Contrary to popular belief, carnitine (sometimes referred to as l-carnitine) is not an amino acid but a quaternary amine, which the body manufactures out of two amino acids—lysine and methionine. It is found naturally in such food sources as red meat, fish and dairy products.
Carnitine plays many important roles in the body, but the most important one from a fat burning perspective is its role in escorting fatty acids to the cell’s mitochondria (think of the mitochondria as the cell’s furnace) where they can be burned as fuel. Because Carnitine plays such a role, many have postulated that supplementation should aid in weight loss.
However, studies to date have been largely contradictory, and there does not seem to be any real evidence showing that supplementing with carnitine will lead to dramatic weight loss.
One study (Int J Sport Nutr Exerc Metab. 2000 Jun;10(2):199-207) performed on 36 moderately overweight premenopausal women concluded…
“Eight weeks of L-C ingestion and walking did not significantly alter the TBM (total body mass) or FM (fat mnss) of overweight women, thereby casting doubt on the efficacy of L-C supplementation for weight loss.”
Another one (see Metabolism. 2004 Aug;53(8):1002-6) found that supplementing with 3 grams of l-carnitine daily led to a significant increase in fat oxidation.
Regardless of this conflicting data, it’s important to note that most fat burners touting the fat burning abilities of carnitine usually only contain only a spattering of this compound.
Most studies have been completed using 2-6 grams daily. Any less than this is simply “label dressing” (it looks good on the label, but there’s nowhere near enough of the compound to elicit any effect).
If you want to experiment with l-carnitine for the purpose of weight loss, you’ll need to take a hefty dose. BodyBuilding.com sells the NOW brand of liquid l-carnitine, and you’ll need to take a minimum of two tablespoons daily—and doubling this dose would probably be a smart idea.
Regardless of its weight loss effects, carnitine is a very exciting compound for another reason; it seems to be invaluable for heart health, helping to prevent, even reverse ischemia, stabilize irregular heartbeats, reduce incidents of angina, lower triglycerides and maintain a beneficial cholesterol profile (see clinical study abstracts here, here, and here as relevant examples).
At this point, carnitine’s heart-health benefits might well be the most compelling reason to consider using this product.