Amino Acids and Energy Metabolism: An Overview

Abstract The nutrients that provide necessary energy to the body are primarily carbohydrates and lipids. Proteins can also provide energy at 4 kcal/g; however the main roles of proteins are to serve as a source of amino acids and to provide constituent materials to the body. The use of proteins or amino acids as energy is limited to situations in which the intake of carbohydrates or lipids is insufficient to supply necessary energy. Thus, in the context of starvation or when energy intake is insufficient, some ingested proteins or body proteins are used as an energy source. However, body proteins do not have a form for energy storage, such as glycogen for carbohydrates and triglycerides (triacylglycerol) for lipids. Therefore, amino acids, which are obtained mainly by partial degradation of muscle proteins, are used as a source of energy.