NutriDex

The Supplement Research Compendium
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CLA

Conjugated Linoleic Acid

Popular fat-loss fatty acid whose real-world effect is tiny.

Mixed evidence 🫀Heart & Metabolic

✚ Updated · How we grade evidence

Evidence tier
Mixed
Research weight
Citations
8 verified / 8
Classification
Heart & Metabolic
❝
What the evidence says. Graded mixed: meta-analyses do find statistically significant fat loss, but the magnitude is trivial (~0.7 kg weight, ~1.3 kg fat over months) and vanishes in high-quality studies, while the t10,c12 isomel can worsen insulin resistance and oxidative stress. (Mixed evidence: Conflicting results across studies; benefit uncertain.)

What is CLA?

CLA (Conjugated Linoleic Acid) is a heart and metabolic supplement used for marketed for fat loss. NutriDex grades the human evidence as Mixed. CLA is a group of linoleic-acid isomers found naturally in dairy and beef and sold as a fat-loss supplement, usually as a roughly 50:50 mix of the cis-9,trans-11 and trans-10,cis-12 forms. Pooled randomized trials do show a real but tiny effect: roughly 0.5–0.9 kg less body weight and about 1.3 kg less fat versus placebo over several months. A 2024 dose-response meta-analysis found fat mass fell only ~0.44 kg, and the effect on fat mass and body-fat percentage disappeared when analysis was limited to high-quality trials. Meta-analyses show no benefit on cholesterol, blood pressure, or HbA1c, and some report a small rise in fasting glucose. The trans-10,cis-12 isomer specifically has been shown to raise insulin resistance and oxidative-stress markers in men with metabolic syndrome. Overall the weight benefit is too small to matter clinically, and the metabolic signals are a genuine concern.

Purported Benefits

✓Marketed for fat loss
✓Slight body-fat reduction
✓Body-recomposition claims

Evidence by outcome

The same supplement can be well-proven for one use and unproven for another — here is the human evidence graded outcome by outcome.

OutcomeEvidenceEffectStudies
Body fat / weight lossMeta-analyses show a real but tiny loss (~0.4-1.3 kg fat) that vanishes in high-quality trials; not clinically meaningful. Mixed ↔ mixed · negligible 4
Lipids and blood pressureGRADE meta-analysis in cardiovascular-risk patients found no effect on lipids or blood pressure. Moderate — no effect · negligible 1
Insulin sensitivity / glycemic controlMultiple RCTs show CLA (esp. t10,c12) raises insulin resistance and fasting glucose in obese/diabetic men. Moderate ⚠ risk · moderate 3
Oxidative stress / inflammationRCTs in metabolic-syndrome men report isomer-specific rises in lipid-peroxidation markers and C-reactive protein. Preliminary ⚠ risk · moderate 2

Dosing & Compounds

Typical Dose
Trials use 3.2–6.4 g/day of a ~50:50 c9,t11/t10,c12 isomer mix, taken with meals.
Active Compounds
cis-9,trans-11 (rumenic acid)trans-10,cis-12 isomer

Safety & Cautions

Common side effects are GI: nausea, loose stools, diarrhea and indigestion. The trans-10,cis-12 isomer can worsen insulin resistance, raise fasting glucose, lower HDL and increase oxidative-stress and inflammatory markers, so caution is warranted in diabetes, prediabetes and metabolic syndrome, and CLA may oppose antidiabetic medication. Rare reports of liver injury exist; avoid in liver disease and stop for jaundice or dark urine. Safety in pregnancy and breastfeeding is not established. Educational only — always check with your doctor or pharmacist before combining CLA with any medicine.

