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L-Carnitine for Weight Loss

Can It Help You Lose Weight?

By

Updated June 02, 2014

Written or reviewed by a board-certified physician. See About.com's Medical Review Board.

Overweight girl looking at underweight reflection
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L-carnitine is a nutrient widely available in supplement form and often marketed as a weight loss aid. Made naturally in the body, L-carnitine is essential for transporting fat into cells to produce energy.

While many supplement manufacturers claim that L-carnitine can speed up metabolism, there is little scientific support for L-carnitine's ability to promote weight loss.

Health Benefits of L-Carnitine for Weight Loss

To date, few clinical trials have tested l-carnitine's effectiveness as a weight loss aid. The available research includes a 2000 study from the International Journal of Sport Nutrition and Exercise Metabolism, in which 36 moderately overweight premenopausal women were given either L-carnitine or a placebo twice daily for eight weeks. Analyzing study results, researchers found no difference in total body mass or fat mass between those who took L-carnitine and those given the placebo.

A number of animal studies have also shown that L-carnitine may not support weight loss. A 2002 study from the Annals of Nutrition and Metabolism, for instance, found that rats treated with l-carnitine did not experience a greater reduction in body fat levels compared to a control group.

What's more, a 2005 study published in the International Journal for Vitamin and Nutrition Research found that rats fed an L-carnitine-enhanced diet tended to gain more weight than other animals in the study (despite no difference in their intake of calories).

Side Effects

In some cases, L-carnitine supplements may produce certain side effects (including nausea, abdominal cramps, diarrhea, and a "fishy" body odor). In addition, L-carnitine may interact with antibiotics used in the long-term prevention of urinary tract infections (such as pivampicillin).

Sources:

Brandsch C, Eder K. "Effect of L-carnitine on weight loss and body composition of rats fed a hypocaloric diet." Ann Nutr Metab. 2002;46(5):205-10.

Melton SA, Keenan MJ, Stanciu CE, Hegsted M, Zablah-Pimentel EM, O'Neil CE, Gaynor P, Schaffhauser A, Owen K, Prisby RD, LaMotte LL, Fernandez JM. "L-carnitine supplementation does not promote weight loss in ovariectomized rats despite endurance exercise." Int J Vitam Nutr Res. 2005 Mar;75(2):156-60.

Office of Dietary Supplements. "Dietary Supplement Fact Sheet: Carnitine". Last accessed February 2011.

Villani RG, Gannon J, Self M, Rich PA. "L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women." Int J Sport Nutr Exerc Metab. 2000 Jun;10(2):199-207.

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