This study looks at the research behind L-Carnitine (Amazon) to see if it works or not. L-Carnitine promises to convert body fat into energy for your body, so that is what we will verify. Read on to see the results.
Study 1: Fat Oxidation Increased 22%
This study showed that slightly overweight subjects supplementing with 3g of L-Carnitine per day for 10 days increased fat oxidation by 22%. This is clearly positive evidence for its efficacy, but shows that you have to take a fair amount of it to see results. 3g per day is 3 or 6 pills, depending on the strength of your pills. For a good product like Now Foods 1000mg L-Carnitine it is 3 pills per day for a cost of almost $1 per day. $1 per day for a 22% increase in fat oxidation seems like a fair price to me, with no unrealistic claims or expectations.
Study 2: No Improvements Reported
This study had overweight women take 4g of L-Carnitine per day for 8 weeks and did 30 minutes of walking 4 days per week. The group who took L-Carnitine and walked didn’t lose more fat or weight than the group who only walked. This study casts doubt on the efficacy of L-Carnitine. Also some L-Carnitine taking participants reported negative side effects including nausea and diarrhea.
Study 3: Reduced Muscle Breakdown from Exercise
Taking 2g L-Carnitine for 3 weeks resulted in a 50%+ reduction in muscle disruption (ruptured cells) after squatting. This improves recovery time and reduces muscle soreness after exercise. 
Study 4: No Improvements Reported in Male Bodybuilders
12 male bodybuilders took either 1g of L-Carnitine daily or a placebo for 60 days. No differences were reported between the two groups.
Out of 4 studies, 2 showed benefits and 2 showed no changes, so the efficacy of L-Carnitine is questionable. If you can get it cheaply, it may be worth trying, but it is not a magic bullet.
- The effect of l-carnitine on fat oxidation, protein turnover, and body composition in slightly overweight subjects. Klaus D. Wutzke, Henrik Lorenz [↩]
- L-Carnitine supplementation combined with aerobic training does not promote weight loss in moderately obese women. Villani, R. G.; Gannon, J.; Self, M.; Rich, P. A. [↩]
- L-Carnitine L-tartrate supplementation favorably affects markers of recovery from exercise stress. Volek JS, Kraemer WJ, Rubin MR, Gómez AL, Ratamess NA, Gaynor P. [↩]
- The Effect of L-Carnitine Supplementation on Lean Body Mass in Male Amateur Body Builders. R.E. Green, MS, RD, A.M. Levine, PhD, RD, M.J. Gunning, EdD, L.S. Walsh, MS [↩]