What Is Fat Metabolism?

Fat metabolism encompasses an array of chemical processes involved in fat storage and utilization. The relative activity of fat metabolism processes varies, depending on your energy status and needs. When you have a surplus of dietary calories, fat metabolism favors storage processes. Fat breakdown dominates when your body needs energy. A healthy diet without an overabundance of calories helps keep your fat metabolism balanced.

Fat Anabolism

Anabolism is the storage side of fat metabolism. Your liver is the first stop for dietary fats absorbed from your digestive system. Fats are processed, packed into protein envelopes and released into your bloodstream. Dietary fats other than cholesterol are processed into triglycerides, also known as triacylglycerols. Each triglyceride molecule has a chemical backbone, glycerol, with three fatty acids attached. Your fat cells, or adipocytes, take up triglycerides and store them until energy is needed.
If you consume more sugar than your body needs, your liver diverts the excess sugar into the fatty acid production pathway. Through this mechanism, excess dietary sugar is converted into triglycerides, packaged and transported to your fat cells for storage.

Storage Sites

Fat is your body's primary storage depot for excess energy. Fat, or adipose tissue, is distributed throughout your body, primarily under your skin. Fat can also accumulate inside your abdomen and can infiltrate your organs. This form of fat, called visceral fat, increases your risk for heart disease and type 2 diabetes.

Fat Catabolism

When your body needs energy, sugar is the first fuel used. If available sugar is insufficient to meet your energy requirements, your fat cells break down stored triglycerides, liberating fatty acids. Cellular powerhouses called mitochondria metabolize fatty acids to yield energy.
When your body burns fat, chemicals called ketones are common byproducts. Ketones can serve as fuel for your brain when your sugar supply is low. High levels of ketones associated with a diabetic crisis, or diabetic ketoacidosis, can be potentially life threatening.

Hormonal Control

Hormones control the rate and balance of your fat metabolism. The pancreatic hormone insulin is the primary promoter of fat anabolism. Glucagon, also produced in your pancreas, has the opposite effect and promotes fat breakdown. The adrenal hormone epinephrine also triggers fat catabolism.

Beyond Energy Storage

Fat has other functions beyond energy production and storage. Adipose tissue is an insulator and aids in maintaining your body temperature. Your fat cells also produce the hormone leptin, an important regulator of hunger. Adipose tissue production of chemicals called cytokines assists your immune system. Excess cytokines, however, might contribute to the development of heart disease and type 2 diabetes. Harmful cytokine production usually occurs with excess visceral fat.