Effectiveness of L-carnitine in Weight Loss: Evidence from Science

Effectiveness of L-carnitine in Weight Loss and Muscle Building

For more than 30 years, manufacturers from the food industry have marketed L-carnitine as a supplement for aiding weight loss and improving exercise performance. While some might consider this as another marketing ploy, these claims have a scientific basis.

The Effectiveness of L-carnitine: Benefits of Supplementation for Weight Loss and Muscle Building

What is L-carnitine? Where Does it Come From?

L-carnitine is a non-essential amino acid that plays a critical role in the metabolism of fatty acids. It specifically acts as a medium for transporting long-chained fatty acids into the mitochondria—the powerhouse of the cell. Once inside the mitochondrial matrix, these fatty acids are broken down through beta-oxidation to acetyl CoA to obtain usable energy via the citric acid cycle.

There are several natural sources of L-carnitine, particularly animal-derived food products such as white and red meat, fish, egg, and milk. But the food industry has manufactured and marketed L-carnitine supplements to capitalize on the possible effects in weight loss and physical performance.

How Does It Aid in Weight Loss? How Does It Work?

An important 2011 study by B. T. Wall et al. revealed that regular oral ingestion of L-carnitine along with carbohydrate consumption could increase muscle carnitine content while also altering muscle fuel metabolism during exercise. These two mechanisms are important for several reasons. First, increasing muscle carnitine level would allow the body to use fat as an energy source instead of glycogen. Second, allowing the body to spare glycogen results in delayed exhaustion, thus allowing extended physical activity. These effects are observed during low-intensity workouts.

Another interesting finding from the study of Wall et al. points to the critical role of L-carnitine supplementation in reducing muscle anaerobic ATP production that, in turn, results in reduced lactic acid accumulation during high-intensity workouts. This translates to reduced muscle soreness, shorter recovery time, and better exercise performance.

In summary, the aforementioned study has demonstrated the dual role of L-carnitine: glycogen sparing during low-intensity workouts and reduced lactic acid accumulation due to high-intensity workouts.

There are more takeaways from the study of Wall et al. Results revealed that L-carnitine supplementation during the first three months had no effect, particularly in increasing muscle carnitine content. But after six months, muscle carnitine content increased by 21 percent. Hence, to fully exploit the benefits of L-carnitine supplements, individuals must take them for an extended period.

Another study by Kalpana and Aruna revealed that L-carnitine supplementation could help in the weight management of overweight and obese adults. But the weight loss effect of L-carnitine is only achievable if accompanied by regular and routinized exercise.

A Note on Supplementation and Physical Activity

L-carnitine supplementation can help in weight loss only if accompanied by physical activity or physical fitness training, particularly a workout routine. Supplementation not only promotes the use of fat as an energy source but also improves the physical performance of individuals while also increasing the efficiency of the body in using energy. It is also essential to note that the effects of L-carnitine have clinical importance in the treatment or management of type 2 diabetes and other metabolic diseases.

It is also worth mentioning that other studies were carried out to investigate the effects of L-carnitine supplementation in weight loss and physical performance. Some of these studies contradicted the claims noted above. However, as mentioned in the review of K. Sahlin, the study of Well et al. remains ground-breaking because it investigated the effects of long-term L-carnitine supplementation, thus explaining the difficulties and failures in previous studies with shorter supplementation periods.


  • Kalpana, A. 2012. “Effects of L-Carnitine (Neutraceutical) In Weight Management Among Overweight and Obese Adults of Age Between 20-45 Years–A Comparative Study in Chennai and Tirupathi.” International Journal of Scientific and Research Publications. 2(9)
  • Sahlin, K. 2011. “Boosting Fat Burning with Carnitine: An Old Friend Comes Out from the Shadow.” The Journal of Physiology. 589(P7): 1509-1510. DOI: 1113/jphysiol.2011.205815
  • Wall, B. T., Stephens, F. B., Constantin-Teodosiu, D., Marimuthu, K., Macdonald, I. A., and Greenhaff, P. L. 2011. “Chronic Oral Ingestion of L-carnitine and Carbohydrate Increases Muscle Carnitine Content and Alters Muscle Fuel Metabolism During Exercise in Humans.” The Journal of Physiology. 589(4): 963-973. DOI: 1113/jphysiol.2010.201343