Conjugated Linoleic Acid for Weight Control

Also known as: CLA

What does it do?

Conjugated linoleic acid (CLA) is a slightly altered form of the essential fatty acid linoleic acid.

Where is it found?

CLA is found mainly in dairy products and also in beef and poultry, eggs, and corn oil. Bacteria that live in the intestine of humans can produce CLA from linoleic acid, but supplementation of a rich source of linoleic acid did not produce increases in blood levels of CLA in one human study.1 CLA is available as a supplement.

Why do dieters use it?*

Some dieters say that CLA

What do the advocates say?*

Research suggests that conjugated linoleic acid (CLA) may help to reduce body fat and increase muscle. The research supporting CLA’s ability to help reduce body fat is good, but more is needed. There are at least seven human studies (two are double-blind and the others are controlled) showing significant reduction of abdominal obesity and body fat mass in overweight and moderately obese people. However, since most of the studies involved a small number of participants and were short in duration, larger double-blind studies are needed to further document the benefits and mechanisms of action.

Although CLA promotes weight loss, which is good for heart health, it is important to moniter cholesterol levels as it may reduce HDL (“good”) cholesterol.

How much is usually taken by dieters?

A double-blind trial found that exercising individuals taking 1,800 mg per day of CLA lost more body fat after 12 weeks than a similar group taking a placebo.2 However, two other studies found that amounts of CLA from 0.7 to 3.0 grams per day did not affect body composition.3 4 Most double-blind trials have found that larger amounts of CLA, 3.4 to 4.2 grams per day, does reduce body fat;5 6 7 however, one double-blind study of experienced strength-training athletes reported no effect of 6 grams per day of CLA on body fat, muscle mass, or strength improvement.8

Are there any side effects or interactions?

The side effects of CLA are unknown, due to the limited research in humans. However, one unpublished human trial reported isolated cases of gastrointestinal upset.9

At the time of writing, there were no well-known drug interactions with conjugated linoleic acid.

Resources

See a list of books, periodicals, and other resources for this and related topics.

*Dieters and weight-management advocates may claim benefits for CLA based on their personal or professional experience. These are individual opinions and testimonials that may or may not be supported by controlled clinical studies or published scientific articles on CLA. For more complete and detailed information, including references and safety information, see CLA as a nutritional supplement.

References

1. Herbel BK, McGuire MK, McGuire MA, et al. Safflower oil consumption does not increase plasma conjugated linoleic acid concentrations in humans. Am J Clin Nutr 1998;67:332–7.

2. Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat in healthy exercising humans. J Int Med Res 2001;29:392–6.

3. Mougios V, Matsakas A, Petridou A, et al. Effect of supplementation with conjugated linoleic acid on human serum lipids and body fat. J Nutr Biochem 2001;12:585–94.

4. Zambell KL, Keim NL, Van Loan MD, et al. Conjugated linoleic acid supplementation in humans: effects on body composition and energy expenditure. Lipids 2000;35:777–82.

5. Riserus 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;25:1129–35.

6. Smedman A, Vessby B. Conjugated linoleic acid supplementation in humans—metabolic effects. Lipids 2001;36:773–81.

7. Blankson H, Stakkestad JA, Fagertun H, et al. Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J Nutr 2000;130:2943–8.

8. Kreider RB, Ferreira MP, Greenwood M, et al. Effects of conjugated linoleic acid supplementation during resistance training on body composition, bone density, strength, and selected hematological markers. J Strength Cond Res 2002;16:325–34.

9. Thom E. A pilot study with the aim of studying the efficacy and tolerability of Tonalin CLA on the body composition in humans. Lillestrom, Norway: Medstat Research Ltd., July 1997 [unpublished].