Conjugated linoleic acid (CLA) is the group of linoleic acid isomers that have the conjugated double bonds (as opposed to the isolated double bonds of the conventional linoleic acid) — the most biologically active and most studied CLA isomers are the cis-9, trans-11 CLA (which is the most abundant isomer in the dairy fat and the beef) and the trans-10, cis-12 CLA (which is the most abundant isomer in the supplements and which is primarily responsible for the body composition effects). The CLA has been studied extensively for its effects on the body composition — it reduces the body fat (by inducing the apoptosis of the adipocytes, by increasing the lipolysis, and by reducing the lipogenesis), it increases the lean mass (by stimulating the protein synthesis and by reducing the protein degradation), and it improves the metabolic health (by reducing the insulin resistance, by improving the lipid profile, and by reducing the inflammatory markers). The CLA is found in the dairy fat (particularly in the butter, the cheese, and the full-fat dairy) and in the meat of the ruminants (beef, lamb, goat) — the typical dietary CLA intake from these sources is 100-500mg daily, and the therapeutic doses for the body composition effects are 3-6g daily of the mixed CLA isomers (containing approximately equal amounts of the cis-9, trans-11 and the trans-10, cis-12 isomers). The CLA deficiency is therefore common in people who follow the vegan diet (which is very low in CLA because the CLA is almost exclusively found in the ruminant dairy and meat), and it may contribute to the increased body fat, the reduced lean mass, and the metabolic dysfunction that are associated with the vegan diet unless the CLA is supplemented.
CLA and the Adipocyte Metabolism
The CLA reduces the body fat through multiple mechanisms — it induces the apoptosis of the mature adipocytes (by activating the caspase enzymes and by increasing the ceramide synthesis), it increases the lipolysis (by activating the hormone-sensitive lipase and by inhibiting the perilipin, the protein that coats the lipid droplet in the adipocyte), and it reduces the lipogenesis (by inhibiting the lipoprotein lipase and by reducing the glucose uptake by the adipocytes). The trans-10, cis-12 CLA isomer is primarily responsible for these effects on the adipocyte metabolism — it activates the AMPK (the master regulator of the cellular energy metabolism), it reduces the expression of the adipogenic genes (including the PPAR-gamma and the C/EBP-alpha), and it promotes the browning of the white adipose tissue (by increasing the expression of the uncoupling protein 1, UCP1, which is the protein that is responsible for the thermogenesis in the brown fat). This CLA-induced reduction in the adipocyte lipid storage and the increase in the thermogenesis are the primary mechanisms of the body fat reduction that is associated with the CLA supplementation.
The clinical importance of the CLA for the body composition is underscored by the observation that the CLA supplementation reduces the body fat and increases the lean mass in people with the overweight and the obesity. A meta-analysis of 18 RCTs in over 1000 participants found that the CLA supplementation at 3-4g daily significantly reduced the body fat (by 0.5-1.0kg, or approximately 0.5-1.0% of the body weight) and increased the lean mass (by 0.3-0.5kg) — making the CLA one of the most studied and most effective natural compounds for the body composition improvement. However, the effect size is modest (approximately 0.1kg of fat loss per week), and the CLA should be combined with the calorie restriction and the exercise for the optimal body composition results.
Practical Application
For general CLA supplementation for the body composition improvement, the evidence-based approach is to supplement with 3-6g of CLA daily (as the mixed isomer form that contains approximately equal amounts of the cis-9, trans-11 and the trans-10, cis-12 isomers). The CLA should be taken in divided doses (1.5-3g per dose) with the meals (to enhance the absorption and to reduce the gastrointestinal side effects). The CLA is generally well-tolerated with no significant adverse effects at doses up to 6g daily, though it may cause the gastrointestinal symptoms (nausea, diarrhoea) in some individuals. For comprehensive body composition and metabolic support, CLA pairs well with the omega-3 fatty acids (which have complementary effects on the body composition and on the inflammatory status), with the L-carnitine (which is required for the fatty acid oxidation and which works synergistically with the CLA for the fat loss), with the chromium (which is an insulin-sensitising mineral that helps to direct the nutrients to the muscle rather than to the fat), and with the protein (which provides the amino acids for the lean mass synthesis and which enhances the satiety).
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