Core body temperature fluctuates within a narrow range due to inherent thermoregulatory control. Anesthetics impair thermostatic mechanisms, which leads to hypothermia during surgical procedures. Hypothermia that arises during surgery is associated with postoperative complications, and it can be prevented by delivering intravenous solutions, containing amino acids, that have a higher thermic effect than other macronutrients. Recent studies using anesthetized rats have determined that infusion of intravenous amino acids increases plasma insulin concentrations under anesthesia much more than while conscious, and stimulates skeletal muscle protein synthesis via the insulin-mTOR pathway. The increases in insulin levels, under anesthesia, contribute to amino acid-induced elevations in skeletal muscle protein synthesis, energy metabolism and core body temperature. Amino acid infusions also elevate protein breakdown in skeletal muscle; and the resultant increase in muscular protein turnover is positively involved in the modification of core body temperature. These collateral results indicate that amino acids play a unique role in the control of core body temperature, which is a vital sign that is closely indicative of changes in physical status.