CHICAGO, IL— Weight loss associated with physical exercise and caloric restriction together appears to reduce breast cancer risk-modulating hormones among postmenopausal women more than dietary weight loss without exercise, according to results from the SHAPE-2 trial presented at the 2014 American Society of Clinical Oncology (ASCO) Annual Meeting.
“Exercise is the preferred weight loss strategy to decrease breast cancer risk,” concluded lead author Anne Maria May of the University Medical Center Utrecht, in Utrecht, Netherlands, and coauthors. “Exercise-induced weight loss resulted in stronger favorable effects on breast cancer related serum sex hormones, mainly androgens and SHBG (sex hormone binding globulin) than diet-induced weight loss, demonstrating the importance of exercise for postmenopausal breast cancer risk reduction. Compared with diet induced weight loss, equivalent weight loss by exercise has more beneficial effects on body composition, with more fat loss and less lean mass loss.” There are several proposed mechanisms for this association, including reduced levels of inflammatory cytokines, reduced insulin, and reduced levels of circulating sex hormones. Exercise intervention studies suggest that physical activity influences breast cancer related sex hormone levels mainly through concordant weight loss, she explained.
To determine if patients with breast cancer enjoy additional exercise benefits aside from those associated with weight loss, the authors randomly assigned a total of 243 inactive, overweight, postmenopausal women to an energy-restricted diet study arm (n=97), a 16-week endurance (4 hours/week) and strength training exercise plus small caloric intake restriction arm (n=98), or a “stable weight control” control group (n=48). Women on hormone therapy and smokers were not eligible to participate in the study.
At baseline and 16 weeks, serum estrone levels, free estradiol, androstenedione, free testosterone, and SHBG were measured.
“Both interventions—diet and exercise—showed favorable effects on sex hormones compared to control,” May said. Exercise was associated with reduced body fat, and with reduced sex hormones and breast cancer risk.
“Probably the effects on sex hormones are largely mediated by weight or fat loss,” she concluded.
SHBG effects were significant in both the exercise and diet arms of the study (Ps < 0.0001); there was a non-statistically significant trend for a larger effect on SHBG among women in the exercise group than the diet arm of the study (P = 0.07).
- May AM, van Gemert W, Peeters P et al. Abstract 1504. Presented at: 2014 American Society of Clinical Oncology Annual Meeting; May 30-June 3, 2014; Chicago, IL.