Among postmenopausal women, intentional weight loss protects against endometrial cancer, even if that loss is modest (5% or more), according to a report in the Journal of Clinical Oncology.

Endometrial cancer is the malignancy most strongly associated with obesity, but to date few studies have examined the effect of intentional weight loss on risk. Researchers analyzed data from the prospective Women’s Health Initiative to assess this relationship in a large, ethnically diverse population of postmenopausal women with detailed records on potentially confounding factors such as body mass index, smoking status, physical activity level, hormone therapy use, parity, age at menarche, age at first birth, and family history.

They focused on 36,793 women who participated in the WHI and who reported whether they had maintained a stable weight, lost 5% or more of their total weight, or gained 5% or more of their total weight during the first 3 years after enrollment. During a mean of 11.4 years of follow-up, 566 of these women developed endometrial cancer, said Juhua Luo, PhD, of the department of epidemiology and biostatistics, Indiana University School of Public Health, Bloomington, and her associates.

Women who lost weight intentionally showed a significantly lower risk of endometrial cancer than did those who had stable weight (HR, 0.71). This association was most pronounced among obese women: Those who lost at least 5% of their body weight intentionally showed a dramatic reduction in endometrial cancer risk (HR, 0.44). In contrast, unintentional weight loss was not associated with a lower risk of endometrial cancer. And women who gained 10 pounds or more during the first 3 years of the study showed a significantly higher risk of endometrial cancer, the investigators said (J Clin Oncol. 2017 Feb 6. doi: 10.1200/JCO.2016.70.5822).

In a sensitivity analysis, women who intentionally lost weight and achieved a normal BMI showed the same risk of endometrial cancer as that of those who had maintained a stable BMI throughout the study.