In 30 seconds
- CLA reviews are divided because its effects are modest and slow: in trials of 6 months or longer, 1.3 kg less fat than with placebo.
- Anyone judging it on the scales after two weeks notices nothing: the shortest trials with a result lasted 4 and 12 weeks, and the effect grew up to 6 months.
- Anyone taking it with a calorie deficit, protein and strength training notices more, because what measures the results is the whole plan, not the softgel.
- What the trials do describe are mild digestive complaints. EFSA considers 3-3.5 g a day for 6 months to be safe.
CLA reviews range from “it worked really well for me” to “it does nothing”, and both can be true. Placebo-controlled trials say something more useful: CLA has a modest, slow effect on fat, of 0.09 kg per week with 3.2 g a day 1 and 1.3 kg over 6 months or longer 2. Anyone measuring it on the scales after a fortnight notices nothing; anyone measuring it with a tape measure after three months does. Here is what the studies say and how to judge your own results.
Why the reviews are divided
Four reasons explain almost every review you will read:
- Time. Studies measure CLA in weeks and months. The shortest trial with a result lasted 4 weeks 4, and in the reference meta-analysis the effect grew up to 6 months 1. Two weeks is not enough to judge it.
- The measure. In trials of 6 months or longer, weight fell 0.7 kg and fat 1.3 kg 2. The scales show less than the waist does.
- The plan. CLA does not replace a calorie deficit. Anyone taking it without changing anything expects too much; anyone adding it to diet, protein and strength training notices it as part of a whole.
- Expectations. It is not a stimulant: it gives no energy or heat and does not raise your pulse. Anyone expecting to feel it does not.
What the trials measured
CLA versus placebo, in figures
What the trials measured, and when
| Duration | Study | What was seen versus baseline or placebo |
|---|---|---|
| 4 weeks | 25 men with abdominal obesity, 4.2 g a day | Smaller abdominal diameter than with placebo |
| 12 weeks | 63 adults, 3.4 g a day | 0.69 kg less weight and 0.49 kg less fat from baseline |
| Up to 6 months | Meta-analysis of 18 trials, 3.2 g a day | 0.09 kg less fat per week; the effect grew up to 6 months |
| 6 months or longer | Meta-analysis of 7 trials | 0.7 kg less weight and 1.3 kg less fat than with placebo |
| 1 year | 180 overweight adults, 3.4-3.6 g a day | Between 6.9 and 8.7% less fat mass than with placebo |
Results of the studies cited in the text. In all of them, participants kept their usual diet and activity.
The two meta-analyses agree on the direction and size of the effect. Whigham's pooled 18 trials and calculated 0.09 kg of fat per week with 3.2 g a day, with more effect at higher doses 1. Onakpoya's kept only the studies of 6 months or longer, in people who were overweight or obese, and found 0.7 kg less weight and 1.3 kg less fat than with placebo; its authors describe the effect as small 2. We go through them study by study in CLA research: trials, dose and safety.
One finding is worth keeping in mind: in the one-year trial, participants changed neither their diet nor their exercise, and their fat mass was still 6.9 to 8.7% lower than with placebo 3. And another explains many negative reviews: in an 8-week trial of 28 young women with obesity, 3.2 g a day alongside aerobic exercise did not reduce fat more than placebo 5. Eight weeks and a small sample: exactly the scenario in which CLA does not show.
What people say and what the studies say
| What people often say | What the studies say |
|---|---|
| “I noticed nothing in two weeks” | Normal: the shortest trial with a result lasted 4 weeks, and the effect grew up to 6 months |
| “The scales did not move” | Over 6 months or longer, weight fell 0.7 kg and fat 1.3 kg: the scales show less than a tape measure |
| “My waist changed” | The only trial focused on the abdomen measured a smaller abdominal diameter with 4.2 g a day for 4 weeks |
| “It upset my stomach” | In the long trials, constipation, diarrhoea or loose stools were described; it is taken with meals |
| “I felt no energy” | CLA is not a stimulant: it contains no caffeine and you do not feel it when you take it |
Common phrases from forums and shops, set against the results of the trials cited.
How to measure your results
Four measures that show more than the scales
How to measure your results
If you are going to take CLA, decide beforehand how you will judge it. We suggest four measures, every 4 weeks, always at the same time of day and before eating:
- Waist, at navel height, without pulling tight. It is the measure closest to what the abdomen trial measured 4.
- Skinfolds, if you have a calliper: abdomen, hip and thigh. We explain it in skinfold testing in football.
