Men need to run approximately 25 miles each day, and women need to run 21 miles per day to lose 15 pounds in a month. Based on figures in Runners World, these figures assume that individuals are running five days a week and are not making any other lifestyle changes.
According to Runners World, a 2004 study found that on average, men burned 124 calories while running a mile, whereas women burned 105 calories. According to the Mayo Clinic, 1 pound of fat is the equivalent of 3,500 calories. Accordingly, a person needs to burn an additional 52,500 calories in a month through exercise or reduce caloric intake by that figure to lose 15 pounds.