L Carnitine, Mixed Berry, 12 fl oz (360 ml) L Carnitine vs Fat Burner Which Is For You? The Marathon L Carnitine helps the body turn fat into energy. If your plan is to use this supplement to optimize energy during your workout, it's best to take it prior to L Carnitine doesnt magically burn fat, it helps your body use fat as energy. Combine it with training and consistency, and youll feel the difference @Marybosch shows us how L Carnitine will boost