Dose-response effects of aerobic exercise on adiposity markers in postmenopausal women: pooled analyses from two randomized controlled trials

Background/objective: Exercise may reduce the risk of breast cancer through adiposity changes, but the dose-response effects of exercise volume on adiposity markers are unknown in postmenopausal women. We aimed to compare the dose-response effects of prescribed aerobic exercise volume on adiposity outcomes. Participants/methods: Data from the Alberta Physical Activity and Breast Cancer Prevention (ALPHA) and Breast Cancer and Exercise Trial in Alberta (BETA) were pooled for this analysis (N= 720). These were 12-month randomized controlled trials, where participants were randomized to 225 min/week (mid-volume) of aerobic exercise versus usual inactive lifestyle (ALPHA), or 150 min/week (low-volume) versus 300 min/week (high-volume) (BETA). Fat mass and fat-free mass were measured using DXA and intra-abdominal and subcutaneous fat area were assessed with computed tomography. Results: After 12 months of aerobic exercise, increasing exercise volumes from no exercise/control to 300 min/week resulted in statistically significant reductions in BMI, weight, fat mass, fat percentage, intra-abdominal and subcutaneous fat area (P< 0.001). Compared with controls, fat mass loss was −1.13, −1.98 and −2.09 kg in the low-, mid- and high-volume groups, respectively. Similarly, weight loss was −1.47, −1.83, −2.21 kg in the low-, mid- and high-volume groups, respectively, compared to controls, and intra-abdominal fat area loss was −7.44, −15.56 and −8.76 cm²in the low-, mid- and high-volume groups, respectively, compared to controls. No evidence for a dose-response effect on fat-free mass was noted. Conclusion: A dose-response effect of exercise volume on adiposity markers was noted, however, the differences in adiposity markers were smaller when comparing 225 min/week to 300 min/week of exercise. Given the strong positive associations between obesity and postmenopausal breast cancer risk, this study provides evidence on the importance of exercise volume as part of the exercise prescription to reduce adiposity and, ultimately, postmenopausal breast cancer risk.