CLA (Conjugated Linoleic Acid)
Conjugated linoleic acid (cis-9,trans-11 and trans-10,cis-12 isomers)
TL;DR
CLA supplements (about 3-3.4 g a day) cut body fat by roughly half a kilogram versus placebo in pooled trials: too small to notice. Some trials found worse insulin sensitivity and higher inflammatory markers.
Ideal For
- Healthy adults who want to try it, with modest expectations
- People already following a diet and exercise plan
Avoid If
- Type 2 diabetes, prediabetes or insulin resistance
- Liver disease or a history of supplement-related liver injury
- Children and teenagers
- Pregnancy or breastfeeding
- Heart disease or high cardiovascular risk, without your clinician's advice
Frequently Asked Questions
What is conjugated linoleic acid (CLA)?
Does CLA help you lose weight?
Is CLA safe?
How much CLA should you take?
What foods contain CLA?
Does CLA affect blood sugar?
Overview
Conjugated linoleic acid (CLA) is not one molecule but a family of isomers of linoleic acid, an omega-6 fat. The natural sources are dairy products, beef and lamb, where cis-9,trans-11 is the main isomer. Supplements are usually made from vegetable oils and contain roughly equal amounts of cis-9,trans-11 and trans-10,cis-12, the isomer thought to drive the effect on body fat.
CLA became a weight-loss supplement after it cut body fat sharply in mice. Human results are far smaller. The largest meta-analysis, 70 randomised trials with 4,159 adults (Asbaghi 2024), found an average fat-mass difference of 0.44 kg versus placebo, and the high-quality trials on their own showed no fat loss at all. Most other reviews that judged clinical relevance reached the same verdict: statistically significant, clinically unimportant.
The safety picture is the reason to be careful. In obese men, the trans-10,cis-12 isomer worsened insulin sensitivity and raised markers of oxidative stress and inflammation (Riserus 2002 and 2004). In people with type 2 diabetes, a standard CLA blend raised fasting glucose. One meta-analysis found a small rise in C-reactive protein (another found none), another a small rise in fasting glucose, and there are rare case reports of severe liver injury in people taking CLA weight-loss products.
For weight loss, diet and activity changes, and medicines where appropriate, have far larger effects. CLA is not dangerous for most healthy adults at studied doses, but it offers little and carries signals that matter most for people with diabetes, prediabetes or liver disease.
How It Works
- In animals, the trans-10,cis-12 isomer is the form linked to lower fat gain; the cis-9,trans-11 isomer, the main one in food, has little effect on fat.
- Proposed fat-loss mechanisms include lower food intake, higher energy expenditure, less fat synthesis (lipogenesis) and more fat breakdown and oxidation.
- In cell and animal studies, CLA reduces the formation of new fat cells from precursor cells (preadipocytes).
- In obese men, trans-10,cis-12 CLA raised urinary isoprostanes, a marker of oxidative stress, and the rise tracked worsening insulin resistance.
- The mechanisms come mostly from rodents, where effects on fat are far larger than in people, so they say little about how much CLA can do in humans.
Quick Facts
- Isomers of linoleic acid, an omega-6 fat
- Natural sources: dairy, beef and lamb
- 70-trial meta-analysis: 0.44 kg less fat
- High-quality trials: no fat loss
- Trial doses: about 3.2-3.4 g a day
- Can worsen insulin sensitivity in some people
Benefits & Outcomes
Weight Loss Support
A statistically real but clinically trivial effect on weight and fat, with metabolic safety signals that outweigh it for many people.
Insulin Sensitivity
Conflicting results that lean towards harm in adults: not a supplement to take for blood sugar.
Cholesterol Management
Consistently null for LDL and apolipoprotein B, with small unfavourable shifts in HDL, triglycerides and lipoprotein(a).
