Page updated Feb 19, 2019. First published Jul 17, 2013. No comments
Conjugated linoleic acid, in recent years, has emerged as an exciting anti-obesity agent. Apparently, not only does it cause fat loss but preserves lean mass as well. Increased metabolic rate, increased breakdown of fat, decreased formation of new fat, suppression of differentiation of preadipocytes into mature fat cell and apoptosis of fat cells are the some of the suggested mechanisms by which conjugated linoleic acid allegedly causes fat loss.
Although it is quite a popular weight-reducing agent, the scientific evidence is support of conjugated linoleic acid appears to be lacking.
Conjugated linoleic acid (CLA), in recent years, has emerged as an exciting anti-obesity agent. Not only does it cause fat loss but preserves lean mass as well. Thus, instead of just causing weight loss, CLA seems to improve body composition.
Let’s dig deeper into what CLA is, how – if at all – it causes fat loss and if there indeed is enough scientific evidence that it really does so.
Tell Me More About CLA – I’m Curious
Conjugated linoleic acid (as the term ‘conjugated’ suggests) is a mixture of 28 different isomers of octadecadienoic acid – (Rayalam, Della-Fera, & Baile, 2008; Kennedy et al., 2010).
Of the 28 different isomeric forms, cis-9, trans-11 (9, 11) and trans-10, cis-12 (10, 12) are the most abundant (Banni, 2002; Goncalves et al., 2010); these are also the most biologically active of all isomers (Wallace, McKain, Shingfield, & Devillard, 2007; Kennedy et al., 2010).
The 9, 11 isomer is called rumenic acid and constitutes the major chunk of CLA – 90% while the 10, 12 isomer makes up the rest. However, trans-10, cis-12 plays a bigger role in causing fat loss (Obsen et al., 2012; Park, Storkson, Albright, Liu, & Pariza, 1999; House et al., 2005; Brandebourg & Hu, 2005; Raff et al., 2009).
The only natural sources of conjugated linoleic acid are ruminant animals – red meat and dairy products (Goncalves et al., 2010; Obsen et al., 2012). Gastrointestinal microorganisms in the gut of these animals convert linoleic acid into the different isomers which together form the CLA (Kennedy et al., 2010).
Artificial food sources of CLA are dietary supplements and foods fortified with CLA (Obsen et al., 2012). Ruminants are not the source of commercially available CLA; it is synthesized from linoleic acid derived from safflower or sunflower oils (Wallace et al., 2007; Kennedy et al., 2010).
According to an estimate, the daily intake of CLA in non-vegetarians varies from 152mg to 212mg (Ritzenthaler et al., 2001). Needless to say, vegetarians, vegans and those with lactose intolerance will be hard pressed to eat enough CLA unless they use CLA fortified foods or supplements.
How Does CLA Aid Weight Loss?
CLA has been shown to reduce adiposity (fat content) in human and animals (Whigham, Watras, & Schoeller, 2007; Kennedy et al., 2010). How it does so, however, is not known (Obsen et al., 2012).
A few theories have been proposed by researchers to explain the fat-reducing abilities of CLA (Obsen et al., 2012; Kennedy et al., 2010; House et al., 2005; Brown et al., 2004).
Increased metabolic rate
Increased lipolysis (breakdown of fat)
Decreased adipogenesis (formation of new fat)
Suppression of differentiation of preadipocytes into mature fat cell
Apoptosis (cell death) of adipocytes (fat cells)
Additionally, CLA also improves body composition by preserving lean body mass.
What other health benefits can I expect from CLA?
In addition to its alleged weight-reducing abilities, it is believed that CLA affords numerous other health benefits (Silveira, Carraro, Monereo, & Tebar, 2007): improved immunity, treatment of oxidative stress, atherosclerosis, diabetes and cancer. Furthermore, it has also been shown to improve bone health as well.
In a nutshell, CLA supplementation – in addition to its anti-obesity actions – will:
Help fight oxidative stress
Help fight atherosclerosis
Help fight diabetes
Help fight cancer
What are the Daily Recommended Doses for CLA?
Similar to a number of other fat-loss agents, the daily recommended doses or indeed the maximum safety dose for CLA has not been defined. Various manufacturers have recommended dosages ranging from 1g to 3.4g daily (WebMD, 2013).
If in doubt, it is always better to consult your physician.
Does Research Say That CLA Causes Weight Loss As Well?
CLA and its effect on lipid metabolism have been extensively studied – in animals as well as in humans (Churruca, Fernandez-Quintela, & Portillo, 2009). Since the discovery of its anti-cancer action in 1987 and anti-atherosclerosis and anti-obesity properties subsequently, interest in CLA has slowly grown over the years (Whigham, Watras, & Schoeller, 2007; Mitchell & McLeod, 2008; Ha, Grimm, & Pariza, 1987).
