Conjugated Linoleic Acid (CLA)
CLA has been shown to be a highly effective supplement to aid in weight loss and in the conversion of fat to lean muscle mass. To achieve this, CLA causes enhanced insulin sensitivity so that fatty acids and glucose can pass through muscle cell membranes and away from fat tissue. This results in an improved muscle to fat ratio. CLA is used by body builders to drive glucose into muscle cells to produce anabolic effects. Dieters use this same sugar burning mechanism to prevent serum glucose from turning into body fat.

CLA also has antioxidant properties, and has been shown to prevent muscle wasting (an anti-catabolic effect).

CLA is chemically related to linoleic acid, but appears to have opposite effects in certain important areas. For instance, linoleic acid stimulates fat formation (lipogenesis) in adipose tissue, while CLA inhibits fat formation (involving Lipoprotein Lipase); linoleic acid tends to promote tumour growth, while CLA is an excellent inhibitor of tumour growth (anti-cancer); linoleic acid makes cholesterol more susceptible to oxidation, while CLA makes cholesterol more stable.

CLA is found in red meat and cheese and displays strong anti-cancer properties; particularly effective in inhibiting breast and prostate tumours, as well as stomach and skin cancer.

As stated above, the most promising science around CLA concerns its effect on weight management. Thirty-five intervention studies have been conducted using CLA in humans to investigate the effects of CLA on weight management. These studies, which vary widely in CLA dose and duration, show the most significant effect of CLA on weight management is on body composition, a reduction in total body fat and an increase in lean body mass. The effect of CLA on fat mass is modest and at the recommended dosage of 3.2 g/day produces a statistically significant 90 g fat loss per week (about 1 lb in 5 wk) as shown by a 2007 meta-analysis. Doses higher than the recommended 3.2g do not seem to have any additional effects on body fat reduction. Another meta-analysis found that CLA supplementation produces about 1% increased growth in targeted lean body mass per week. With the simultaneous decrease in fat mass coupled with increases in lean body mass, often the net change in weight is small. However, the effects of CLA on body composition is a healthy effect, since the degree of fat mass is related to many causes of mortality and lean body mass burns more calories than fat mass, which may help to increase resting metabolic rates. CLA use itself is not an answer to the prevalence of obesity, but it can be a useful tool in addition to a healthy lifestyle and exercise program to achieve and maintain a healthy body weight.
Some studies have found no significant effects of CLA supplementation on fat mass loss.

Clarinol® brand of CLA is the best available CLA supplement due to their rigorous quality control procedures which produce the highest possible concentration of beneficial active CLA fatty acids, which are c-9, t-11 and t-10, c12 as shown below