of developing ovarian cancer,” Leitzmann told Reuters Health.

It’s not entirely clear why obesity may contribute to ovarian cancer, but it may have to do with the effects of excess body fat on a woman’s estrogen levels, according to Leitzmann and his colleagues. The fact that the risk varied according to women’s HRT use supports this theory, the researchers note.

The study also found a link between obesity at the age of 18 and a higher risk of ovarian cancer later in life - a relationship was even stronger than the one between later-life obesity and ovarian cancer risk.

It’s possible, the researchers say, that weight in adolescence or young adulthood is even more relevant to ovarian cancer than weight gain later in life.

SOURCE: Cancer, February 15, 2009.