Your body builds the strength necessary to support your activity level. Unless you already have an active exercise regimen, an overweight person has generally o

Your body builds the strength necessary to support your activity level. Unless you already have an active exercise regimen, an overweight person has generally only built the strength to support walking shorter distances. So the more overweight you are, the more careful you need to be when increasing distance while running. Alternatives like cycling and swimming are better for the knees, especially for the old and overweight.