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The Dark Side of CLA

Brian Turner

Posted on July 02 2018

By: Robert A. Schinetsky

 Conjugated Linoleic Acid (CLA) has garnered a reputation in the sports nutrition industry as one of the premier stimulant-free fat loss agents around for helping eliminate those unwanted pounds without giving you the jitters, edginess, or “uncomfortable” feeling typically experienced when using stimulant-based fat loss supplements.

 However, when put under the microscope of a more discerning eye, one not motivated by pure profit, you’ll quickly see that all is not so rosy with the “golden boy” of stim-free weight loss supplements. And with that, we come to the topic of today’s post -- the dark side of CLA.

 But, before we get into the potential dangers that accompany CLA supplementation, let’s backtrack and give a brief discussion of what CLA is and what its purported benefits are.

What is CLA?

 Conjugated linoleic acid (CLA) is a type of polyunsaturated fatty acid naturally occurring in the human body that’s similar to an omega-6 fatty acid. (It’s also technically a trans fat, which is typically thought of as a bad fat, but the “bad” trans fats are really the ones that are artificially created through partial hydrogenation.

 CLA is a naturally occurring fat in foods, and has been dubbed as one of the “good” fats present in beef and dairy products, due to it benefits related to weight loss and skin health, which we’ll get into more in a bit.

 The amounts of CLA in meat and dairy is rather low though, which makes obtaining enough CLA through whole foods alone rather difficult and expensive. In fact, the average intake of CLA for men and women in the United States is 212 mg / day and 151 mg / day, respectively.[1] FYI, this is far below the dosages needed to reap the fat loss benefits of CLA as documented in research trials.

 Speaking of research trials, let’s take a look at what research has to say concerning any fat loss benefits regarding this fat-burning fatty acid.

Does CLA Enhance Fat Loss?

 The primary reason CLA is so popular is due to some early research which noted that ingesting the fatty acid encouraged fat loss.

 Yes, you read that right -- eating fat actually helps lose fat...or at least this kind of fat did.

 Researchers first noted the fat-fighting effects of CLA back in 1997, when the fatty acid was shown to improve body composition in mice.[2] Various studies since that time have been conducted in humans and have noted that consuming between 1.4-3.0 grams per day of CLA leads to a reduction in body fat.[3,4]

 Given that you’d have to consume upwards of 100 oz of milk or 2 pounds of beef every day to get that much CLA in your system, supplementing with it makes sense, if you’re looking to possibly burn some extra fat.

 So, how does CLA encourage fat loss?

 Well, CLA potentially encourages fat loss through a number of different mechanisms[5]:

 First, CLA helps reduce food intake[6], and as you know weight loss is a function of energy out exceeding energy in, so anything that helps reduce the amount of food you eat technically promotes fat loss, indirectly that is. However, this reduction in food intake has only been shown in rats. No human studies on CLA to date have shown it successfully reduces food intake.

 Second, CLA increases energy expenditure[7], and as we just pointed out, weight loss is directly dependent on the balance of energy in versus energy out, so anything that reduces the former and/or increases the later (energy out) enhances weight loss. As such, by increasing your metabolic rate (i.e. the amount of calories you burn daily), CLA helps bolster fat loss.

 The third way in which CLA helps eliminate unwanted weight is by actually burning fat. CLA turns you into a fat burning machine by enhancing lipolysis -- the breakdown of stored body fat -- and fat oxidation (i.e. fat burning).[8,9] However, research conducted in 2005 noted that CLA’s body fat reducing effects were not due to lipolysis but due to its ability to inhibit preadipocyte differentiation into mature adipocytes.[10] Essentially, CLA supplementation prevent immature fat cells from growing into big, bad, ugly ones.

 Finally, some research indicates that CLA may actually accelerate fat loss by actually preventing your body from producing it.[11]

 This all sounds pretty great when viewed at a glance, but what’s neglected is that the vast majority of research touting the benefits of CLA has been conducted in rats. The majority of the research that has been conducted in humans has shown that it really has little to no significant impact on fat loss.

