Exercise is an appetite suppressant, sometimes delaying the return of hunger for hours. Exercise triggers the release in the brain of natural tranquilizing chemicals called endorphins, resulting in the relief of tension or depression that may prompt you to overeat.
Exercise builds up muscle tissue which burns calories at a higher rate than body fat.
This makes it possible to eat more without gaining or to lose more rapidly without changing caloric intake. Because muscle tissue takes up less space than the same weight of fat, active people look thinner than their sedentary counterpart who weigh the same. So even if you do not lose any weight, exercise will make you trimmer. For up to 15 hours after exercise the body continues to burn calories at a higher rate than it would have without exercise. In other words, exercise raises the body's idling speed for hours after exercise is over.