Fat may fuel breast cancer growth.

M aintaining a healthy weight and exercising regularly have become standard advice for lowering the risk of breast cancer. But researchers are finding that these lifestyle changes may also be associated with better survival and lower recurrence in women with breast cancer. New evidence from several fronts suggests that excess body fat promotes breast cancer growth and that reducing body fat and increasing physical activity improve the odds of survival. Results of the Million Woman Study, a longitudinal cohort study of 1.2 million women in the U.K., concluded that being overweight or obese is associated with a higher risk of post-menopausal breast cancer and lower survival. The report, published in December in the British Medical Journal , also found an association between high body mass index and other cancers, such as endometrial cancer and cancer of the esophagus. That report, along with several other large prospective studies, should put to rest any doubt that excess weight contributes to the risk of developing breast cancer after menopause, said Heather Eliassen, Sc.D., an epidemiologist at the Harvard School of Public Health in Boston and a lead investigator in the Nurses' Health Study. The confusion has been over the observed inverse association between weight and premenopausal breast cancer. Carolina at Chapel Hill and colleagues at four collaborating institutions studied long-term outcomes of 1,508 women diagnosed with breast cancer between 1996 and 1997 as part of the Long Island Breast Cancer Study Project. The researchers looked at whether weight gain before diagnosis is associated with breast cancer survival. They reported in the journal Cancer Epidemiology, Biomarkers and Prevention in September that 5 years after diagnosis, 84% of obese women were alive versus 94% of nonobese women. Further analysis showed that for every 7 pounds of weight gained after age 18, the risk of dying from breast cancer increased 7%. When they looked specifically at women who were premenopausal at diagnosis, those who had gained less than 35 pounds were at little increased risk, but those who had gained more than 35 pounds had a twofold-increased risk of dying of breast cancer. Among those who were postmenopausal at diagnosis, weight gain of 30 pounds or more since age 50 was associated with a threefold increase in the risk of dying. After diagnosis, breast cancer survivors who gained more than 22 pounds had an increased risk of dying of breast cancer, according to a study presented …