Conjugated Linoleic Acid (CLA) is a fatty acid (an isomer of linoleic acid) found naturally in foods such as dairy products and red meat. A number of studies have shown increases in lean body mass and decreases in body fat from supplementation of CLA. Problem is, nearly all of these studies were done on rats and mice! Whether or not CLA improves body composition in humans still has yet to be proven because human research studies are few in number and the results are conflicting.

What I find ironic is that in the mid to late 90's when CLA was first marketed like crazy in the magazines as a "miracle" fat burner and muscle builder, all the hype was based on the animal studies alone! Although the initial hype has long since faded (because people tried it and nothing happened), CLA keeps popping up in the muscle mags and on the Internet to this day each time a new human study is completed.

Back in the days when he owned EAS supplement company, Bill Phillips was one of the first to promote CLA in Muscle Media magazine and in his Sports Supplement review book. However, even Mr. Phillips was quick to point out that the data wasn't conclusive. Phillips said, "CLA isn't yet 'tried and true,' so it didn't make my top ten supplements list. The animal data is compelling. It has been postulated from these studies that CLA may be a growth factor for at least some species. Whether or not this translates to humans at this point is somewhat up in the air."

At least Phillips was up front about the research, but that didn't stop him (or other "supplement gurus") from selling the stuff. Basically, Phillips was saying that the animal research looks promising and it might do something in humans, so if you want to try it, I'll be happy to sell it to you.

There have indeed been some human studies in the past several years, but the research is very limited and far from conclusive. In one study by Lowery et al ("CLA enhances muscle size an strength gains in novice body builders," Medicine & Science in Sports and Exercise, 1998, 30: S182), gains in arm size were greater in the CLA supplemented group than the placebo group.

There were no differences however, in body fat. In a "Fat Roundtable" discussion from Testosterone Magazine, the author of this study himself, Lonnie Lowery, pointed out that "Despite often rigorous dietary and activity controls, I've yet to see CLA affect fat mass in weight trained men at any dose. It (CLA) just doesn't seem to do anything for leaning-out active adult men."

Folks, let me warn you about something. When you see those brief columns in the muscle magazines quoting a new research study "proving" that a supplement works, do not accept the claims at face value until you have dug a little deeper! For example, further analysis of the 1998 MSSE study by other researchers suggested "Questionable methodology in measurement of arm girth." Antonio and Stout, writing in the book Sports Supplements, note that, "The (author's) interpretation of the data is not appropriate... In a sense, the authors are looking for something that is not there."

Furthermore, while there are now selected human studies that suggest fat loss or muscle building benefits of CLA, there are just as many studies that show the exact opposite. Supplement companies are quick to selectively quote studies that show positive findings, but naturally, they make no mention of the rest of the body of research on the subject. In a 2002 study by Krieder, et al in the Journal of Strength and Conditioning Research, no difference in lean body mass, fat mass or strength was found after 4 weeks of supplementation and resistance training in a group given 6 grams of CLA versus a control group given a placebo.

What do other experts say? In "An evaluation of popular Fitness-Enhancing Supplements," the authors Neal Spruce and Allen Titchenal, PhD., agree: "Much work needs to be done to determine if CLA can help to reduce body fat in humans."

Phil Kaplan, a fitness consumer advocate and author of The Best You've Ever Been says, "CLA has been making a few headlines as a fat burner, and those headlines use the all-too-common words, 'research has proven.' The problem with these words is compounded by the fact that supplement sellers will only share research that appears to lend some credence to their offerings. Personally I'm not sold on CLA. It's expensive and the preponderance of available evidence suggests that it isn't a bodybuilding or fat loss aid."

In Diet Supplements Revealed, Independent researcher and industry columnist Will Brink says, "Although some of the findings with CLA in people have been exciting and interesting, there continues to be too many conflicting studies. For increasing muscle mass or improving performance, CLA gets a thumbs down until more human research is done."

Although CLA may have possible health benefits, it is still completely unproven as a fat burner or muscle builder in healthy humans, not to mention it's expensive and probably not cost effective even if it did have some small benefit. If you look closely at the studies, you'll see that the dosages given were enormous:

According to John Ivy, PhD., and Robert Portman, PhD., authors of Nutrient Timing, "Some research has shown that supplemental CLA can reduce body fat content. however, this effect has been shown only in laboratory mice that received massive quantities of CLA, which humans could never practically match pound for pound. While CLA is an important nutrient, it is probably not a worthwhile supplement for reducing body fat or increasing muscle strength."

Bottom line: Essential fatty acids (EFA's) are very important in human nutrition. I would recommend however, that you skip the CLA and instead focus on fixing your diet before even considering any supplements. Then, after you're sure you're getting plenty of EFA's from your food, if you want to take an EFA supplement, consider flaxseed oil or an essential oil blend such as Udo's Choice. Another option is fish oil, although, again, fix your diet first: If you eat fatty fish such as Salmon a couple times per week, you've got yourself covered.

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This article was provided courtesy of Tom Venuto and www.burnthefat.com. Tom is a lifetime natural bodybuilder, personal trainer, gym owner, freelance writer and author of "Burn the Fat, Feed The Muscle" (BFFM): Fat Burning Secrets of the World's Best Bodybuilders and Fitness Models.

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