..Compared with women with stable weight (± 2kg), women with sustained weight loss had a lower risk of breast cancer. This risk reduction was linear and specific to women not using postmenopausal hormones (>2-4.5kg lost: Hazard Ratio (HR)= 0.82, 95% confidence interval (CI): 0.70-0.96; >4.5-<9kg lost: HR = 0.75, 95% CI: 0.63-0.90; ≥9kg lost: HR = 0.68, 95% CI: 0.50-0.93). Women who lost ≥9kg and gained some (but not all) of it back were also at a lower risk of breast cancer. Other patterns of weight loss and gain over the two intervals had a similar risk of breast cancer to women with stable weight.
These results suggest that sustained weight loss, even modest amounts, is associated with lower breast cancer risk for women aged ≥50 years. Breast cancer prevention may be a strong weight loss motivator for the two-thirds of American women who are overweight or obese.