Working out can do so much more than slim you down and build muscle. Exercise can also reduce you risk of both lung and breast cancer. According to two new studies, presented at the annual meeting of the American Society of Clinical Oncology, women who exercise vigorously -- using both weights and cardio several times a week-- reduced their risk of lung cancer by a third and their risk of breast cancer by 30%. The best part, exercising ladies saw these benefits even if the had other risks like smoking or being overweight. Now researchers need to figure out why exercise reduces these risks and how much you need to sweat to see the benefits. One possible answer: Exercise may reduce the number of fat cells that produce estrogen, a hormone which in excess has been shown to fuel breast cancer, Jyoti Patel, M.D., spokeswoman for the American Society of Clinical Oncology. Strength exercises like squats, bicep curls and chest presses may be particularly good for this. A 2012 Harvard study found that muscle strengthening exercises produce a hormone called irisin which travels through the body, altering fat cells in a way that speed up metabolism and burns more calories. When it comes to lung cancer, things are less clear. Ange Wang, M.D., says that "Physical activity might specifically help the lungs by improving lung function and limiting the deposition deep in the lungs of inhaled cancer-causing agents." She also said that exercise boosts the immune system and helps people lose weight -- both shown to help protect against cancer. Both studies found that the more time a women spent doing exercise of any kind, the more protected she was regardless of other risk factors. In the studies, the women exercised for 4-7 hours per week and it was noted that any level of intensity can help. "Our research seems to indicate that you don't have to kill yourself," Wang said. "It doesn't need to be strenuous. You just have to put the time in." What are you waiting for? Add some weight training to your routine today. Time for a healthy chest, inside and out.