Factors that did in fact enhance performance were genetic endowment, proper training and nutrition, and an adequate supply of fluids and carbohydrates. At the Nestle Research Centre, researchers studied the effect of L-carnitine on exercise metabolism after depletion of muscle glycogen. Nine healthy male subjects received L-carnitine or a placebo and then were submitted to 60 minutes of exercise after an overnight fast. The evidence presented here reports no harmful side effects. Product reports contest that l-carnitine works by transporting fatty acids to be burned for fuel, increasing both energy supply and lean muscle mass.
Studies show a more skeptical look at the product.
Most found that unless an individual is deficient in l-carnitine, it is an unnecessary ergogenic aid. I conclude that as with other vitamins, minerals and medications, L-carnitine is as effective as the consumer's belief in the product. Effect of L-carnitine on submaximal exercise metabolism after depletion of muscle glycogen. A case of secondary L-carnitine deficiency due to anorexia nervosa and severe liver damage. Inhibition of citrate lyase may aid aerobic endurance.