“Muscle mass comprises between 30 and 50 percent of your body’s total weight — the more the better. Composed of more than 650 muscles, it is the primary user of calories in the active human body, and the storage facility for most of the body’s protein. Muscles are the motors which move the skeleton — the system of levers we use to interact with our environment — and are therefore responsible for our physical relationship with our surroundings.
Fat, on the other hand, is where calories are stored, not used. Mostly, fat just lays there, using very few calories itself but hoping you’ll use the calories it stores as fuel for muscle contraction. In great quantities, the few hormones produced in adipose tissue may become metabolically significant, and in great quantities adipose tissue can become the host of significant amounts of inflammation.”