L Carnitine Tartrate Does It Help Burn Fat? AS IT IS Nutrition Trimethylaminuria: Definition, symptoms, and more L Carnitine is not a magic fat burner , It wont melt fat, build muscle, or replace hard work., The only thing it burns is your money , Stick to the basics Nutrition, Training & Consistency. 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.