Design of the SHAPE-2 study: the effect of physical activity, in addition to weight loss, on biomarkers of postmenopausal breast cancer risk.

Background: Physical inactivity and overweight are two known risk factors for postmenopausal breast cancer. Former exercise intervention studies showed that physical activity influences sex hormone levels, known to be related to postmenopausal breast cancer, mainly when concordant loss of body weight was achieved. The question remains whether there is an additional beneficial effect of physical activity when weight loss is reached.