Knowing your body composition can help you formulate an exercise program and set sensible fitness goals. Resolving to turn fat into muscle (and not simply to lose weight) motivates you to work on fat-burning aerobic activities and anaerobic muscle-building activities as well. Either way, you are changing your overall body composition from less fat to more muscle. Diet is just as much a part of fitness as exercise, and what you eat will affect every aspect of your workout. A proper diet also influences the results of your fitness plan, since it helps build muscle and decrease the percentage of fat in your overall body weight.