OBJECTIVE:

We examined the effects of an aerobic exercise intervention on adiposity outcomes that may be involved in the association between physical activity and breast cancer risk.

DESIGN:

This study was a two-centre, two-armed, randomized controlled trial. The 1-year-long exercise intervention included 45  min of moderate-to-vigorous aerobic exercise five times per week, with at least three of the sessions being facility based. The control group was asked not to change their activity and both groups were asked not to change their diet.

SUBJECTS:

A total of 320 postmenopausal, sedentary, normal weight-to-obese women aged 50-74 years who were cancer-free, nondiabetic and nonhormone replacement therapy users were included in this study.

MEASUREMENTS:

Anthropometric measurements of height, weight and waist and hip circumferences; dual energy X-ray absorptiometry measurements of total body fat; and computerized tomography measurements of abdominal adiposity were carried out.

RESULTS:

Women in the exercise group exercised a mean of 3.6 days (s.d.=1.3) per week and 178.5  min (s.d.=76.1) per week. Changes in all measures of adiposity favored exercisers relative to controls (P<0.001). The mean difference between groups was: -1.8  kg for body weight; -2.0  kg for total body fat; -14.9  cm(2) for intra-abdominal fat area; and -24.1  cm(2) for subcutaneous abdominal fat area. A linear trend of greater body fat loss with increasing volume of exercise was also observed.

CONCLUSION:

A 1-year aerobic exercise program consistent with current public health guidelines resulted in reduced adiposity levels in previously sedentary postmenopausal women at higher risk of breast cancer.