What also matters is how much you weigh and how many calories you burn. Being overweight and inactive appears to foster cell division and proliferation, which may give rise to tumors. Obesity also goes hand in hand with high insulin levels and inflammation, two metabolic states that help cancers grow and spread. "It is just now becoming apparent that obesity is a major risk factor for several cancers," says cancer researcher June Stevens, chair of the department of nutrition at the University of North Carolina. "Physical activity tends to be protective. So people should think about losing weight and being physically active to prevent cancer. Of course, if they lose weight by being more physically active and eating more fruits and vegetables and less red meat and alcohol—so much the better!"