Women who exercise and maintain a healthy weight have a reduced risk of breast cancer even if their exercise is limited to mild recreational physical activity, according to the results of a study published early online in the journal Cancer.
Breast cancer is the most commonly diagnosed type of cancer (other than skin cancer) in U.S. women. Each year, roughly 227,000 women are diagnosed with breast cancer and close to 40,000 die of the disease.
There are a number of risk factors associated with breast cancer, including obesity, overweight, increased levels of circulating estrogen, and a sedentary lifestyle. Regular physical activity has been shown to improve overall health and wellbeing as well as reduce the risk of cancer. There is no doubt that exercise has benefit; however questions remain regarding the frequency, duration, and intensity required in order to provide benefit.
Researchers at the University of North Carolina analyzed data from women who participated in the Long Island Breast Cancer Study Project, which was designed to investigate possible environmental causes of breast cancer. The analysis included 1,504 women with breast cancer and 1,555 women without breast cancer who were between the ages of 20 and 98.
They found that women who exercised either during their reproductive or postmenopausal years had a reduced risk of developing breast cancer. Those who exercised 10 to 19 hours per week experienced the greatest benefit, with an almost 30 percent reduced risk of developing breast cancer. The risk reduction was observed across all levels of intensity—so even mild physical activity proved worthwhile.
One thing that could negate the benefits of physical activity: weight gain. In fact, when the researchers analyzed the joint effects of physical activity, weight gain, and body size, they found that women who experienced substantial postmenopausal weight gain, regardless of activity level, had an increased risk of developing breast cancer. The researchers concluded that physical activity—even just mild recreational physical activity—may reduce the risk of breast cancer, but weight gain might eliminate the beneficial effects.
McCullough LE, Eng SM, Bradshaw PT, et al. Fat or fit: The joint effects of physical activity, weight gain, and body size on breast cancer risk. Cancer. Published early online June 25, 2012. DOI: 10.1002/cncr.27433