Study Finds Moderate Weight Loss Reduces Levels of Sex Hormones Linked to Breast Cancer Risk
Even a moderate amount of weight loss can significantly reduce levels of circulating estrogens that are associated with an increased risk of breast cancer, according to a study by researchers at Fred Hutchinson Cancer Research Center – the first randomized, controlled clinical trial to test the effects of weight loss on sex hormones in overweight and obese postmenopausal women, a group at elevated risk for breast cancer.
The findings by Anne McTiernan, M.D., Ph.D., and colleagues were published in the Journal of Clinical Oncology.
"Based on previous research, our results suggest that losing just 5 percent or more of one's weight could cut by a quarter to a half the risk for the most common, estrogen-sensitive breast cancers," said McTiernan, director of the Hutchinson Center's Prevention Center and a member of its Public Health Sciences Division. McTiernan cautions that these findings only apply to overweight or obese women who are not taking hormone-replacement therapy.
Epidemiologists have long noted a link between obesity and increased risk of postmenopausal breast cancer. A relationship between body fat and estrogen production is thought to contribute to this risk.
The study was based on data from 439 overweight-to-obese, sedentary, Seattle-area women, ages 50 to 75, who were randomly assigned to one of four groups: exercise only (mainly brisk walking), diet only, exercise plus diet and no intervention. At the end of the study, participants on the diet-only and diet-plus-exercise arms lost an average of 10 percent of their starting weight, which was the goal of the intervention.