- Photos, with the same light, the same time and the same posture. They are for you, not as proof of what CLA does: photos cannot separate the supplement from the diet.
- Strength: if you hold or increase your loads while your waist shrinks, you are losing fat, not muscle.
The scales, once a week and as secondary data. We tell you what to expect each month in how long CLA takes to work.
Who notices it most, and who least
The trials give some clues. The effect grew with the dose 1 and with time 1, and the long studies were done in people who were overweight or obese 2: if you start from a high body-fat percentage, there is more room. In women, a 6-month trial measured 1.3 kg less fat than with placebo; you have it in CLA for women: studies, dose and effects.
Those who notice it least take it irregularly, stop after three weeks or have no calorie deficit. And nobody notices it as energy: that is what stimulants are for, and we compare them in fat burners: which ones work, according to the studies.
The side effects that come up in reviews
Negative reviews about tolerance usually mention the stomach, and the trials confirm it: in the long studies, constipation, diarrhoea or loose stools were described 2, and it is generally well tolerated 5. Taking it with meals, one softgel with each, is the way to avoid it. EFSA considers 3-3.5 g a day for 6 months to be safe 6.
If you have diabetes, are pregnant or breastfeeding, or take medication, check with your doctor first. You have the full picture in CLA side effects and who should not take it.
How to take it so you can judge it on data
- Dose: 2.4-3.5 g of CLA a day, the range used in the trials and by EFSA 1 6. Look at the milligrams of CLA, not of oil.
- When: with meals, every day, without breaks.
- How long: 12 weeks at a minimum to judge it; up to 6 months.
- With what: a moderate calorie deficit and strength training. If you train, L-carnitine 30 minutes before is the usual partner; we compare them in CLA vs L-carnitine.
The full answer, with dose and timing, is in what CLA is good for: dose, timing and what the studies say.
Frequently asked questions
Does CLA actually work?
In placebo-controlled trials there is a difference, but a modest one: 0.09 kg more fat lost per week with 3.2 g a day, and 1.3 kg more fat in studies of 6 months or longer. The result depends on having a calorie deficit and taking it for months, not days.
Why are CLA reviews so different?
Because its effects are slow and small, and everyone judges it by a different yardstick: the scales after two weeks, the waist after three months, or energy, which CLA does not give because it is not a stimulant.
What results can you expect from CLA in 3 months?
If there is a calorie deficit, the diet does the fat loss; according to the reference meta-analysis, CLA adds around 0.09 kg of fat per week, that is, about 1 kg over 12 weeks. You see it in the tape measure and skinfolds, less so on the scales.
Are CLA before-and-after photos reliable?
Photos cannot separate what CLA does from what diet and training do. What is reliable are the placebo-controlled trials: with CLA, fat mass was 6.9 to 8.7% lower than with placebo after a year.
Does CLA get bad reviews because of side effects?
What the long trials describe are mild digestive complaints: constipation, diarrhoea or loose stools. EFSA considers 3-3.5 g a day for 6 months to be safe. If you have diabetes, are pregnant or take medication, check with your doctor.
Sources
- Whigham LD, Watras AC, Schoeller DA. Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. Am J Clin Nutr. 2007;85(5):1203-1211. View publication
- Onakpoya IJ, Posadzki PP, Watson LK, Davies LA, Ernst E. 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. Eur J Nutr. 2012;51(2):127-134. View publication
- Gaullier JM, Halse J, Høye K, et al. Conjugated linoleic acid supplementation for 1 y reduces body fat mass in healthy overweight humans. Am J Clin Nutr. 2004;79(6):1118-1125. View publication
- Risérus U, Berglund L, Vessby B. Conjugated linoleic acid (CLA) reduced abdominal adipose tissue in obese middle-aged men with signs of the metabolic syndrome: a randomised controlled trial. Int J Obes Relat Metab Disord. 2001;25(8):1129-1135. View publication
- Office of Dietary Supplements, National Institutes of Health. Dietary supplements for weight loss: fact sheet for health professionals. View publication
- EFSA Panel on Dietetic Products, Nutrition and Allergies. Statement on the safety of the «conjugated linoleic acid (CLA)-rich oils» Clarinol® and Tonalin® TG 80 as novel food ingredients. EFSA Journal. 2012;10(5):2700. View publication
Information based on published studies. It does not replace the advice of a doctor or registered dietitian. The results describe what was measured in each study, not the properties of any specific product. A varied and balanced diet and a healthy lifestyle are important.
