Studies show that the benefits of running for just 5 to 10 minutes at a moderate pace (6.0 miles per hour) each day may include: reduced risk of death from heart attack or stroke. reduced risk of cardiovascular disease. lower risk of developing cancer.
Professional marathon runners are also skinny because they train so hard to sustain endurance. This prevents their bodies from bulking up because they burn almost all the calories that they consume. Unlike sprinters, who need muscles, marathon runners don't need muscles at all.