Both animal and human studies have reported decrease in body fat when supplemented with CLA (Wang & Jones, 2004; Whigham et al., 2007). Park et al. showed conclusively that CLA improved body composition in animals (Park et al., 1997). Subsequently, numerous other animal studies have done so (Clement et al., 2002; Sisk, Hausman, Martin, & Azain, 2001).
In contrast to animal studies, however, CLA supplementation in humans has shown inconsistent results. While some studies report in favour of weight loss abilities of CLA (Gaullier et al., 2007; House, Cassady, Eisen, McIntosh, & Odle, 2005; Wang & Jones, 2004) others studies don’t do so (Nazare et al., 2007; Wang & Jones, 2004).
Research has it that CLA improves body composition – reduces body fat while preserving lean muscle mass – supplementing with CLA will cause fat loss while preserving lean muscles mass (Yang & Cook, 2003; Graves, Hitt, Pariza, Cook, & McCarthy, 2005). Due to the ability of CLA to preserve lean mass, its use in cancer-induced cachexia has been suggested by some. The results of use in cachexia, however, seem to be equivocal (Goncalves et al., 2010).
Thus, in theory, CLA seems to hold promise as an anti-obesity agent (Goncalves et al., 2010). However, the inconclusive results in human studies are a cause for concern and do not reflect well on the ability of CLA to cause weight loss.
Are There Any Health Risks of CLA Supplementation?
Going by current evidence, ingestion of CLA containing supplements or fortified foods is probably safe. Minor adverse-effects related to the gastrointestinal tract like nausea, mild vomiting or indigestion have been reported (Web MD, 2013). Rarely, CLA may cause fatigue.
Since not too much investigation has been conducted regarding the safety CLA consumption during pregnancy and lactation, it is better avoided during pregnancy and breastfeeding.
What Is Our Verdict On CLA?
CLA does seem to promise a lot as an anti-obesity and weight-loss agent. However, in the face of inconclusive scientific evidence we’d like to reserve our opinion on this one.
American Heart Association (2005). Economic cost of cardiovascular diseases, in Heart Disease and Stroke Statistics.
Banni, S. (2002). Conjugated linoleic acid metabolism. Curr.Opin.Lipidol., 13, 261-266.
Brandebourg, T. D. & Hu, C. Y. (2005). Isomer-specific regulation of differentiating pig preadipocytes by conjugated linoleic acids. J Anim Sci., 83, 2096-2105. Online Resource
Brown, J. M., Boysen, M. S., Chung, S., Fabiyi, O., Morrison, R. F., Mandrup, S. et al. (2004). Conjugated linoleic acid induces human adipocyte delipidation: autocrine/paracrine regulation of MEK/ERK signaling by adipocytokines. J Biol.Chem., 279, 26735-26747. Online Resource
Churruca, I., Fernandez-Quintela, A., & Portillo, M. P. (2009). Conjugated linoleic acid isomers: differences in metabolism and biological effects. Biofactors, 35, 105-111. Online Resource
Clement, L., Poirier, H., Niot, I., Bocher, V., Guerre-Millo, M., Krief, S. et al. (2002). Dietary trans-10,cis-12 conjugated linoleic acid induces hyperinsulinemia and fatty liver in the mouse. J Lipid Res., 43, 1400-1409. Online Resource
Gaullier, J. M., Halse, J., Hoivik, H. O., Hoye, K., Syvertsen, C., Nurminiemi, M. et al. (2007). Six months supplementation with conjugated linoleic acid induces regional-specific fat mass decreases in overweight and obese. Br.J Nutr., 97, 550-560. Online Resource
Goncalves, D. C., Lira, F. S., Carnevali, L. C., Jr., Rosa, J. C., Pimentel, G. D., & Seelaender, M. (2010). Conjugated Linoleic Acid: good or bad nutrient. Diabetol.Metab Syndr., 2, 62. Online Resource
Graves, E., Hitt, A., Pariza, M. W., Cook, M. E., & McCarthy, D. O. (2005). Conjugated linoleic acid preserves gastrocnemius muscle mass in mice bearing the colon-26 adenocarcinoma. Res.Nurs.Health, 28, 48-55. Online Resource
Ha, Y. L., Grimm, N. K., & Pariza, M. W. (1987). Anticarcinogens from fried ground beef: heat-altered derivatives of linoleic acid. Carcinogenesis, 8, 1881-1887. Online Resource
House, R. L., Cassady, J. P., Eisen, E. J., Eling, T. E., Collins, J. B., Grissom, S. F. et al. (2005). Functional genomic characterization of delipidation elicited by trans-10, cis-12-conjugated linoleic acid (t10c12-CLA) in a polygenic obese line of mice. Physiol Genomics, 21, 351-361.
