Amazon.com: Benevolent L Carnitine Supplement High Potency 1500mg L Carnitine Tartrate Fast Absorbing, Convert Fat to Energy, Support Lean Muscle, Boost Workout Performance & Metabolism 120 Vegan Capsules : Health & Household Acute L Carnitine Supplementation Does Not Improve CrossFit Performance: A Randomized, Double Blind, Placebo Controlled Crossover Study Carnitine: the claims and why it may not work Early research into L carnitine was often cited as underwhelming, showing negligible changes in muscle carnitine content and fat loss outcomes. However, these findings may have been limited by a short study window