CLA
A fat from dairy and beef, taken mostly for losing body fat.
- Body fat
- Lean muscle
- Exercise and training
A plain-English overview, not advice. Written from published reviews and trials and from what people say in public forums.
On this page
What is CLA?
CLA is short for conjugated linoleic acid, a family of closely related fats that are rearranged versions of linoleic acid, the everyday fat in vegetable oils. It occurs naturally in dairy products, beef and lamb, and only in traces in plants, so the CLA in a capsule is made by converting linoleic acid into its conjugated form, and the oil named on the label is usually safflower. Two of the family do most of the work in the research: the one written c9,t11, which is the main one in food, and the one written t10,c12, which is the one tied to body fat. Supplements carrying it have been promoted for weight reduction for years, and that is what almost everyone buys it for.
Why do people take CLA?
Body fat
The thinking. Losing body fat is what almost everyone buys CLA for. The idea came out of animal work, where one of the two main isomers changed how much fat was stored and how much was burned, and mice on it lost a great deal of fat.
What research has found. Meta-analyses pooling dozens of randomised trials, mostly in adults who were overweight, found small average reductions in weight, fat mass and waist, each under a kilogram or a centimetre or two. The largest and most recent, covering more than four thousand people, found the same small reductions but no fat change once only the best-conducted trials were counted. A fair body of trials has looked at this, and most point the same way.
Lean muscle
The thinking. The other half of the appeal is what people hope CLA leaves alone. Dieting costs lean tissue as well as fat, so something thought to push fat out of storage and into use is taken in the hope that what goes is fat rather than muscle.
What research has found. One randomised trial, in 66 adults with a high body-fat percentage taking about 3 g a day for twelve weeks alongside diet and activity advice, measured muscle by body scan and found more of it in the trunk than in the placebo group. The larger body-composition poolings also report a small average gain in lean mass, though that was not what they set out to measure. Few studies have measured this yet, so there is little to go on either way.
Exercise and training
The thinking. CLA is also sold to people who train. If it changes the way fat is stored and burned, the thinking runs, it might make a block of training go further, either by taking more fat off or by leaving more fuel for working muscle. It is taken alongside a gym routine rather than instead of one.
What research has found. Trials in untrained and moderately trained men taking 3 g to 5.6 g a day for six to eight weeks measured maximal oxygen uptake, time to exhaustion, fatigue thresholds, sit-ups and jumping, and found no difference from placebo. A review pooling twenty trials of CLA with exercise found more body fat lost than with exercise alone, but no gain in performance. Studies here point in different directions, so this one is still being worked out; the dose, how long people took it and who took part all seem to matter.
What does CLA do in the body?
CLA is a fat, and the body handles it like one: it is absorbed with the fat in a meal, carried in the blood and built into tissue. What draws researchers to it is not its use as fuel but the signals it sends about fat, and about how much of it is taken out of the blood and stored rather than broken down and burned.
In more detail, reviewers describe CLA lowering the activity of lipoprotein lipase, the enzyme that pulls fat out of the blood into fat cells, and raising carnitine palmitoyltransferase-1, which ferries fat into the cell’s furnaces. It also acts on PPAR-gamma, a switch controlling how fat cells develop, and on UCP-1, a protein that lets cells burn energy as heat. The two isomers seem to do different jobs, t10,c12 being the one tied to body fat and c9,t11 the one studied for inflammation. Gut bacteria make CLA from linoleic acid too, which is how it is produced commercially.
What do people say about taking CLA?
These are anecdotes people have shared, not evidence.
What people like
- These six threads come from two fitness communities, so the people posting were already training and dieting, and judged CLA on how their middle looked.
- Several described less fat around the middle after a few weeks to a few months, noticed as looser clothes or a flatter stomach.
- A couple felt it worked slightly at ordinary amounts, and one found it easier to keep off weight already lost than to lose more.
- The stubborn spots are what people aimed it at: the belly, the last layer over the abs, and weight left after pregnancy.
- One point in its favour was that it carries no stimulant, so it is taken with meals rather than before a workout.
Common complaints
- The commonest theme by far: nobody could separate CLA from the diet, the training and the other supplements they began at the same time.
- Several stopped: some after months with nothing to show, one over the cost, one over the aftertaste of a version mixed into a protein powder.
- Cost came up repeatedly, described as dear for something whose effect no one could point to with any confidence.
- Nobody in these threads described a side effect from the capsules; the grumbles were about money and about seeing no change.
- One person gave up after looking it up and finding that long-term safety in people had not been settled.
How people take it
- Two to three grams a day is the usual amount described, split across meals rather than swallowed in one go.
- It is taken alongside a calorie-controlled diet and training, and often stacked with other things such as green tea or chromium.
- People give it weeks rather than days: a few weeks to two or three months before deciding whether anything has happened.
- Some argue the ordinary amount is too small to matter and discuss far larger ones, though nobody described actually taking them.