 In fact, a recent study from 2016 conducted by Ribeiro et al. showed that supplementing with 3.2 grams of CLA per day had NO significant effect on endurance, leg fat, trunk fat, or total body fat.[20]

 Upon completion of the study, researchers noted:

 “We conclude that CLA supplementation associated with aerobic exercise has no effect on body fat reduction and lipid profile improvements over placebo in young adult obese women.”[20]

 So, it would seem that CLA really isn’t the beacon of stim-free fat burning that it’s been touted to be. But, let’s say that for the moment CLA did have some kind of significant effect effect on fat loss.

 These potential fat burning effects of CLA don’t come without a severe drawback. As the saying goes, “there is no such thing as a free lunch” and what that means here is that while CLA may have some fat loss benefits, it does come at a cost, and a potentially serious one at that.

 This brings us to…

The Dark Side of CLA

 In two recent meta analyses, both from 2017, CLA was noted to increase inflammatory markers, including c-reactive protein (CRP) and tumor necrosis factor-α (TNF-α).[12,13] This led researchers to conclude that:

 “there are concerns about using CLA supplementation as an anti-obesity agent among the obese population for at least a short duration.”

 This is especially alarming when you consider the fact that systemic inflammation is an indicating factor in a whole host of diseases including:

- Heart Disease

- Rheumatoid arthritis

- Metabolic syndrome

- Diabetes

- Alzheimer’s

- Parkinson’s

- Lupus

- Irritable Bowel Syndrome

- Chronic Obstructive Pulmonary Disorder (COPD)

- And many others

As if that wasn’t bad enough, research has documented that large doses of supplemental CLA can lead to buildup of fat in the liver, which itself is an indicator of diabetes and metabolic syndrome.[14,15] CLA can also cause other less severe side effects including diarrhea, stomach pain, nausea and flatulence (exactly what you hope for in a supplement…).[18]

 And to top it off, human and animal research notes that even though CLA may help reduce body fat, it can still cause insulin resistance and decrease HDL ("good") cholesterol.[16,17]

Should You Use CLA?

 At the end of the day, the potential health complications that accompany even moderate doses of supplemental CLA make it a no-go in our book. The prospect of losing a few extra pounds don’t outweigh the host of problems that lurk with using CLA, and as such we do not include it in any of our supplements, including our day and nighttime fat burners Thermo Heat and Thermo Heat Nighttime.

 The fat loss benefits of CLA are questionable at best, and you can easily obtain the same fat loss benefits and avoid the unpleasant side effects from proper diet and hard exercise.

 In the end, don’t fall the for hype behind CLA. The consequences behind it are very real, and as such, it’s not worth putting your health and wellbeing at risk.