Supporting Research38 studies
The effects of conjugated linoleic acid supplementation on anthropometrics and body composition indices in adults: a systematic review and dose-response meta-analysis
Asbaghi O, Shimi G, Hosseini Oskouie F +4 more
small but significant improvement in anthropometric and body composition markers
Conjugated linoleic acid supplementation, insulin sensitivity, and lipoprotein metabolism in patients with type 2 diabetes mellitus
Moloney F, Yeow TP, Mullen A +2 more
CLA supplementation had an adverse effect on insulin and glucose metabolism
Opposing effects of cis-9,trans-11 and trans-10,cis-12 conjugated linoleic acid on blood lipids in healthy humans
Tricon S, Burdge GC, Kew S +4 more
trans-10,cis-12 CLA increases LDL:HDL cholesterol and total:HDL cholesterol
Supplementation with conjugated linoleic acid causes isomer-dependent oxidative stress and elevated C-reactive protein: a potential link to fatty acid-induced insulin resistance
Risérus U, Basu S, Jovinge S +3 more
t10c12 CLA supplementation increases oxidative stress and inflammatory biomarkers in obese men
The effects of conjugated linoleic acid supplementation on lipid profile in adults: A systematic review and dose-response meta-analysis
Asbaghi O, Ashtary-Larky D, Naseri K +4 more
In total, 56 RCTs with 73 effect sizes met the inclusion criteria
Conjugated linoleic acid supplementation for 1 y does not prevent weight or body fat regain
Larsen TM, Toubro S, Gudmundsen O +1 more
does not prevent weight or fat mass regain in a healthy obese population
Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome
Risérus U, Arner P, Brismar K +1 more
t10c12 CLA increased insulin resistance (19%; P < 0.01)
Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans
Whigham LD, Watras AC, Schoeller DA
CLA produces a modest loss in body fat in humans
Milk enriched with conjugated linoleic acid fails to alter blood lipids or body composition in moderately overweight, borderline hyperlipidemic individuals
Venkatramanan S, Joseph SV, Chouinard PY +3 more
consumption of the two CLA-enriched milks failed to alter plasma total cholesterol
The effect of 6 months supplementation with conjugated linoleic acid on insulin resistance in overweight and obese
Syvertsen C, Halse J, Høivik HO +4 more
CLA does not affect glucose metabolism or insulin sensitivity
Conjugated linoleic acid impairs endothelial function
Taylor JS, Williams SR, Rhys R +2 more
worsened endothelial function
Conjugated linoleic acid supplementation for twelve weeks increases lean body mass in obese humans
Steck SE, Chalecki AM, Miller P +4 more
it may also increase markers of inflammation in the short term
Effect of conjugated linoleic acid on blood inflammatory markers: a systematic review and meta-analysis on randomized controlled trials
Haghighatdoost F, Nobakht M Gh BF
CLA supplementation may increase inflammatory markers
The efficacy of long-term conjugated linoleic acid (CLA) supplementation on body composition in overweight and obese individuals: a systematic review and meta-analysis of randomized clinical trials
Onakpoya IJ, Posadzki PP, Watson LK +2 more
the clinical relevance is uncertain
The effects of supplementation with conjugated linoleic acid on anthropometric indices and body composition in overweight and obese subjects: A systematic review and meta-analysis
Namazi N, Irandoost P, Larijani B +1 more
Supplementation with CLA can slightly reduce body weight and FM
Conjugated linoleic acid supplementation for 1 y reduces body fat mass in healthy overweight humans
Gaullier JM, Halse J, Høye K +4 more
reduces BFM in healthy overweight adults
Conjugated linoleic acid supplementation for 8 weeks does not affect body composition, lipid profile, or safety biomarkers in overweight, hyperlipidemic men
Joseph SV, Jacques H, Plourde M +3 more
these results do not confirm a role for CLA
Effect of conjugated linoleic acid on body fat accretion in overweight or obese children
Racine NM, Watras AC, Carrel AL +1 more
decreased HDL more than in the placebo group
Efficacy of dietary supplements containing isolated organic compounds for weight loss: a systematic review and meta-analysis of randomised placebo-controlled trials
Bessell E, Maunder A, Lauche R +3 more
insufficient evidence to recommend any of these dietary supplements for weight loss
Supplementation with trans10cis12-conjugated linoleic acid induces hyperproinsulinaemia in obese men: close association with impaired insulin sensitivity
Risérus U, Vessby B, Arner P +1 more
The use of weight-loss supplements containing this fatty acid is worrying
The effects of conjugated linoleic acid supplementation on glycemic control, adipokines, cytokines, malondialdehyde and liver function enzymes in patients at risk of cardiovascular disease: a GRADE-assessed systematic review and dose-response meta-analysis