Key Studies

Meta-analysis Asbaghi 2024 ✓ PubMed
Dose-response meta-analysis: fat mass −0.44 kg, body-fat −0.77%; effect on fat mass/BFP lost in high-quality trials.
Meta-analysis Esmaeilnejad 2024 ✓ PubMed
GRADE meta-analysis in cardiovascular-risk patients: weight −0.72 kg, body-fat −1.32%, but no effect on lipids or blood pressure.
Meta-analysis Onakpoya 2012 ✓ PubMed
Meta-analysis of 7 RCTs (≥6 months): weight −0.70 kg, fat −1.33 kg vs placebo; deemed not clinically relevant long term.
Meta-analysis Whigham 2007 ✓ PubMed
Meta-analysis: 3.2 g/day CLA produced a modest body-fat loss (~0.09 kg/week) vs placebo in humans.
RCT Riserus 2002 ✓ PubMed
12-wk RCT: trans-10,cis-12 CLA raised insulin resistance 19%, glycemia 4%, and cut HDL 4% in obese men with metabolic syndrome.
RCT Riserus 2002 (Circulation) ✓ PubMed
RCT: t10,c12 CLA caused isomer-specific oxidative stress and raised C-reactive protein in men with metabolic syndrome.
RCT Moloney 2004 ✓ PubMed
RCT in type 2 diabetes: CLA raised fasting glucose 6.3% and lowered insulin sensitivity; raised HDL 8% but not recommended therapeutically.
RCT Riserus 2004 (AJCN) ✓ PubMed
RCT: even the c9,t11 isomer lowered insulin sensitivity 15% and raised lipid-peroxidation markers ~50% in obese men.
8 sources cited · 8 verified Search all studies on PubMed ↗

Common questions about CLA

What is CLA used for?

CLA is most often taken for Marketed for fat loss, Slight body-fat reduction, Body-recomposition claims. Popular fat-loss fatty acid whose real-world effect is tiny.

Does CLA work — what does the evidence say?

Mixed evidence. Conflicting results across studies; benefit uncertain. CLA is a group of linoleic-acid isomers found naturally in dairy and beef and sold as a fat-loss supplement, usually as a roughly 50:50 mix of the cis-9,trans-11 and trans-10,cis-12 forms. Pooled randomized trials do show a real but tiny effect: roughly 0.5–0.9 kg less body weight and about 1.3 kg less fat versus placebo over several months. A 2024 dose-response meta-analysis found fat mass fell only ~0.44 kg, and the effect on fat mass and body-fat percentage disappeared when analysis was limited to high-quality trials. Meta-analyses show no benefit on cholesterol, blood pressure, or HbA1c, and some report a small rise in fasting glucose. The trans-10,cis-12 isomer specifically has been shown to raise insulin resistance and oxidative-stress markers in men with metabolic syndrome. Overall the weight benefit is too small to matter clinically, and the metabolic signals are a genuine concern.

What is the typical dose of CLA?

Trials use 3.2–6.4 g/day of a ~50:50 c9,t11/t10,c12 isomer mix, taken with meals.

Is CLA safe? Any cautions or side effects?

Common side effects are GI: nausea, loose stools, diarrhea and indigestion. The trans-10,cis-12 isomer can worsen insulin resistance, raise fasting glucose, lower HDL and increase oxidative-stress and inflammatory markers, so caution is warranted in diabetes, prediabetes and metabolic syndrome, and CLA may oppose antidiabetic medication. Rare reports of liver injury exist; avoid in liver disease and stop for jaundice or dark urine. Safety in pregnancy and breastfeeding is not established.

How many studies support CLA?

NutriDex cites 8 sources for CLA, graded "Mixed".

Cite this page
APA

Peh, D. (2026). CLA (Conjugated Linoleic Acid): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 26 Jun 2026, from https://nutridex.info/s/cla

BibTeX
@misc{nutridex_cla,
  author       = {Peh, Daryl},
  title        = {CLA (Conjugated Linoleic Acid): Benefits, Dosage, Side Effects \& Evidence},
  year         = {2026},
  howpublished = {NutriDex --- The Supplement Research Compendium},
  url          = {https://nutridex.info/s/cla},
  note         = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-06-26}
}

For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.

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