Energy is a fundamental need of a living cell, which runs various reactions in an organism, generates signaling mediators, and regulates homeostasis. Energy is produced and consumed in specific metabolic pathways known as anabolism and catabolism. The former is the process of building complex molecules, while the latter is the breakdown of these molecules to produce energy in the form of adenosine triphosphate (ATP).
Protein synthesis is one of the essential anabolic pathways activated by insulin and mTOR signaling. Conversely, catabolism results in the breakdown of proteins to ensure that energy-producing cycles have materials for generating ATP. These two phenomena are adequately balanced in an organism when food intake and energy expenditure are equal, but the equilibrium may shift in case of overconsumption or food scarcity.