WASHINGTON, July 13 (UPI) -- Weight gain is related to an increased risk of breast cancer in postmenopausal women, while weight loss lowers the chance of developing the disease after menopause, a new study suggests.
In the new edition of the Journal of the American Medical Association, researchers analyzed the Nurses' Health Study, tracking nearly 50,000 women for up to 24 years to analyze weight changes after menopause.
"I think it's encouraging," said A. Heather Eliassen of Brigham and Women's Hospital and Harvard Medical School in Boston, who led the study. "We found that women who were able to lose weight after menopause, particularly women who lost weight and were able to keep it off, were at a lower risk of breast cancer than women who didn't lose weight."
Women who lost about 22 pounds or more after menopause, maintained a lesser weight and had never used postmenopausal hormones were at 57 percent lower risk of breast cancer. Postmenopausal hormone use has been found to increase the risk of breast cancer.
Women who had gained around 55 pounds or more since age 18 were at a 45 percent increased risk of breast cancer than those who had maintained their weight. Women who gained about 22 or more pounds since menopause experienced an 18 percent greater risk of breast cancer than those who remained one weight.
"We confirmed findings of previous studies that found an increased risk with weight gain after age 18, and we found that weight gain either before or after menopause was associated with an increased risk," Eliassen said.
Fat tissue produces estrogen, and therefore losing weight after menopause lowers circulating estrogen levels. Studies have found that estrogen is directly related to breast cancer, and therefore reducing the amount of estrogen is thought to decrease the risk of breast cancer.
"Weight is one of the few breast cancer risk factors that women can do something about," Eliassen said. "And our study suggests that it's never too late to lose weight to reduce breast cancer risk. But, in addition, knowing how difficult it is to lose weight, the best advice would be to avoid weight gain to begin with."
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