Being overweight in young adulthood or later in life may raise a woman’s risk of ovarian cancer, particularly if she’s never had children, researchers have found.

In a study of 2,110 women with and without ovarian cancer, researchers found that those who were relatively heavy, either in recent years or at the age of 18, were more likely than thinner women to develop the disease.

But the relationship between weight and ovarian cancer was strongest among women who’d never given birth. For them, cancer risk climbed in tandem with recent body mass index (BMI), a measure of weight in relation to height.

Among childless women, those who were obese in recent years had 2.5 times the risk of ovarian cancer compared with the thinnest women. The same pattern emerged when the researchers looked at the women’s weight gain since age 18.

Dr. Julia Greer and her colleagues at the University of Pittsburgh Medical Center report the findings in the journal Cancer.

A number of studies have looked at the relationship between body weight and ovarian cancer risk, with conflicting results. A connection is considered biologically plausible because excess body fat can raise levels of estrogen, as well as male sex hormones called androgens, which may in turn feed ovarian tumor development.

Pregnancy and childbirth are believed to lower the risk of ovarian cancer by reducing the number of times a woman ovulates in her lifetime, and therefore her estrogen exposure.

The new findings suggest that in overweight women who’ve had no children, the effects of excess body fat and “incessant” ovulation combine to raise the risk of ovarian cancer, according to the study authors.

Along with their greater estrogen exposure, these women may develop chronic inflammation in the ovaries as a result of continuous ovulation, the researchers speculate. This inflammation might then damage cells in a way that leads to cancer.

The findings offer yet another reason to maintain a healthy weight throughout life, Greer told Reuters Health. And that goes for all women, whether they’ve had children or not, she pointed out.

According to American Cancer Society estimates, Greer noted, at least one third of all cancer deaths in the U.S. each year are attributable to excess weight and obesity.

SOURCE: Cancer, May 15, 2006.