Neither CLA nor lecithin have any scientific basis to be thought to be fat burners.
Indeed both them are fatty acids, with different structure and some of them binded to some phosphorous. Moreover, CLA isn't a natural fatty acid and our organism has lots of problems to metabolize it, and there are some studies that suggest CLA has carcinogenic effects.
On the other hand, theorically carnitine is effective to decrease body fat levels. Carnitine is needed to start de betaoxidation process, that's the fat-burning process in our cells. But the one that has the key factor is not the carnitine, but the carnitine palmitoyltransferase system (CPT system), that catalizes the binding reaction between carnitine and the fatty acids. The levels of CPT can not neiter be increased nor decreased nowadays, and despite taking a lot of carnitine, if our CPT system is saturated it can not work faster.
In conclusion, this kind of suplements are just wallet-cleaners.
I do agree with:
webinfrontThe three fat burners I have had the most success with are running, swimming and biking.