Read from these public discussions:
- Anyone heard of CLA - Conjugated Linoleic Acid? (Cathe Friedrich Fitness Forums, 2003)
- CLA??? (Cathe Friedrich Fitness Forums, 2005)
- CLA anyone??? (Cathe Friedrich Fitness Forums, 2005)
- CLA (Conjugated Linoleic Acid) Use? (Cathe Friedrich Fitness Forums, 2013)
- CLA & Body Fat (T Nation forums, 2002)
- Superhigh Megadosing CLA (T Nation forums, 2008)
What forms of CLA are there?
| Form | What’s different | Per serving, on products we list |
|---|---|---|
| CLA | Usually a roughly equal blend of the two main isomers, carried in safflower oil. | 500 mg to 960 mg |
What else is worth knowing about CLA?
- Trials most often used about 3 g a day, with a range from about 2 g to nearly 7 g, and ran from six weeks to six months. Labels give the amount per serving, which is often two or three capsules, and people in the trials took them split across meals.
- The side effects reported in the longer trials were constipation, diarrhoea and soft stools. Nearly all the trials were in adults who were overweight or obese, or in young men who were training.
- Not every measurement moved in a welcome direction. Two poolings of trials found C-reactive protein, a marker of inflammation, higher with CLA than with placebo, and the largest pooling of blood fats found triglycerides and LDL cholesterol higher, while other reviews found the opposite.
- Liver enzymes and blood sugar are what reviewers say to keep an eye on: one pooling found a small rise in AST, a liver enzyme, and another found higher fasting blood glucose in people at raised cardiovascular risk. Other poolings found no change in either, and reviews list glucose handling, insulin resistance and liver function among the drawbacks reported alongside the benefits.
If you take medication, are pregnant, or have a health condition, check with a pharmacist or GP first.
The research behind this page (24 studies)
- The effects of conjugated linoleic acid supplementation on anthropometrics and body composition indices in adults: a systematic review and dose-response meta-analysis. (2024, meta-analysis)
- 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. (2024, meta-analysis)
- 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. (2019, meta-analysis)
- 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. (2012, meta-analysis)
- Metabolomic Changes Upon Conjugated Linoleic Acid Supplementation and Predictions of Body Composition Responsiveness. (2022, randomised trial)
- 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. (2020, randomised trial)
- The Effect of Conjugated Linoleic Acid Supplementation on Body Composition, Serum Insulin and Leptin in Obese Adults. (2019, randomised trial)
- Twelve weeks CLA supplementation decreases the hip circumference in overweight and obese women. A double-blind, randomized, placebo-controlled trial. (2016, randomised trial)
- Metabolism of c9,t11-conjugated linoleic acid (CLA) in humans. (2013, randomised trial)
- Effects of milk supplementation with conjugated linoleic acid on weight control and body composition in healthy overweight people. (2013, randomised trial)
- Effect of conjugated linoleic acid supplementation on weight loss and body fat composition in a Chinese population. (2012, randomised trial)
- Microencapsulated conjugated linoleic acid associated with hypocaloric diet reduces body fat in sedentary women with metabolic syndrome. (2012, randomised trial)
- Conjugated linoleic acid supplements preserve muscle in high-body-fat adults: A double-blind, randomized, placebo trial. (2020, randomised trial)
- Effects of conjugated linoleic acid and exercise on body composition and obesity: a systematic review and meta-analysis. (2023, meta-analysis)
- Conjugated Linoleic Acid Supplementation has no Impact on Aerobic Capacity of Healthy Young Men. (2015, randomised trial)
- Effects of 6 weeks of aerobic exercise combined with conjugated linoleic acid on the physical working capacity at fatigue threshold. (2014, randomised trial)
- CLA supplementation and aerobic exercise lower blood triacylglycerol, but have no effect on peak oxygen uptake or cardiorespiratory fatigue thresholds. (2014, randomised trial)
- Effects of conjugated linoleic acid supplementation and exercise on post-heparin lipoprotein lipase, butyrylcholinesterase, blood lipid profile and glucose metabolism in young men. (2013, randomised trial)
- Conjugated Linoleic Acid Effects on Cancer, Obesity, and Atherosclerosis: A Review of Pre-Clinical and Human Trials with Current Perspectives. (2019, review)
- Conjugated linoleic acid (CLA) as a functional food: Is it beneficial or not? (2023, review)
- Implication of conjugated linoleic acid (CLA) in human health. (2012, review)
- Modulation of inflammation and immunity by dietary conjugated linoleic acid. (2016, review)
- A review on effects of conjugated linoleic fatty acid (CLA) upon body composition and energetic metabolism. (2015, review)
- Bacterial conjugated linoleic acid production and their applications. (2017, review)
How much does CLA cost?
That depends on the form and the pack, so we work out the price of the same dose of every CLA product we can find and rank them.