Outcome
    Moderate Evidence

    L-Carnitine for Thermogenic Effect

    Carnitine helps only where levels are low; muscle stores are hard to raise by supplementing.

    Overview

    Carnitine helps only where levels are low; muscle stores are hard to raise by supplementing.

    Verdict

    Insufficient evidence

    How It Works

    Transports long-chain fatty acids into mitochondria for beta-oxidation.

    Dosing & Protocol

    Typical dose

    Recommended dose
    2g/day with carbohydrate
    Expected timeframe
    12-24 weeks

    Protocol

    form
    Not applicable
    duration
    Not applicable
    co factor
    Evidence is insufficient. Carnitine is marketed as a fat burner on the basis that it transports fatty acids into mitochondria, but transporting a substrate is not the same as increasing metabolic rate. Human trials measuring energy expenditure, resting metabolic rate or thermogenesis after carnitine supplementation at 2-4 g/day have not shown meaningful increases, and the compounds that do produce measurable thermogenesis - caffeine, ephedrine, capsaicinoids, high-dose green tea catechins - work through sympathetic and uncoupling mechanisms that carnitine does not engage. The one carefully controlled loading study that raised muscle carnitine over 24 weeks found altered fuel selection rather than increased total energy expenditure. Carnitine may appear in thermogenic blends but is not the reason those blends have any effect.
    titration
    Not applicable
    starting dose
    Not applicable as an established thermogenic

    Evidence

    What the studies say

    Meta-analyses show small weight reductions, largely in obese or older populations. Muscle carnitine content barely changes without co-ingested carbohydrate and insulin.

    No studies are yet linked to both L-Carnitine and Thermogenic Effect.

    Safety

    Caveats

    Raises TMAO, a marker associated with cardiovascular risk. Small effect sizes.

    Less likely to help if

    Everyone: no thermogenic effect has been demonstrated in humans.

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    Individual results may vary. The statements on this website have not been evaluated by the Food and Drug Administration. Products and information are not intended to diagnose, treat, cure, or prevent any disease.