Postmenopausal women who have gained weight in adulthood are at greater risk of developing endometrial cancer than are women who maintain a stable weight, indicate the results of a study presented at the American Association for Cancer Research International Conference on Frontiers in Cancer Prevention Research, held October 22-25, 2011, in Boston, Massachusetts.

Obesity, as measured by body mass index (BMI), is an established risk factor for endometrial cancer in postmenopausal women. However, whether weight gain and weight cycling (yo-yo dieting) increase a woman’s risk for endometrial cancer independent of BMI is less clear.

To clarify these relationships, a team led by Victoria L. Stevens, PhD, the strategic director of laboratory services at the national home office of the American Cancer Society (ACS) in Atlanta, Georgia, collected data on 38,152 women included in the ACS’ prospective Cancer Prevention Study II Nutrition Cohort. All participants had an intact uterus and had provided information on weight history and weight cycling (defined here as the number of times a woman intentionally lost 10 pounds or more and then regained the weight) on the 1992 baseline questionnaire.

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By June 30, 2007, endometrial cancer was diagnosed in 560 of the women. Total weight gain during adulthood was statistically significantly associated with endometrial cancer risk: The disease was 4 times more likely to be diagnosed in women who had gained at least 61 pounds in that time frame than in women who had maintained their weight. After adjusting for baseline BMI, a twofold increased risk remained, but no link was found between weight cycling and endometrial cancer risk.  

The findings suggest that both adult weight gain and BMI might have independent effects on the risk of endometrial cancer. The researchers note that this underscores the importance of avoiding adult weight gain. The absence of an association between weight cycling and endometrial cancer incidence after adjustment for BMI suggests that cycles of intentional weight loss followed by regain do not contribute to disease risk. This indicates that encouraging women to lose weight is worthwhile even if the weight is subsequently regained.