The Effect of BCAA on Health and Meal Pattern Amino acids, the building blocks of proteins, have been intensively studied to determine their effect on metabolism, food intake, appetite and tissue synthesis. Despite the satiating effect of proteins, Branched Chain Amino Acids (BCAA), Isoleucine, Leucine and Valine have been used in the clinical setting as a catabolic agent to prevent anorexia and cachexia in critical illness. It also prevents protein- energy malnutrition in patients suffering from liver cirrhosis. Moreover, BCAA supplementation is popular among athletes to increase muscle mass, to provide energy for muscles and to delay central fatigue. The mechanism(s) responsible for hyperphagic and catabolic effects of BCAA is yet unclear. BCAA bypass the liver to be metabolized in the muscle, limiting the amount of hepatic ATP produced, which inhibits orexigenic hormones. On The other hand, BCAA could limit the production of the satiating hormone, serotonin in the Central Nervous System (CNS). This book explains the effect of each BCAA on metabolism, appetite, and tissue composition.