Facts about the fat burners - The classic: L-carnitine

Probably the most advertised substance for accelerating fat loss for quite some time is L-carnitine. It is often referred to directly as a "fat burner" and recommended for body weight reduction. But does it also do what is promised?

The intake of L-carnitine can be done in tablet form or as a liquid. Many manufacturers also enrich food with this substance and then sell it as so-called "functional food". These include bars or drinks and recently even gummy bears with L-carnitine. In your body, this substance occurs mainly in the red skeletal muscle. That's why meat is also a good source of carnitine. In contrast, vegetable foods contain only small amounts.

What is carnitine doing in your organism?

Carnitine is an endogenous substance that can be produced in your liver, kidney and brain. If you were not feeding carnitine, your body will be able to synthesize it from the two amino acids methionine and lysine. This endogenous carnitine production does not make carnitine one of the essential nutrients1. This means that it does not need to be externally supplied to maintain the function of your organism. The production rate is about 15 mg per day while another 10-70 mg are taken through the diet. 98% of your carnitine reserves are in your skeletal and cardiac muscles. The remaining 2% in the liver and the kidney, about the daily 20 mg carnitine are excreted through the urine. In your muscle cell carnitine acts as a transport molecule, because it ensures that the long-chain fatty acids from the fatty tissue and from the muscle tissue reach the mitochondria. There, they are then burned through the process of so-called beta oxidation to produce energy in the form of ATP1.

By taking more fat is not burned!

Since carnitine is not consumed in the muscle cell, it is always available on demand as a means of transport. Even the small amounts that your body loses through the urine are more than compensated by food intake and biosynthesis. In addition, your organism stores larger amounts. Precisely for this reason, in a healthy person there is neither a lack of carnitine nor a consumption or loss that would have to be compensated. Even with endurance-trained competitive athletes there is always enough carnitine in the muscle cell. Other important points are that dietary supplements do not get carnitine into the muscle cell2. If the intake is subject to saturation, the "more" carnitine is indeed collected in the blood plasma and then excreted through the urine, but it does not reach the muscle cell. If the substance does not even reach the site of action, the first questions arise regarding the effectiveness of the additionally ingested carnitine2.

L-carnitine is just a means of transport

Even if you could increase the concentration of carnitine in the muscle cell by taking a shot, this would not be synonymous with increased fat burning. The availability of the transport molecule is not the limiting factor in fat oxidation. This is rather determined by the enzyme activity of the involved degradation pathways. This so-called lipolysis rate is a process that runs independently of the carnitine concentration. The decisive factor is how many free fatty acids can be mobilized during muscle work and how many mitochondria exist with the corresponding enzymes in the muscle cell. However, this effect can only be influenced by endurance training and not by the supplementation of a transport vehicle. If you want to clarify these processes, perhaps the following example helps: Carnitine is an airplane and the free fatty acids are the guests. The mitochondria are the airline that wants to make a profit with the guests. The provision of many fliers is of no use if not enough guests book a flight. Ultimately, the number of guests determines the profit and not the number of means of transport.