MEDIUM-CHAIN FATTY-ACID METABOLISM AND ENERGY-EXPENDITURE - OBESITY TREATMENT IMPLICATIONS

Fatty acids undergo different metabolic fates depending on their chain length and degree of saturation. The purpose of this review is to exa mine the metabolic handling of medium chain fatty acids (MCFA) with sp ecific reference to intermediary metabolism and postprandial and total energy expenditure. The metabolic discrimination between varying fatt y acids begins in the GI tract, with MCFA being absorbed more efficien tly than long chain fatty acids (LFCA). Subsequently, MCFA are transpo rted in the portal blood directly to the liver, unlike LCFA which are incorporated into chylomicrons and transported through lymph. These st ructure based differences continue through the processes of fat utiliz ation; MCFA enter the mitochondria independently of the carnitine tran sport system and undergo preferential oxidation. Variations in ketogen ic and lipogenic capacity also exist. Such metabolic discrimination is supported by data in animals and humans showing increases in postpran dial energy expenditure after short term feeding with MCFA. In long te rm MCFA feeding in animals, weight accretion has been attenuated. Thes e differences in metabolic handling of MCFA versus LCFA are considered with the conclusion that MCFA hold potential as weight loss agents.