Mechanisms of body fat modulation by conjugated linoleic acid (CLA)

Since its discovery as an anticancer principal from ground beef extract in the 1980s, conjugated linoleic acid (CLA) has drawn much attention due to its variety of biological activities. One of the most interesting aspects of CLA is its ability to reduce body fat while enhancing lean body mass. One explanation for the variety of biological activities of CLA is that CLA is a mixture of geometric and positional isomers, although the primary research focus is on the two main isomers, cis-9, trans-11 and trans-10, cis-12. The involvement of eicosanoid metabolism has been suggested as one mechanism for CLAs wide range of biological activities. Incorporation of CLA in the sn-2 position of phospholipid fractions, and the negative correlation between tissue levels of CLA and arachidonic acid support this. Other possible mechanisms of CLA with regard to body fat reduction will be discussed, as well as differences between human and animal studies. Safety concerns regarding the use of CLA in humans are not conclusive and need further investigation. (c) 2006 Elsevier Ltd. All rights reserved.