L-carnitine
L-carnitine is an amino acid involved in the burning of FFA for energy (28). Previous
chapters have detailed how the carnitine palmityl transferase-1 system is intimately involved in
ketone body formation and fat oxidation in the muscle. Because of its role in fat oxidation, many
authors have suggested that supplemental L-carnitine might hasten fat loss. While this makes
sense from a theoretical standpoint, most studies have not shown the expected results (28).
Additionally, supplementation of L-carnitine under conditions of glycogen depletion, when it would
be expected to have the greatest impact (since fat oxidation is at its highest), shows no benefit
(29). Considering the high cost of L-carnitine, its use is not recommended.
Pyruvate
Supplemental pyruvate is a new supplement which has entered the fat burner market.
Studies have shown that pyruvate slightly enhances fat loss on very low calorie diet (30,31).
However, the doses necessary, 30 or more grams per day, to achieve this fat loss are cost
prohibitive. Additionally, since commercially available pyruvate supplements typically contain
half their weight as sodium or calcium, the risk for overload exists. Finally, pyruvate can inhibit
ketosis. Pyruvate supplements are not recommended.
Conclusion
There are a number of supplements which may be beneficial to hasten fat loss, spare
muscle loss, and blunt appetite while on a diet. These include the combination of ephedrine,
caffeine and aspirin ; yohimbe ; as well as a variety of fiber supplements that can be used while
dieting. Additionally, there are at least two popular ‘fat burning’ supplements, L-carnitine and
pyruvate, which are not recommended.
References cited
- “Textbook of Medical Physiology” Arthur C. Guyton. W.B. Saunders Company 1996.
- Lafontan M and Berlan M. Fat cell alpha-2 adrenoreceptors: The regulation of fat cell function
and lipolysis. Endocrine Rev (1995) 16: 716-738. - Lafontan M and Berlan M. Evidence for the alpha-2 nature of the alpha-adrenergic receptor
inhibiting lipolysis in human fat cells. Eur J Pharmacology (1980) 66: 87-93. - Wahrenberg H et. al. Adrenergic regulation of lipolysis in human fat cells during exercise. Eur J
Clin Invest (1991) 21: 534-541. - Wahrenberg, H et. al. Mechanisms underlying regional differences in lipolysis in human adipose
tissue. J Clin Invest (1989) 84: 458-467. - Arner P. Adrenergic receptor function in fat cells. Am J Clin Nutr (1992) 55: 228S-236S.
- Strosberg AD. Structure and function of the b3-adrenergic receptor. Annu Rev Pharmacol