Training effectively by using enough weight to sufficiently overload a muscle, micro trauma and micro tears are created in the muscle. The muscle then goes about repairing itself, and to do so the body uses many resources to make this rebuilding a reality. One of the resources it uses is the body's own natural human growth hormone.
Human growth hormone must access stored body fat to help repair the muscle. So making stronger muscles uses fat!!! It may take many strength training sessions, before you add one pound of pure muscle to your body. Nutrition, training, recuperation and stress levels all play a part in the process. If you eat excessively, your blood sugar will remain elevated and sabotage your efforts, so nutrition is truly an important component for success.