Adipose (fat) cells play several critical roles in systemic metabolism and physiology. There are at least two classes of fat cells—white and brown. White fat is specialized to store energy in the form of triglycerides, an especially efficient method because this class of molecules is highly energetic and stored anhydrously. On fasting, the release of fatty acids and glycerol to provide fuel for the rest of the body occurs via enzymatic hydrolysis called lipolysis. These crucial functions of fat, storage, and release of fatty acids are tightly controlled by the key hormones of the fed and fasted states—insulin and catecholamines.
