Fast metabolism is the key to efficient and effective fat burning. Lucky are the ones whom mother nature has bestowed with that, so they can sleep peacefully, while others need to purchase an appropriate supplementation. Specimens that raise the level of thyroid hormones - the organ which is the main energy center of the body. Significant is also an increase in testosterone and adrenaline level - the so-called accelerating the nervous system hormones, and thereby also the metabolism. You may also be tempted to use estrogen blockers and cortisol, which will slow down the disintegration of lean muscle mass during the fat burning.