A new report for the first time suggests that being overweight increases a woman's risk of ovarian cancer, one of a growing list of cancers now linked to obesity or excess body fat.
Researchers have examined the link between excess body fat and ovarian cancer for years, with mixed results. Today's report, released by the American Institute for Cancer Research and World Cancer Research Fund, is the first to find that being overweight is a "probable" cause of ovarian cancer.
Researchers note that the increase is modest: A 5-point increase in a woman's body-mass index , or BMI, increases her risk of ovarian cancer 6%. Body-mass index is a ratio of a person's height and weight. A BMI above 25 is considered overweight, while a BMI over 30 is obese, according to the National Institutes of Health.
The new report finds other weaker evidence to suggest that breastfeeding can reduce the risk of ovarian cancer, although the report calls this evidence "limited" and "suggestive" rather than definitive. Wright notes that there is also good evidence that taking oral contraceptives reduces ovarian cancer risk, because it reduces the number of times that a woman ovulates.
Obesity is already linked to a variety of tumors, including those of the colon, uterus, esophagus, kidney, gallbladder, thyroid and pancreas, as well as postmenopausal breast cancer, according to the National Cancer Institute.
Maintaining a healthy weight could prevent about one in five of these cancers, or more than 120,000 a year, according to the American Institute for Cancer Research.
Losing weight offers much more dramatic benefits in terms of reducing other illnesses, such as diabetes and heart disease, notes Alexi Wright, medical oncologist at the Susan F. Smith Center for Women's Cancer at Boston's Dana-Farber Cancer Institute. And she notes that that weight has the biggest effects on certain subgroups of women, including those who are premenopausal and who haven't taken hormone replacement therapy.
For those looking for a way to drastically reduce the risk of ovarian cancer, losing weight "is not a slam dunk," Wright says. However, women may welcome the news, because "this is something you can do something about. You can't change who your mother was or whether your mother had ovarian cancer. There is overwhelming evidence that exercise and avoiding obesity improves lots of health conditions."
Ovarian cancer is diagnosed in 22,400 American women every year and kills more than 14,000, according to the American Cancer Society. It is a particularly feared cancer because it often causes no clear symptoms until it has spread too far around the body to cure. About 43% of patients survive at least five years.
Ovarian cancer has claimed the lives of many prominent American women, including actresses Gilda Radner and Madeline Kahn, as well writer Barbara Park, author of the popular Junie B. Jones children's books, who died in November at age 66.
Although the American Cancer Society's Alpa Patel called the increase in ovarian cancer risk from being obese "modest," she said the report is significant, because it gives women a way to reduce their risk.
"While this is no magic bullet, any way to reduce the risk of this deadly cancer , especially something like keeping a healthy weight, which has a role in overall cancer prevention, is worth acting on," Patel says.