01/22/2025
1. Fat storage and breakdown
Fats in foods ingested by the body are broken down during digestion into fatty acids and glycerol, which enter the bloodstream and are transported throughout the body. The excess fatty acids are synthesized into triglycerides (triglycerides) in the liver and fat cells and then stored. When we consume too many calories, the body stores this excess fat as adipose tissue for use during peak energy demands.
Storage: When food is eaten, fats are digested in the intestines and fatty acids and glycerol enter the bloodstream. They are transported through the bloodstream to adipose tissue where they become triglycerides and are stored in fat cells. This process is controlled by hormones such as insulin, which prompts fat cells to combine fatty acids and glycerol to form triglycerides and store them.
Catabolism: Fat stores are mobilized when the body needs energy (e.g., during exercise, or when hungry). Hormones, such as adrenaline and noradrenaline, activate lipolytic enzymes in fat cells that begin to break down stored triglycerides into fatty acids and glycerol.
2. Fatty acid release and transportation
Broken down fatty acids travel through the bloodstream to the liver, muscles, and other tissues that use fatty acids as a source of energy. Fatty acids can be transported to where they are needed for energy via fatty acid transfer proteins (FABP) and plasma proteins such as albumin.
Muscle: During exercise, muscle cells have a large demand for energy, especially during aerobic exercise, and fat becomes an important source of energy. Fatty acids enter the muscle cell and are broken down into carbon dioxide and water through the process of “beta-oxidation” in the mitochondria, which also releases ATP (cellular energy).
Liver: Fatty acids also enter the liver, where liver cells convert them through fatty acid oxidation into ketone bodies, which serve as a source of energy for the brain and other tissues, especially during prolonged periods of starvation or on low-carbohydrate diets such as the ketogenic diet.
3. β-oxidation (process of fatty acid oxidation)
In cells, fatty acids enter the mitochondria and undergo β-oxidation, which is the primary catabolic process of fatty acids. Each oxidation process removes two carbon atoms to create an acetyl-coenzyme A (acetyl-CoA). These acetyl-coenzyme A molecules enter the tricarboxylic acid cycle (also known as the Krebs cycle) and ultimately pass through the respiratory chain to produce ATP. this process is the central step in the energy-providing process for fats.
4. Ketone body production and utilization
When the body experiences prolonged starvation or low carbohydrate intake, the liver converts fatty acids into ketone bodies. Ketone bodies (including acetoacetic acid, beta-hydroxybutyric acid, and acetone) are a highly efficient source of energy, especially for the brain. Normally, the brain relies primarily on glucose, but in times of starvation, it uses ketone bodies as an alternative energy source.
5. Regulation of fat metabolism
Fat metabolism is regulated by a variety of hormones and enzymes. Here are a few key regulators:
Insulin: Insulin is the main storage hormone in fat metabolism. When blood glucose levels are high, insulin secretion increases, promoting fat storage. Insulin inhibits lipolysis and helps store energy as fat.
Epinephrine and norepinephrine: These hormones are released in response to stress, exercise, or hunger and promote the breakdown of fats and release fatty acids into the bloodstream.
Growth Hormone: This hormone is important during childhood growth, it also helps in the breakdown of fat and promotes the release of fatty acids.
Testosterone and estrogen: S*x hormones also have an effect on fat distribution and metabolism. For example, testosterone contributes to fat loss, while estrogen may promote fat storage in certain areas, such as the thighs and buttocks.
