A new study finds that women who lost weight after age 50 and kept it off had a lower risk of breast cancer than women whose weight remained stable, helping answer a vexing question in cancer prevention.1 The reduction in risk increased with the amount of weight lost and was specific to women not using postmenopausal hormones.
Lauren Teras, PhD, Senior Principal Scientist, Epidemiology Research, at the American Cancer Society, and lead author of the study, reported in a news release, “Our results suggest that even a modest amount of sustained weight loss is associated with lower breast cancer risk for women over 50.”
In the United States, more than two in three adult women are overweight or obese. And although high body mass index is an established risk factor for postmenopausal breast cancer, there has not been adequate evidence to determine whether that risk is reversible by losing excess weight.
Weight Loss and Breast Cancer Risk
To learn more, investigators from the American Cancer Society, Harvard T.H. Chan School of Public Health, and others used the Pooling Project of Prospective Studies of Diet and Cancer to estimate the association of sustained weight loss in middle or later adulthood on subsequent breast cancer risk. Their analysis included more than 180,000 women aged 50 years and older from 10 prospective studies. The new analysis is the first with a large enough sample size to examine the important question of whether sustained weight loss can impact breast cancer risk with statistical precision. Weight was assessed three times over approximately 10 years: at study enrollment, after about 5 years, and then again about 4 years later.
The results showed that women with sustained weight loss had a lower risk of breast cancer than women whose weight remained stable, and the larger the amount of sustained weight loss, the lower the risk of breast cancer. Women who lost 2 to 4.5 kg (about 4.4–10 lb) had a 13% lower risk (hazard ratio = 0.87, 95% confidence interval = 0.77–0.99) than women with stable weight. Women who lost 4.5 to 9 kg (10–20 lb) had a 16% lower risk (hazard ratio = 0.84, 95% confidence interval = 0.73–0.96). Women who lost 9 kg or more (more than 20 lb) had a 26% lower risk (hazard ratio = 0.74, 95% confidence interval = 0.58–0.94).
In addition, women who lost 9 kg or more and gained some (but not all) of the weight back had a lower risk of breast cancer than did those whose weight remained stable (hazard ratio = 0.77, 95% confidence interval = 0.62–0.97).
Dr. Teras commented: “These findings may be a strong motivator for the two-thirds of American women who are overweight to lose some of that weight. Even if you gain weight after age 50, it is not too late to lower your risk of breast cancer.” ■
Disclosure: For full disclosures of study authors, visit http://fdslive.oup.com/www.oup.com/pdf/production_in_progress.pdf.