The constructive phase of metabolism in which the body builds complex molecules from simpler building blocks, consuming energy to create order. After a protein-rich meal, anabolism assembles amino acids into muscle and enzymes; after carbohydrate intake, it strings glucose into glycogen stores; and throughout growth and repair, it synthesizes the tissues that maintain the body. Insulin is its master signal, rising after eating to switch cells from breakdown to building. Anabolism dominates during childhood growth, pregnancy, and recovery from injury, when the demand for new tissue is highest. Athletes and clinicians manipulate it deliberately through training, feeding, and sometimes medication. Paired with its opposite, catabolism, it forms the continuous cycle of renewal by which the body maintains itself against entropy.