Can l-carnitine supplementation be useful for people trying to lose body fat? The verdict is still out according to one literature review published in 2017.

L-carnitine is an amino acid derivative that is both consumed through food and synthesized by the body.  L-carnitine helps in the disposal of glucose during periods of hyperinsulinemia, assists with glycogen storage, assists with fatty acid metabolism and glucose disposal.  This is how L-carnitine improves glucose tolerance, especially in patients with type 2 diabetes.

In one study, L-carnitine prevented insulin spikes in healthy patients after the consumption of a glucose solution.   In another study, L-carnitine improved glucose disposal and storage in both healthy subjects and subjects with T2DM.  The efficacy of l-carnitine in assisting with glucose and insulin management seems well established.

Well, what about fat loss?

Supplementation with L-carnitine prevented body fat increases in subjects consuming a high carbohydrate diet, but it didn’t necessarily assist with fat loss.  Instead, it helped with glucose uptake into skeletal muscle.  This tells me that l-carnitine is likely an excellent choice for people consuming a caloric surplus to gain muscle mass. Still, it may not be that useful for people who want to lose body fat during a caloric deficit.

If a person is insulin-resistant, there is a chance that l-carnitine might be useful, but that is theoretical thinking and has not been proven according to the research presented in the literature review cited here.

Even still, is supplementation necessary for these benefits? It’s possible.  It may be beneficial if you are prone to l-carnitine deficiency.

The following groups are at a higher risk of l-carnitine (hypocarnitinemia) deficiency and may benefit from l-carnitine supplementation:

• vegans/vegetarians
• people following a ketogenic diet
• people who are consuming a caloric deficit while participating in vigorous exercise
• people with anorexia or bulimia
• people on dialysis
• people taking certain medications regularly (antibiotics, antivirals, anticonvulsants, PPIs)

What is well-established is that physical activity, especially high-intensity activity, increases l-carnitine synthesis by the body.  So, if you want the benefits of l-carnitine, and you’re not prone to l-carnitine deficiency, you could simply rely on exercise to help you out and save yourself some money.

Reference

Adeva‐Andany, M.M., Calvo‐Castro, I., Fernández‐Fernández, C., Donapetry‐García, C., Pedre‐Piñeiro, A.M. (2017). Significance of l‐carnitine for human health. IUBMB Life, 69, 578-594.