Physical inactivity and overweight are two accepted risk factors for breast cancer. However, because of their correlation it is not clear which is most relevant to risk. The investigators now set out to study whether physical activity in addition to weight loss by diet only, affects sex hormone levels, known to be related to breast cancer risk.

In the SHAPE-2 study 250 healthy overweight/obese and physically inactive women are randomly allocated to a diet-induced weight loss group, a combined exercise- and diet-induced weight loss group or a control group. The aim of the first two intervention groups is to loose 5-6 kg of bodyweight, either by dieting or mainly by increased physical activity. Measurements are performed at baseline and after 21 weeks, the end of the study period.

The aim of this study is to provide insight into the effect of weight loss mainly driven by exercise compared to equivalent weight loss due to nutritional calorie restriction on breast cancer biomarkers.

Postmenopausal women who are sedentary or overweight, have an increased breast cancer risk. It is suggested that these two factors mediate breast cancer risk mainly through sex hormone-related pathways. However, an inactive lifestyle and obesity are highly correlated and it is not clear which is most relevant to risk.

Literature shows that weight loss/ fat loss reduces postmenopausal sex hormone levels, but the question is if there is an additional beneficial effect on hormones of reaching this weight loss by physical activity instead of nutritional interventions.

In this three-armed, two-center intervention study, 250 sedentary postmenopausal women who are aged 50-69 years will first enter a run-in period of 5 weeks. During this period, all participants get a diet, adapted to the guidelines for healthy nutrition, meeting their energy expenditures to maintain stable weight. After this run-in phase they are randomly allocated to a (1) diet induced weight loss group, (2) a combined exercise and diet induced weight loss group or (3) a control group. Participants allocated to the dietgroup will get a calorie restricted diet of -500 kCal/day, they will remain their habitual exercise pattern. Participants in the combined group will follow an exercise programme (combined endurance and strength) of 4 hours of sports per week with an average energy expenditure of 350 kCal/day and a, less strict. And a calorie restricted diet of -250 kCal/day. The aim of both intervention groups is to loose 5-6 kg of body weight during the 14 week intervention period. Participants in the control group are requested to retain the baseline diet and their habitual exercise pattern. Primary study parameters measured at baseline and after 21 weeks are: serum concentrations of endogenous estrogens, endogenous androgens and sex hormone binding globulin. Other study parameters include: body fat distribution, amount of total and abdominal fat, weight, BMI, physical fitness, blood pressure and lifestyle factors.

The aim of this study is to provide insight into the effect of weight loss mainly driven by exercise compared to equivalent weight loss due to nutritional calorie restriction on breast cancer biomarkers. Furthermore, we are specifically interested whether weight loss mainly due to physical exercise induces greater amounts of fat loss (total and abdominal) and subsequently results in more favourable effects on these hormones compared to equivalent diet-induced weight loss.

Inclusion Criteria:

• Female
• 50-69 years of age
• Postmenopausal (>12 months after last menses)
• BMI 25-35 kg/m2
• Sedentary (<2 hours per week of at least moderately intensive activities (>4 MET))
• Willing to be randomly assigned to one of the three study arms
• Informed consent to participate in all screening and study activities.

Exclusion Criteria:

• Presently using sex-hormones

  • Maintenance use of corticosteroids
  • Suffering cancer (in medical history) except for non-melanoma skin cancers
  • Suffering type II diabetes mellitus or other endocrine related diseases
  • Smoking
  • Alcohol or drug abuse
  • Any disorder that might impede participation in the exercise programme
  • Following, or the intention to follow, a structured weight loss programme elsewhere

Analyses of the blood assays and MRI data were masked.