The uncoupling proteins are now known to be mitochondrial inner membrane proteins. Recently, more than five family members have been identified including UCP1,UCP2,UCP3,UCP4 and UCP5 in the mitochondrial inner membrane of different tissues and organs of species, such as in human, mammals, poultry, fish and even in plants. UCPs regulate the energy metabolism, increase the fatty acids oxidation and the UCPs polymorphism are related to fat metabolism.