# L-Carnitine's Fat-Burner Reputation Lacks Support in Trials

_Evidence Level: Moderate · Eryiğit H et al., International journal of sport nutrition and exercise metabolism, DOI 10.1123/ijsnem.2026-0077_

*Acute and Chronic L-Carnitine Supplementation Enhances Endurance Performance Without Consistent Effects on Substrate Oxidation in Active Individuals: A Systematic Review.*

- **Evidence Level**: Moderate
- **Why this grade**: Review of 18 trials where chance decided who got L-carnitine or a dummy pill; none of the trials was rated at low risk of bias.
- **Facts**: Design: Systematic review
- **Publication Types**: Journal Article
- **Journal**: International journal of sport nutrition and exercise metabolism
- **Sample Size**: 18 studies
- **Authors**: Eryiğit H, Güzel Y, Bulut S, Turnagöl HH, Atakan MM
- **Graded and published**: 2026-10-15
- **Last edited**: 2026-10-21
- **Topics**: Supplements, Exercise
- **DOI**: https://doi.org/10.1123/ijsnem.2026-0077
- **Original Source**: https://pubmed.ncbi.nlm.nih.gov/42887880/

## Summary

L-carnitine has a reputation in sport as a fat burner. A review of 18 studies in active people found no support for that. None of the studies that measured it reported a clear change in how much fat the body burned during exercise. Some measures of endurance, however, were better with the supplement.

In all 18 studies, participants were chosen at random to take L-carnitine or a dummy pill. Ten studies tested a single dose of 2 to 15 grams. Seven tested 2 to 3 grams a day for 2 to 24 weeks, and one tested both. Fat burning showed no clear change, whether people took a dose shortly before exercise or for a few weeks.

The authors conclude that L-carnitine may improve selected endurance outcomes. Still, no study was rated at low risk of bias, and three were rated high risk. The fat-burning data also cover only short use of four weeks at most.

## Practical Takeaway

Across 18 trials, L-carnitine did not clearly increase fat burning during exercise, though some endurance measures improved.

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_Canonical: https://longevity-germany.com/en/research/l-carnitine-s-fat-burner-reputation-lacks-support-in-trials · Part of Longevity Cities · Updated 2026-10-21_