Women who gain weight during adulthood increase their risk of postmenopausal breast cancer whereas women who lose weight reduce it. In fact, gaining weight over time heightens the risk of breast cancer more than maintaining a high, but relatively stable, body mass index (BMI) over time. While gaining weight after a diagnosis of breast cancer increases the risk of recurrence, it is not clear whether losing weight improves prognosis.
Obesity increases aromatase activity (estrogen production) within the breast. Leptin, a hormone secreted mainly by fat cells, stimulates both the growth and proliferation of breast cancer cells. The heightened systemic inflammation associated with obesity also increases the risk of breast cancer.
The high circulating insulin and insulin resistance often associated with obesity also can stimulate breast cancer growth and impair prognosis independent of estrogen. Furthermore, fat tissue itself can directly promote cancer by providing a favorable environment for tumor growth. Fat cells within tumors have been found to be associated with increased tumor vascularization and increased proliferation of neighboring malignant cells. Now a new study has reported that exercise can reduce circulating markers of angiogenesis in overweight and obese postmenopausal women.

Latest research finds exercise reduces markers of angiogenesis

The study referenced at the beginning of this news story was designed to investigate the influence of weight loss and exercise on markers of angiogenesis, the growth of new blood vessels. Tumors must induce angiogenesis in order to grow beyond a very small size since they need a blood supply. However, angiogenesis is also required for fat tissue formation and maintenance. To conduct the study, the authors recruited 439 healthy but overweight or obese (BMI > 25 kg/m2) postmenopausal women between 2005 and 2008. Study participants were randomly assigned to one of four groups in a year-long study: (1) restricted calorie diet (goal: 10% weight loss, 118 participants); (2) aerobic exercise (225 minutes per week of moderate-to-vigorous activity, 117); (3) combined diet plus exercise (117); or (4) control group not assigned a calorie restriction diet or exercise program (87). Circulating levels of angiogenic biomarkers (vascular endothelial growth factor (VEGF), plasminogen activator inhibitor-1 (PAI-1), and pigment epithelium-derived factor (PEDF)) were assessed at the beginning of the study and after 12 months. The analysis was adjusted for BMI, age, and ethnicity.
Increasing weight loss was found to be significantly associated with increasing reductions in PAI-1, PEDF, and VEGF. Participants in the diet plus exercise arms had significantly greater reductions in PAI-1 at 12 months (−19.3%) than the controls (+3.48%). Participants in both the diet (−9.20%, −8.25%) and the diet plus exercise arms (−9.90%, −9.98%) also had greater reductions in PEDF and VEGF compared with controls. However, no differences were found for participants in the exercise arm compared to controls. The authors conclude that losing weight is significantly associated with reduced circulating markers of angiogenesis, and thereby could help prevent cancer in overweight and obese individuals.
Please see our article on obesity for more information.