Breats Cancer In Obese Women

Breast Cancer in Obese Women

One of the frightening aspects of breast cancer is that many of the known risk factors for the disease, such as family history, are beyond our control. But a recent study found that weight gain of 20 pounds or more increased risk of breast cancer in postmenopausal women.

In premenopausal women who are overweight, fat tissue appears to protect against breast cancer. Although fat tissue produces estrogen, obese women tend to ovulate less frequently than leaner women, so they have less estrogen circulating in their bloodstream; such estrogen can fuel the growth of certain types of breast cancer.

In older women, however, fat tissue increases breast cancer risk because the estrogen from parts of the body other than the ovaries becomes more important. "Because postmenopausal women don't have estrogen produced in the ovaries, the vast majority of estrogen in these women is produced in the fat tissue," explains coauthor Heather Spencer Feigelson, PhD, a senior epidemiologist at the Atlanta-based American Cancer Society.

In the study, published in the February issue of Cancer, Epidemiology, Biomarkers and Prevention, researchers analyzed 1,934 postmenopausal women with breast cancer. Weight gain of 21 to 30 pounds since age 18 was associated with a 40 percent increase in risk in women who had never used menopausal hormone therapy. Breast cancer risk doubled in women who gained 70 pounds or more, compared to women who stayed within five pounds of their 18-year-old weight.

Although no association between weight gain and breast cancer was seen in women who took menopausal hormone therapy, Dr. Feigelson says that their use of hormones, which contain estrogen, made it difficult for researchers to really determine if weight gain played a role in their risk.

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