Reduced Breast Cancer Risk Associated With Weight Loss in Postmenopausal Women


Weight loss was associated with a reduced risk for breast cancer among postmenopausal women, according to research presented at the San Antonio Breast Cancer Symposium (December 5-9, 2017; San Antonio, TX).

Prior studies have shown that women with higher body mass index (BMI) may have an increased breast cancer risk, but few have investigated whether weight loss can lower the risk. Approximately 65% of women in the United States are considered overweight or obese based on BMI calculations.

“Obesity rates have been increasing in the United States,” said Rowan Chlebowski, MD, PhD, City of Hope Comprehensive Cancer Center (Duarte, CA). “We wanted to determine if there was a link between obesity and breast cancer risk.”

Researchers reviewed data from 61,335 women enrolled in the Women’s Health Initiative Observational Study. All participants were aged between 50 years and 79 years, with a normal mammogram and no prior breast cancer on study entrance, and a BMI ≥ 18.5.

Height and weight measurements were taken at baseline and repeated following 3 years. At baseline, 41% of participants were considered normal weight by BMI standards; 34% were overweight and 25% were obese.


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After a median follow-up of 11.4 years, 3,061 developed invasive breast cancer. Dr Chlebowski and colleagues observed an association between weight loss and reduced cancer risk. Women who experienced a weight loss of ≥ 5% were 12% less likely to develop breast cancer; the reduction increased to 37% in women who lost ≥ 15%.

Weight gain was not associated with increased risk for overall breast cancer. However, weight increases ≥ 5% raised triple-negative breast cancer risk by 50%.

“In the 3-year window of this study, relatively modest weight loss was associated with significant lowering of breast cancer incidence,” Dr Chlebowski said. “From this study, we have evidence that a weight loss strategy can be effective in lowering breast cancer risk in postmenopausal women.”—Cameron Kelsall