Ghodoosi N, Rasaei N, Goudarzi K +4 more
while increasing FBG and AST
Body Fat Changes and Liver Safety in Obese and Overweight Women Supplemented with Conjugated Linoleic Acid: A 12-Week Randomised, Double-Blind, Placebo-Controlled Trial
Mądry E, Malesza IJ, Subramaniapillai M +4 more
CLA supplementation was well tolerated and safe for the liver
The effect of conjugated linoleic acid supplementation in comparison with omega-6 and omega-9 on lipid profile: a graded, dose-response systematic review and meta-analysis of randomized controlled trials
Akhgarjand C, Tavakoli A, Samavat S +4 more
the meta-analysis considered 35 randomized controlled trials (RCTs) with 1,476 participants
Effects of Conjugated Linoleic Acid Intake in the Form of Dietary Supplement or Enriched Food on C-Reactive Protein and Lipoprotein (a) Levels in Humans: A Literature Review and Meta-Analysis
Derakhshandeh-Rishehri SM, Rahbar AR, Ostovar A
The intake of CLA as a dietary supplement led to a significant increase in CRP levels
Conjugated linoleic acid supplementation in humans--metabolic effects
Smedman A, Vessby B
No effects on body weight, serum lipids, glucose metabolism, or PAI-1 were seen
Safety profile of conjugated linoleic acid in a 12-month trial in obese humans
Whigham LD, O'Shea M, Mohede IC +2 more
Laboratory tests showed no adverse effects of CLA
Supplementation with conjugated linoleic acid for 24 months is well tolerated by and reduces body fat mass in healthy, overweight humans
Gaullier JM, Halse J, Høye K +4 more
CLA supplementation for 24 mo in healthy, overweight adults was well tolerated
The effects of conjugated linoleic acid supplementation on cardiovascular risk factors in patients at risk of cardiovascular disease: A GRADE-assessed systematic review and dose-response meta-analysis
Esmaeilnejad M, Rasaei N, Goudarzi K +4 more
CLA seems not to have adverse effects on lipid profiles and blood pressure
The effect of conjugated linoleic acid supplementation after weight loss on body weight regain, body composition, and resting metabolic rate in overweight subjects
Kamphuis MM, Lejeune MP, Saris WH +1 more
it did not result in improved body weight maintenance after weight loss
Effects of conjugated linoleic acid and exercise on body composition and obesity: a systematic review and meta-analysis
Liang CW, Cheng HY, Lee YH +3 more
CLA combined with exercise is generally safe
Comparison of dietary conjugated linoleic acid with safflower oil on body composition in obese postmenopausal women with type 2 diabetes mellitus
Norris LE, Collene AL, Asp ML +4 more
Supplementation with CLA reduced body mass index (BMI) (P = 0.0022)
Conjugated linoleic acid (CLA) reduced abdominal adipose tissue in obese middle-aged men with signs of the metabolic syndrome: a randomised controlled trial
Risérus U, Berglund L, Vessby B
may decrease abdominal fat, without concomitant effects on overall obesity
Fulminant hepatitis during self-medication with conjugated linoleic acid
Nortadas R, Barata J
fulminant hepatic failure requiring liver transplantation
Association of foods enriched in conjugated linoleic acid (CLA) and CLA supplements with lipid profile in human studies: a systematic review and meta-analysis
Derakhshande-Rishehri SM, Mansourian M, Kelishadi R +1 more
favourable effects on LDL cholesterol levels
Conjugated linoleic acid versus high-oleic acid sunflower oil: effects on energy metabolism, glucose tolerance, blood lipids, appetite and body composition in regularly exercising individuals
Lambert EV, Goedecke JH, Bluett K +4 more
there were no CLA-specific effects on body composition, energy expenditure or appetite
Effects of Conjugated Linoleic Acid and Metformin on Insulin Sensitivity in Obese Children: Randomized Clinical Trial
Garibay-Nieto N, Queipo-García G, Alvarez F +4 more
Improvement of insulin sensitivity
Conjugated linoleic acid-induced toxic hepatitis: first case report
Ramos R, Mascarenhas J, Duarte P +2 more
hepatotoxicity due to CLA ingestion
Conjugated Linoleic Acid-induced Hepatotoxicity Requiring Liver Transplant
Saffran NL, Gross AS, Yu AT
conjugated linoleic acid (CLA) toxicity requiring liver transplantation
Safety Information
Potential Side Effects
Mostly digestive: constipation, diarrhoea, soft stools and nausea. In some trials CLA raised C-reactive protein, fasting glucose and liver enzymes (AST) slightly, lowered HDL cholesterol, raised lipoprotein(a), or worsened blood-vessel function (flow-mediated dilation). Rare case reports describe severe liver injury, including liver failure needing a transplant, in people taking CLA weight-loss products.
