Within the metabolism (which remember is the sum of all chemical reactions involved in the body), the reactions governing the breakdown and utilization of our food are called catabolic and anabolic. Catabolic reactions break down food into smaller forms while anabolic reactions create larger molecules.
Ideally these catabolic and anabolic reactions exist in a balance. If there is a net positive change (catabolic reactions release more energy than anabolic reactions use), the excess energy will be stored by building fat molecules. Conversely, when there is a negative balance (more is used than generated), excess energy (fat) stores are used to compensate.
Usually, catabolic reactions are about 40% efficient, meaning 40% of energy captured from food is converted to ATP while the rest is released as heat. ATP is the energy currency of the cell and powers all of our bodily functions. Whether we are deriving our energy from carbohydrates, fats, or protein, the end product is always the same. ATP.
Anabolic reactions use some of that ATP to join smaller molecules into larger ones. These reactions form new muscle, tissues, cells, and help keep our organs healthy.
Of the three macronutrient groups (protein, fat, carbohydrate), carbohydrates are the preferred source of energy used to #fuelthebody. Carbohydrates from food are broken down into monosaccharides. Most often, glucose. Excess glucose is stored as glycogen in the muscle and liver or converted to fat in adipose tissue.
Regarding fat, triglycerides are most often used for energy by a process called beta-oxidation. Excess fats tend to be stored either as adipocytes in or around organs or as subcutaneous fat.
Proteins are broken down into their individual amino acids and used for muscle protein synthesis or to create ATP. When other substrates are depleted, muscle protein can be broken down to be used for energy production. Not a good thing.
How to use this information: Feed your brain! Information is powerful. But now that we’re on that topic, our brain uses mostly carbs for fuel. Another reason low carb is for the birds.
Betts, J. G., Young, K. A., Wise, J. A., Johnson, E., Poe, B., Kruse, D. H., … DeSaix, P. (2020, September 20). Anatomy and Physiology. Retrieved from https://openstax.org/books/anatomy-and-physiology/pages/24-1-overview-of-metabolic-reactions