Overweight and obese postmenopausal women are a group at elevated risk for breast cancer. Now, researchers at Fred Hutchinson Cancer Research Center report that even a moderate amount of weight loss can significantly reduce levels of circulating estrogens that are associated with an increased risk of breast cancer.
The findings of this first randomized, controlled clinical trial on the effects of weight loss on sex hormones in overweight and obese postmenopausal women by Anne McTiernan, MD, PhD, and colleagues are published in the Journal of Clinical Oncology.
“Based on previous research, our results suggest that losing just 5% 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. However, McTiernan cautions that these findings apply only to overweight or obese women who are not taking hormone-replacement therapy.
McTiernan and colleagues studied data from 439 overweight-to-obese, sedentary, Seattle- area women aged 50 to 75 years. Patients were randomly assigned to 1 of 4 groups: exercise only (mainly brisk walking), diet only, exercise plus diet, and no intervention. At the conclusion of the study, participants on the diet-only and diet-plus-exercise arms lost an average of 10% of their starting weight.
Researchers measured the effects of diet- and exercise-related weight-loss on blood levels of several types of sex hormones, including:
Significant reductions in hormone levels were discovered among the women who received dietary weight loss intervention. However, the most prominent results were among those who both dieted and exercised:
A beneficial impact on hormone levels was noted when patients lost as little as 5% of their total body weight, and the effect increased with the amount of weight lost.
“The amount of weight lost was key to changes in hormone levels,” McTiernan said. “The biggest effect was through diet plus exercise; exercise by itself didn’t produce much of a change in weight or estrogen.”
The results of the study could also be applicable to overweight women taking breast cancer prevention drugs such as tamoxifen, raloxifene, and exemestane. “None of these medications are recommended for use beyond about 5 years, and they can have significant side effects in some women. Therefore, women need long-term solutions for managing their risk,” McTiernan said. “Weight loss represents an additional option for long-term breast cancer risk reduction without significant or bothersome side effects.”
Source: Fred Hutchinson Cancer Research Center.
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