“Fat burners.” At this point, you have probably turned a skeptical eye towards, well, all of them. Hopefully we have helped you understand a little more about the essential roles both diet and exercise play in weight management. Sometimes, though, the manufacturers get tricky, turning a kernel of truth into a giant popcorn bowl of false promises.
Carnitine is one such case. Sellers of supplemental carnitine do not- and legally cannot- explicitly say that taking carnitine will help you lose weight or better your athletic performance. But they can imply as much by saying that carnitine is a “natural fat-burning nutrient” and “metabolic accelerator” that “facilitates the metabolism of long-chain fatty acids” and “may improve fat metabolism during exercise.”
How do they claim this? Here’s the kernel of truth: carnitine, a protein produced naturally in the human body, does play an important role in the metabolism of fat. After fatty acids enter your cells, they need to enter the mitochondria (where fat burning takes place), but larger fatty acids can’t cross the mitochondria’s membrane alone. In effect, carnitine is the shuttle bus that transports fat into the mitochondria, allowing fat oxidation to proceed.
This fact is used by supplement marketers to claim that oral carnitine supplements increase overall fat burning and improves athletic endurance by allowing your muscles to burn more stored fat for energy. That may sound good, but unfortunately, science has yet to show either an athletic or a weight-loss benefit from orally supplementing carnitine.
There are a few limited studies out there at best, and almost all of them show that although blood concentrations of carnitine may increase from an oral dose, this carnitine never actually reaches the muscles, where about 95% of your body’s carnitine resides and is really needed to do its work. As you might then expect, oral carnitine has also yet to show any impact on muscle glycogen stores or athletic performance.
Carnitine supplements? Until evidence proves otherwise, put them in the wallet burner category and don’t bother.