Run less and you may live longer. That is the takeaway from a recent study presented at an annual meeting of the American College of Sports Medicine. People who jog fewer than 20 miles a week at a relatively slow pace – 10 to 11 minutes per mile – tend to live longer than those who run more mileage at a faster clip of seven minutes per mile. "It appears almost all the cardiovascular and health benefits of exercise are obtained in the first 35 to 40 minutes – after that, you're only burning calories and improving at your sport," says study co-author Dr. Carl Lavie, a cardiac specialist at the Oschner Medical Center in New Orleans. Running too much may even be "cardio-toxic," because it can cause scarring and structural changes to the heart, he says. But don't throw out your running shoes: People who jog, whether it's five or 50 miles a week, still have a 19 percent lower risk of dying sooner than those who don't, the study concluded.