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Limited evidenceWeight management

CLA (Conjugated Linoleic Acid)

CLA reduces fat mass by roughly 0.1 kg per week in pooled trials — a trivially small effect that fades after about six months. More importantly, the trans-10,cis-12 isomer that drives fat loss also worsens insulin sensitivity and inflammatory markers, which makes the risk-benefit unfavourable.

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What the science says

  • Very small reduction in fat mass Moderate evidence

    A meta-analysis of 18 randomized trials found CLA at about 3.2 g/day reduced fat mass by roughly 0.09 kg per week versus placebo, with the effect plateauing around six months. That is under 2 kg over a year of continuous supplementation, at doses that cause GI side effects in many users.

  • Impairs insulin sensitivity Moderate evidence

    A randomized trial in abdominally obese men found that purified trans-10,cis-12 CLA induced hyperproinsulinemia and reduced insulin sensitivity compared with placebo and with a CLA isomer mixture. Several other trials report increases in inflammatory markers, oxidative stress and lipoprotein(a). This is the main reason to be cautious with CLA in anyone with metabolic syndrome or prediabetes.

  • Preserves lean mass or improves body composition in athletes Limited evidence

    Effects on fat-free mass in pooled human data are minimal and not consistently significant. There is no credible evidence that CLA enhances strength, hypertrophy or athletic performance in humans, despite persistent marketing to that effect.

Dosage & safety

Studied doseTrials typically used 3.0-6.8 g/day of a 50:50 mixture of the cis-9,trans-11 and trans-10,cis-12 isomers, for 6-24 months. Given the modest benefit and metabolic downsides, there is no dose we would positively recommend.
SafetyGI side effects (nausea, loose stools, dyspepsia) are common at typical doses. The trans-10,cis-12 isomer is associated with insulin resistance, raised inflammatory and oxidative stress markers, and lower HDL. Multiple case reports link high-dose CLA to hepatitis and elevated liver enzymes, with resolution on withdrawal — stop immediately if you develop jaundice, dark urine or right upper quadrant pain. Avoid in people with diabetes, prediabetes, metabolic syndrome, or existing liver disease. Not recommended in pregnancy or lactation (it reduces milk fat content).

How to take it

TimingTiming does not matter; split across meals.
With food?With meals, which reduces the nausea and dyspepsia.
Worth knowingStop immediately and get liver enzymes checked at any sign of jaundice, dark urine or right upper quadrant pain — the hepatitis case reports resolved on withdrawal.

Interactions

With medications

  • insulin, metformin and other antidiabetic medication

    The trans-10,cis-12 isomer is associated with worsened insulin resistance, working against your diabetes treatment. avoid it if you have diabetes, prediabetes or metabolic syndrome

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does CLA help you lose fat?

Barely: a meta-analysis of 18 trials found CLA at about 3.2 g/day reduced fat mass by roughly 0.09 kg per week, under 2 kg over a year, with the effect plateauing around six months. CLA's overall evidence grade is limited given how small the effect is.

Is CLA safe to take?

CLA carries real downsides: the trans-10,cis-12 isomer reduced insulin sensitivity in a trial of abdominally obese men and is linked to raised inflammatory markers and lower HDL. Case reports also link high-dose CLA to hepatitis, so stop if you notice jaundice or dark urine, and avoid it with diabetes, prediabetes, metabolic syndrome or liver disease.

Does CLA help build muscle or improve performance?

No: pooled human data show minimal and inconsistent effects of CLA on lean mass, and there is no credible evidence it improves strength, muscle growth or athletic performance.

What dose of CLA is used in studies?

CLA trials typically used 3.0-6.8 g/day of a 50:50 isomer mixture for 6-24 months. Given the trivial fat loss and metabolic downsides, supp.science does not positively recommend any dose.

Scientific references

Where to buy

NatureWise, CLA , 180 Softgels

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