Women with lower amounts of total body fat have a lower risk of developing breast cancer, says Dr. Beth Overmoyer, an oncologist at Harvard-affiliated Dana Farber Cancer Institute. But what is the best way to get there? A study published online July 16, 2015, by JAMA Oncology found that among 400 postmenopausal women who were previously inactive, those who did 300 minutes per week of moderate- or high-intensity exercise had more success at reducing total fat after one year than those who exercised for the 150 minutes per week currently recommended. While this study did not measure the risk of developing breast cancer, combining its results with past studies "shows that five hours of exercise is superior to two hours. So yes, women should exercise more," says Dr. Overmoyer.