CLA (conjugated linoleic acid)

What is it? CLA stands for conjugated linoleic acid and is a derivative of one of the essential fatty acids known as linoleic acid. CLA is unusual in that it's only really found in significant quantities in animal products such as cheese, milk and meat. CLA actually refers to a group of biologically active compounds (called isomers). The most active CLA compound is the 9-cis, 11-trans isomer and this is the main isomer used in scientific trials of CLA.

How does it work? Advocates claim that supplementing CLA in doses of around 3-4 grams a day promotes fat loss in both animals and humans. However, the mechanism is poorly understood.

How strong is the evidence that it works? Unclear. Much of the early research clearly demonstrated fat loss in animal studies, and three quite recent large double blind studies carried out in Scandinavia demonstrated a loss in body fat in humans supplemented with CLA combined with a slight increase in lean body mass. However, other studies have produced far less clear-cut results; it seems that benefits of CLA may not be quite as strong in humans as in those early animal studies.