Several studies have linked weight to the risk of breast cancer. However, the manner in which weight affects risk differs between pre- and postmenopausal women.
Before menopause, it appears that being somewhat overweight decreases a womanís risk of getting breast cancer.
After menopause, however, being overweight increases risk of the disease by about 20% to 60%. This relationship can be explained mainly by the fact that, after menopause, most of the natural estrogen in a womanís body comes from her fat tissue. And the more fat a woman carries after menopause, the more estrogen she will produce, which can increase breast cancer risk. Estrogen can stimulate the growth of estrogen receptor-positive breast cancers.
Itís important to note that, even though being overweight seems protective in premenopausal women, women should still avoid weight gain in adulthood. Women who became overweight in adulthood have a higher risk of breast cancer.
Also, women whose bodies are "apple"-shaped (i.e., women who carry their extra weight in their abdomen, rather than on their hips and thighs) have a higher risk of breast cancer.
Furthermore, extra weight that a woman puts on before menopause will likely remain during her postmenopausal years. It is important to note that nearly 80% of breast cancers occur in postmenopausal women. A very large study of nurses in the U.S. found that gaining 10 or more pounds after age 18 increased the risk of both developing and dying from postmenopausal breast cancer.
Achieving and maintaining a healthy weight to height ratio (i.e., body mass index) after menopause is important in lowering the risk of several diseases, including breast cancer.