House, R. L., Cassady, J. P., Eisen, E. J., McIntosh, M. K., & Odle, J. (2005). Conjugated linoleic acid evokes de-lipidation through the regulation of genes controlling lipid metabolism in adipose and liver tissue. Obes Rev, 6, 247-258. Online Resource
Kennedy, A., Martinez, K., Schmidt, S., Mandrup, S., LaPoint, K., & McIntosh, M. (2010). Antiobesity mechanisms of action of conjugated linoleic acid. J Nutr.Biochem., 21, 171-179. Online Resource
Leal, J., Luengo-Fernandez, R., Gray, A., Petersen, S., & Rayner, M. (2006). Economic burden of cardiovascular diseases in the enlarged European Union. Eur Heart J, 27, 1610-1619. Online Resource
Mitchell, P. L. & McLeod, R. S. (2008). Conjugated linoleic acid and atherosclerosis: studies in animal models. Biochem.Cell Biol., 86, 293-301. Online Resource
Nazare, J. A., de la Perriere, A. B., Bonnet, F., Desage, M., Peyrat, J., Maitrepierre, C. et al. (2007). Daily intake of conjugated linoleic acid-enriched yoghurts: effects on energy metabolism and adipose tissue gene expression in healthy subjects. Br.J Nutr., 97, 273-280. Online Resource
Obsen, T., Faergeman, N. J., Chung, S., Martinez, K., Gobern, S., Loreau, O. et al. (2012). Trans-10, cis-12 conjugated linoleic acid decreases de novo lipid synthesis in human adipocytes. J Nutr.Biochem., 23, 580-590. Online Resource
Park, Y., Albright, K. J., Liu, W., Storkson, J. M., Cook, M. E., & Pariza, M. W. (1997). Effect of conjugated linoleic acid on body composition in mice. Lipids, 32, 853-858. Online Resource
Park, Y., Storkson, J. M., Albright, K. J., Liu, W., & Pariza, M. W. (1999). Evidence that the trans-10,cis-12 isomer of conjugated linoleic acid induces body composition changes in mice. Lipids, 34, 235-241. Online Resource
Raff, M., Tholstrup, T., Toubro, S., Bruun, J. M., Lund, P., Straarup, E. M. et al. (2009). Conjugated linoleic acids reduce body fat in healthy postmenopausal women. J Nutr., 139, 1347-1352. Online Resource
Rayalam, S., Della-Fera, M. A., & Baile, C. A. (2008). Phytochemicals and regulation of the adipocyte life cycle. J Nutr.Biochem., 19, 717-726.
Ritzenthaler, K. L., McGuire, M. K., Falen, R., Shultz, T. D., Dasgupta, N., & McGuire, M. A. (2001). Estimation of conjugated linoleic acid intake by written dietary assessment methodologies underestimates actual intake evaluated by food duplicate methodology. J Nutr., 131, 1548-1554. Online Resource
Silveira, M. B., Carraro, R., Monereo, S., & Tebar, J. (2007). Conjugated linoleic acid (CLA) and obesity. Public Health Nutr., 10, 1181-1186. Online Resource
Sisk, M. B., Hausman, D. B., Martin, R. J., & Azain, M. J. (2001). Dietary conjugated linoleic acid reduces adiposity in lean but not obese Zucker rats. J Nutr., 131, 1668-1674. Online Resource
Wallace, R. J., McKain, N., Shingfield, K. J., & Devillard, E. (2007). Isomers of conjugated linoleic acids are synthesized via different mechanisms in ruminal digesta and bacteria. J Lipid Res., 48, 2247-2254. Online Resource
Wang, Y. W. & Jones, P. J. (2004). Conjugated linoleic acid and obesity control: efficacy and mechanisms. Int J Obes Relat Metab Disord, 28, 941-955.
Whigham, L. D., Watras, A. C., & Schoeller, D. A. (2007). Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. Am J Clin Nutr., 85, 1203-1211. Online Resource
Yang, M. & Cook, M. E. (2003). Dietary conjugated linoleic acid decreased cachexia, macrophage tumor necrosis factor-alpha production, and modifies splenocyte cytokines production. Exp.Biol.Med (Maywood.), 228, 51-58.
About the author: Rachel Butler
Rachel has been with us since we launched back in 2012.
Rachel has reviewed countless products over the years, and has written many articles offering sound advice. Her professional opinions are widely respected.
Rachel graduated a BSc in Clinical Science from the University of Leicester, U.K.
She lives in York with her husband and young daughter and their dog, a little terrier named Betsy.
Disclaimer: Our reviews and investigations are based on extensive research from the information publicly available to us and consumers at the time of first publishing the post. Information is based on our personal opinion and whilst we endeavour to ensure information is up-to-date, manufacturers do from time to time change their products and future research may disagree with our findings. If you feel any of the information is inaccurate, please contact us and we will review the information provided.