L CARNITINE increases muscle mass, reduces fat mass. Bangkok Hospital Headquarter L Carnitine: Benefits, Side Effects, FAQ, Sources, and Dosage L Carnitine doesn't magically burn fat, it helps your body use fat as energy. Combine it with training and consistency, and you'll feel the difference @Marybosch shows us how L Carnitine will boost your Did You Know? Some people report a fishy smell after supplementing with L carnitine. This happens because certain gut bacteria convert carnitine to trimethylamine, a malodorous compound found in rotting fish.