Effect of Exercise on Postmenopausal Sex Hormone Levels and Role of Body Fat: A Randomized Controlled Trial

Purpose To examine the effects of a 1-year exercise intervention on sex hormone levels in postmenopausal women and whether any effects are mediated by changes in body fat composition. Methods We randomly assigned 189 sedentary postmenopausal women (age 50 to 69 years, body mass index of 22 to 40 kg/m(2)) to an exercise intervention (n = 96) or a control group (n = 93). The intervention combined aerobic and strength training and comprised supervised group sessions and home-based exercises (a total of 2.5 h/wk). Between-group differences in sex hormone levels (at baseline and 4 and 12 months) were examined with generalized estimating equations. Results In total, 183 women (97%) completed the study. Overall, the exercise intervention did not result in favorable effects on sex hormone levels. Among women who lost more than 2% body fat, declines in all estrogens were not significantly different between exercisers and controls. Androgen levels decreased significantly in the exercise group who lost body fat compared with their peers in the control group. Furthermore, this study confirmed that fat loss was significantly associated with declines in postmenopausal estrogen levels. Although not significant, a similar trend was observed for the androgens. Conclusion This study confirms that fat loss is associated with changes in postmenopausal sex hormone levels and suggests that exercise may be effective in inducing favorable changes in these hormones. J Clin Oncol 27:4492-4499. (C) 2009 by American Society of Clinical Oncology