L-carnitine

What it is

L-carnitine helps shuttle fatty acids into cells to be burned for energy. That real biological role is the basis for its long-standing reputation as a "fat-burner" — a reputation that runs well ahead of the evidence.

What the evidence shows

Fat loss. Marketing claim· human data Its role in fat metabolism doesn't translate into meaningful weight loss from a supplement in most people. As a weight-loss aid the evidence is weak.

Recovery and blood flow. Preliminary· human data The more interesting, still-preliminary data is around exercise recovery, with some studies reporting reduced markers of muscle damage rather than fat loss.

Who it suits

There is little compelling case for most healthy, meat-eating people, who already have plenty of carnitine and make their own. Any potential upside is in recovery, not fat loss.

Practical notes

Because deficiency is uncommon in people who eat meat, topping up rarely does much. If fat loss is the goal, an energy deficit, adequate protein and training do the heavy lifting — a supplement can't substitute for those.

Sources

PubMed: L-carnitine supplementation, fat metabolism, weight loss and exercise recovery (reviews and trials)

Frequently asked questions

Does L-carnitine burn fat?

Its role in shuttling fatty acids into cells to be burned is real biology, but that doesn't translate into meaningful fat loss from a supplement in most people. As a weight-loss aid the evidence is weak and often overstated.

Is there anything it may help with?

The more interesting, still-preliminary evidence is around exercise recovery and blood flow rather than fat loss, with some studies suggesting reduced markers of muscle damage. Promising, not proven.

Do I need to supplement it?

Healthy people who eat meat generally have plenty of carnitine and make their own, so a deficiency is uncommon. That's another reason topping up rarely does much.