Contraindications
Avoid with type 2 diabetes, prediabetes or insulin resistance unless your clinician agrees, because CLA worsened glucose control and insulin sensitivity in several trials. Avoid with liver disease. Not recommended for children or during pregnancy or breastfeeding, where its safety has not been established.
Drug Interactions
- Diabetes medicines (metformin, insulin, sulfonylureas, others): CLA raised fasting glucose and reduced insulin sensitivity in a trial in type 2 diabetes, which may work against treatment; check with your prescriber and monitor glucose.
- Other weight-loss supplements and products: reported cases of CLA-related liver injury involved weight-loss products; avoid stacking them, and stop if you notice jaundice, dark urine or itching.
- Cholesterol-lowering treatment: CLA's effects on LDL, HDL and lipoprotein(a) were inconsistent across trials; tell your clinician so your lipid results can be interpreted.
Pregnancy & Breastfeeding
Pregnancy: Not enough evidence to judge
Breastfeeding: Not enough evidence to judge
Dosage Guidelines
Dosage Used in Studies
3-3.4 g
Best Time to Take
No timing has been tested; taking it with meals may reduce stomach upset.
Best Form
Mixed-isomer CLA (about 50:50 c9,t11 and t10,c12), the form used in most trials
Bioavailability
Both the triglyceride and free fatty acid forms lowered body fat versus placebo in a one-year trial, so neither form has a proven advantage.
Dosing by Goal
| Goal | Dose | Notes |
|---|---|---|
| Doses used in fat-loss trials (adults) | 3.2-3.4 g CLA daily | 3.2 g was the median dose in a 2007 meta-analysis; 3.4 g was used in the two-year extension trial. An early meta-analysis estimated about 0.09 kg of fat a week versus placebo for up to 6 months; larger, more recent analyses put the total difference at about 0.4-1.3 kg. |
| Higher doses | 6-6.4 g daily | Subgroup analyses suggest slightly more loss above 3.4 g a day, but at 6.4 g a day one 12-week trial saw higher C-reactive protein, IL-6 and white cell counts and lower HDL cholesterol. |
| Children | Not recommended | One trial in overweight 6-10-year-olds used 3 g a day; it slightly slowed fat gain but lowered HDL cholesterol and bone mineral gain. |
Forms Compared
Mixed-isomer CLA (about 50:50 c9,t11 and t10,c12)
Best for The form behind the meta-analysis results
The standard supplement form and the one used in most trials, usually sold as softgels of oil in which CLA is a share of the total (the children's trial used an 80% CLA oil).
Triglyceride vs free fatty acid CLA
Best for No clear winner
Both forms lowered body fat versus placebo in a one-year trial (Gaullier 2004). Lipid effects differed: LDL rose in the free fatty acid group and HDL fell in the triglyceride group.
Single-isomer trans-10,cis-12 CLA
Best for Not recommended
Studied, not commonly sold. This is the isomer that worsened insulin sensitivity and raised inflammatory and oxidative-stress markers in obese men.
CLA from food (dairy, beef, lamb)
Best for Normal diet; no fat-loss effect expected
Mostly the cis-9,trans-11 isomer, at a few milligrams per gram of fat. Estimated intake in Portugal was about 74 mg a day, around 40 times less than a supplement dose.
Food & Timing
With meals; mild stomach upset, loose stools and constipation were the most common side effects in trials.
Medical Disclaimer
The information provided on this website is for educational and informational purposes only and is not intended as a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or before starting any supplement regimen.
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.