Conjugated linoleic acid, or CLA, can be a divisive supplement in health and fitness circles. You'll find no shortage of people who swear it helped them get shredded while keeping muscle mass, or helped them turn the corner and leave obesity behind. It's also a near-mandatory ingredient in non-stimulant fat burners, and many other weight management blends.

However, the science hasn't always been supportive of CLA supplements' appeal. Should this fatty acid be a staple in your fat-loss stack? Here's where the research currently stands.

What is CLA?

CLA is a term used to refer to the family of different isomers of linoleic acid known collectively as conjugated linoleic acid. Found naturally in dairy, linoleic acids are a type of polyunsaturated fatty acids, and they exert a variety of physiological functions in the body. Due to some positive results in body composition studies, CLA is often considered a fat-loss supplement. It's found in fat-burner supplements and is a regular feature in many bodybuilding cutting stacks.[1]

What Does CLA Do?

Most of this fatty acid's fat-burning claims rely on its effect on the PPAR system, a signaling receptor family related to a number of metabolic functions in the body including fat burning and natural steroid signaling. This is an example of how, yes, sometimes you have to ingest fat to be able to lose fat (although the amount of fat conjugated linoleic acid adds to your diet is negligible).

What Are the Benefits of CLA?

CLA has been suggested to improve lean body mass, reduce body fat, aid in weight loss, and raise metabolism when used as a dietary supplement.[2]

Animal studies show initial promise, although most human trials show little effect on body composition or muscle mass in healthy, active adults. Many of the studies showing modest benefits of CLA supplements on body composition have been conducted in obese or sedentary individuals.[3-7] Some research indicates that a dose of approximately 3.4 grams per day for 6-12 months might elicit mild improvements in body composition in overweight, untrained populations.[8,9] However, it's worth repeating that this is a relatively long-term effect; if you're going to take it, be prepared to do so for at least six months.

Based on the research, CLA supplementation alone is unlikely to exert noticeable body composition benefits in highly trained or already lean individuals. However, as mentioned previously, many die-hard fans swear by this supplement while cutting for its potential anti-catabolic effects.

So, does it stack up for fat loss? Canadian researchers gave CLA to subjects for seven weeks, while they were also weight training three times a week. Participants who used this supplement had greater increases in lean tissue mass (1.4 kilograms) versus the control group (0.2 kilograms). The authors concluded that the small increase in lean body mass may be attributed to a decreased catabolic effect that came from the CLA supplementation.[4]

What Other Health Benefits Are There?

Generally, while there is some promising data from animal studies on the health effects of CLA supplementation, results in human trials have been much shakier. Populations with pre-existing conditions such as high blood pressure or obesity have been the only ones to appear to benefit from supplementation. More research is definitely necessary.

Here's some of what has been studied:

Hearth Health: Supplementing with 4.5 grams of conjugated linoleic acid for eight weeks was associated with healthy blood pressure levels in hypertensive participants.[10] A more recent meta-analysis of studies done looking at the effects of CLA supplementation found it was most likely to have greater beneficial effects in people with hypertension, rather than those with normal blood pressure.[13]

Immune System and Inflammation: This supplement has also been shown to exhibit beneficial effects on immune and inflammatory response in animal models.[11] However, conclusive data on its positive effects in human trials is still lacking.[1,12]

What Are the Side Effects of CLA?

There is potential for gastrointestinal distress with high doses of CLA supplementation, but it's considered safe and shouldn't cause side effects in reasonable doses.[13]

There are currently no known drug interactions with CLA supplementation, and it is considered safe for human consumption.

Are There Any Dietary Forms of CLA?

CLA is naturally found in meat and dairy products, although the overall intake from diet is inconsequential due to it being available only in trace amounts and much lower than the typical doses seen in supplementation research. Eating more dairy products and meat won't raise your levels of this fatty acid that much—you need to take it as a dietary supplement to make a difference.

What Are the Available Forms of CLA?

There are a variety of forms of CLA available, including powders and pills. But it's most commonly consumed in softgel or capsule form.