  1. Ritzenthaler KL, McGuire MK, Falen R, Shultz TD, Dasgupta N, McGuire MA. Estimation of conjugated linoleic acid intake by written dietary assessment methodologies underestimates actual intake evaluated by food duplicate methodology. J Nutr. 2001;131(5):1548-1554. doi:10.1093/jn/131.5.1548
  2. Park Y, Albright KJ, Liu W, Storkson JM, Cook ME, Pariza MW. Effect of conjugated linoleic acid on body composition in mice. Lipids. 1997;32(8):853-858.
  3. Mougios V, Matsakas A, Petridou A, Ring S, Sagredos A, Melissopoulou A,Tsigilis N, Nikolaidis M. Effect of supplementation with conjugated inoleic acid on human serum lipids and body fat. J NutrBiochem 2001;12:585-94
  4. Blankson H, Stakkestad JA, Fagertun H,Thom E, Wadstein J, Gudmundsen O. Conjugated linoleic acid reduces body fat mass in overweight and obese humans. J.Nutr. 130:2943-2948 (2000).
  5. Kennedy A, Martinez K, Schmidt S, Mandrup S, LaPoint K, McIntosh M. Antiobesity Mechanisms of Action of Conjugated Linoleic Acid. The Journal of nutritional biochemistry. 2010;21(3):171-179. doi:10.1016/j.jnutbio.2009.08.003.
  6. Miner JL, Cederberg CA, Nielsen MK, Chen X, Baile CA. Conjugated linoleic acid (CLA), body fat, and apoptosis. Obes Res. 2001;9:129–134.
  7. West DB, Blohm FY, Truett AA, DeLany JP. Conjugated linoleic acid persistently increases total energy expenditure in AKR/J mice without increasing uncoupling protein gene expression. J Nutr. 2000;130(10):2471-2477. doi:10.1093/jn/130.10.2471
  8. Evans M, Lin X, Odle J, McIntosh M. Trans-10, cis-12 conjugated linoleic acid increases fatty acid oxidation in 3T3-L1 preadipocytes. J Nutr. 2002;132(3):450-455. doi:10.1093/jn/132.3.450
  9. Lehnen TE, da Silva MR, Camacho A, Marcadenti A, Lehnen AM. A review on effects of conjugated linoleic fatty acid (CLA) upon body composition and energetic metabolism. Journal of the International Society of Sports Nutrition. 2015;12:36. doi:10.1186/s12970-015-0097-4.
  10. Simon E, Macarulla MT, Fernandez-Quintela A, Rodriguez VM, Portillo MP. Body fat-lowering effect of conjugated linoleic acid is not due to increased lipolysis. J Physiol Biochem. 2005;61(2):363-369.
  11. LaRosa PC, Miner J, Xia Y, Zhou Y, Kachman S, Fromm ME. Trans-10, cis-12 conjugated linoleic acid causes inflammation and delipidation of white adipose tissue in mice: a microarray and histological analysis. Physiol Genomics. 2006;27(3):282-294. doi:10.1152/physiolgenomics.00076.2006
  12. Mazidi M, Karimi E, Rezaie P, Ferns GA. Effects of conjugated linoleic acid supplementation on serum C-reactive protein: A systematic review and meta-analysis of randomized controlled trials. Cardiovasc Ther. 2017;35(6). doi:10.1111/1755-5922.12275
  13. Haghighatdoost F, Nobakht M Gh BF. Effect of conjugated linoleic acid on blood inflammatory markers: a systematic review and meta-analysis on randomized controlled trials. Eur J Clin Nutr. December 2017. doi:10.1038/s41430-017-0048-z
  14. Diwakar Vyas, Anil Kumar G. Kadegowda, and Richard A. Erdman, “Dietary Conjugated Linoleic Acid and Hepatic Steatosis: Species-Specific Effects on Liver and Adipose Lipid Metabolism and Gene Expression,” Journal of Nutrition and Metabolism, vol. 2012, Article ID 932928, 13 pages, 2012.
  15. Clement L, Poirier H, Niot I, et al. Dietary trans-10,cis-12 conjugated linoleic acid induces hyperinsulinemia and fatty liver in the mouse. J Lipid Res. 2002;43(9):1400-1409.
  16. Risérus U, Arner P, Brismar K, Vessby B. Treatment With Dietary trans10cis12 Conjugated Linoleic Acid Causes Isomer-Specific Insulin Resistance in Obese Men With the Metabolic Syndrome. Diabetes Care. 2002;25(9):1516 LP-1521.
  17. Risérus U, Basu S, Jovinge S, Fredrikson GN, Ärnlöv J, Vessby B. Supplementation With Conjugated Linoleic Acid Causes Isomer-Dependent Oxidative Stress and Elevated C-Reactive Protein. Circulation. 2002;106(15):1925 LP-1929.
  18. Gaullier J-M, Halse J, Hoye 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. doi:10.1093/ajcn/79.6.1118
  19. Henrietta Blankson, Jacob A. Stakkestad, Hans Fagertun, Erling Thom, Jan Wadstein, Ola Gudmundsen; Conjugated Linoleic Acid Reduces Body Fat Mass in Overweight and Obese Humans, The Journal of Nutrition, Volume 130, Issue 12, 1 December 2000, Pages 2943–2948,
  20. Ribeiro AS, Pina FLC, Dodero SR, et al. Effect of Conjugated Linoleic Acid Associated With Aerobic Exercise on Body Fat and Lipid Profile in Obese Women: A Randomized, Double-Blinded, and Placebo-Controlled Trial. Int J Sport Nutr Exerc Metab. 2016;26(2):135-144. doi:10.1123/ijsnem.2015-0236