How CLA works?
Scientific research has revealed that CLA isomers have the ability to bind to and activate the Peroxisome Proliferator activated Receptor alpha (PPARa) which is highly expressed in the liver and the c9t11 isomer has the strongest binding affinity on that receptor followed by t10c12 and then other CLAs. Interesting to note that c9t11 CLA is around 8-fold more potent than linoleic acid (nonconjugated form) at inducing PPARa. Basically, this activation increases fat burning in the liver.
CLA has also been demonstrated to inhibit PPARy. PPARy is a receptor that is found in fat cells and moderates fat cell proliferation and accumulation of triglycerides. The t10c12 form of CLA was observed to inhibit the y receptor and c9t11 was observed to activate the y receptor. It turns out that genetic variations in the y receptor are associated with variations in genetic response to CLA supplementation in humans.
Basically CLA isomers are known as PPAR modulators that are able to activate PPARa located mostly in the liver. Depending on the isomer they can activate or inhibit PPARy in fat cells that are involved in fat regulation.
Furthermore, CLA is known to increase energy expenditure by way of increases in a Carnitine enzyme and Acyl-CoA oxidase. All of this has been linked to the t10c12 isomer. The enzyme Fatty Acid Synthase (FAS) interacts with CLA but studies are unclear as to whether there is a decrease in enzymatic activity meaning fat burning increases so further research needs to done here. Protein changes in the body are due to modulations of the a and y receptors by CLA as well. It is also noted that glycerol is released from fat cells indicating an increase in fat release from triglycerides and hence fat burning.
Put in simple terms, CLA decreases body fat mass and increases lean muscle mass. CLA accumulates in tissues of animals and humans where it is readily metabolized. It is possible that CLA may trigger fat cell death, shrink fat cells or speed up metabolism to generate weight loss. The CLA mechanism is complex and not completely understood at this time. Nevertheless, CLA can act as an appetite suppressant making you eat less (fewer calories in) while increasing the rate of fat burning (increase calories out) and inhibiting the production of fat.
CLA in Supplements
It is important to know that the CLA that is in supplements is not derived from natural foods. The supplement companies make it by chemically altering safflower and sunflower oils which you should know are unhealthy vegetable oils. These botanicals are high in linoleic acid and this acid is converted into the conjugated linoleic acids by way of a chemical process known as alkali isomerization. The balance of the different isomer forms can be heavily distorted in supplements. Foods mostly have the c9t11 isomer while supplements are high in the t10c12 isomer which is never found in large amounts in nature. Make sure to buy a high-end CLA that contains the two most biologically active forms.