How Much CLA Should You Take?

Doses used in studies range from 1.4 grams per day to 6.8 grams per day. While there is considerable variation in dosing protocols between studies, the most commonly recommended dose is 3.4 grams per day.[3,10]

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References

1. Viladomiu, M., Hontecillas, R., & Bassaganya-Riera, J. (2016). Modulation of inflammation and immunity by dietary conjugated linoleic acid. European Journal of Pharmacology, 785, 87-95.
2. Haff, G. G. (2008). Essentials of Sports Nutrition Study Guide. Essentials of Sports Nutrition Study Guide: by Gregory G. Haff, ISBN 978-1-58829-611-5. Humana Press, 2008.
3. Blankson, H., Stakkestad, J. A., Fagertun, H., Thom, E., Wadstein, J., & Gudmundsen, O. (2000). Conjugated linoleic acid reduces body fat mass in overweight and obese humans. The Journal of Nutrition, 130(12), 2943-2948.
4. Pinkoski, C., Chilibeck, P. D., Candow, D. G., Esliger, D., Ewaschuk, J. B., Facci, M., ... & Zello, G. A. (2006). The effects of conjugated linoleic acid supplementation during resistance training. Medicine and Science in Sports and Exercise, 38(2), 339-348.
5. Chen, S. C., Lin, Y. H., Huang, H. P., Hsu, W. L., Houng, J. Y., & Huang, C. K. (2012). Effect of conjugated linoleic acid supplementation on weight loss and body fat composition in a Chinese population. Nutrition, 28(5), 559-565.
6. Joseph, S. V., Jacques, H., Plourde, M., Mitchell, P. L., McLeod, R. S., & Jones, P. J. (2011). Conjugated linoleic acid supplementation for 8 weeks does not affect body composition, lipid profile, or safety biomarkers in overweight, hyperlipidemic men. The Journal of Nutrition, 141(7), 1286-1291.
7. Norris, L. E., Collene, A. L., Asp, M. L., Hsu, J. C., Liu, L. F., Richardson, J. R., ... & Belury, M. A. (2009). Comparison of dietary conjugated linoleic acid with safflower oil on body composition in obese postmenopausal women with type 2 diabetes mellitus. The American Journal of Clinical Nutrition, 90(3), 468-476.
8. Gaullier, J. M., Halse, J., Hoivik, H. O., Hoye, K., Syvertsen, C., Nurminiemi, M., ... & Gudmundsen, O. (2007). Six months supplementation with conjugated linoleic acid induces regional-specific fat mass decreases in overweight and obese. British Journal of Nutrition, 97(3), 550-560.
9. Gaullier, J. M., Halse, J., Hoye, K., Kristiansen, K., Fagertun, H., Vik, H., & Gudmundsen, O. (2004). Conjugated linoleic acid supplementation for 1 y reduces body fat mass in healthy overweight humans. The American Journal of Clinical Nutrition, 79(6), 1118-1125.
10. Zhao, W. S., Zhai, J. J., Wang, Y. H., Xie, P. S., Yin, X. J., Li, L. X., & Cheng, K. L. (2009). Conjugated linoleic acid supplementation enhances antihypertensive effect of ramipril in Chinese patients with obesity-related hypertension. American Journal of Hypertension, 22(6), 680-686.
11. Yang, M., & Cook, M. E. (2003). Dietary Conjugated Linoleic Acid Decreased Cachexia, Macrophage Tumor Necrosis Factor-a Production, and Modifies Splenocyte Cytokines Production. Experimental Biology and Medicine, 228(1), 51-58.
12. Dilzer, A., & Park, Y. (2012). Implication of conjugated linoleic acid (CLA) in human health. Critical Reviews in Food Science and Nutrition, 52(6), 488-513.
13. Yang, J., Wang, H. P., Zhou, L. M., Zhou, L., Chen, T., & Qin, L. Q. (2015). Effect of conjugated linoleic acid on blood pressure: a meta-analysis of randomized, double-blind placebo-controlled trials. Lipids in Health and Disease, 14(1), 11.