fat metabolism
all the biochemical processes involved in the breakdown, manufacture, or storage of fat in the body. Excess dietary carbohydrates (in the form of glucose) can be converted to fat (in the form of glycerides) and stored in specialized adipose tissue at sites distributed around the body. Excess dietary fat is also stored in this way. Following a meal, uptake of glucose into fat cells (adipocytes) and manufacture of fat are promoted by the hormone insulin. Mobilization of fat occurs during fasting, exercise, and in response to stress and is triggered by the hormone epinephrine and by norepinephrine released by nerve endings of the sympathetic nervous system. Stored fat is mobilized by being broken down to its constituents—fatty acids and glycerol—which are released into the bloodstream to provide fuel for other tissues, especially liver and muscle. Here, the fatty acids are converted into the energy carrier
ATP by means of beta oxidation. However, fatty acids cannot be converted (at least in appreciable amounts) into glucose, which is the fuel required by the brain.