Key Takeaways
- CLA comes mainly from ruminant foods such as beef lamb and dairy.
- Natural food sources give small amounts that differ from supplement blends.
- Fat loss results from CLA supplements are usually modest and inconsistent.
- Some CLA forms may worsen insulin response liver markers or blood fats.
- Animal foods remain the most sensible way to get CLA in context.
CLA In Foods
CLA Basics
Conjugated linoleic acid is a group of fatty acids found mostly in the fat of ruminant animals such as cattle sheep and goats. The main natural form in food is called cis 9 trans 11 CLA. People usually eat it in beef lamb butter cheese and whole milk dairy.
CLA gets attention because it has been studied for body fat change inflammation blood fats and insulin response. Interest grew after early animal research looked promising. Human results have been much less impressive and often depend on the exact CLA form used in a study (1, 2, 3).
Natural CLA in food comes packaged with protein saturated fat minerals and other nutrients that support normal eating. Supplement CLA is usually a manufactured blend of isomers that does not match the balance found in beef or dairy. That difference matters when people try to apply food research to pills or softgels.
Best Sources
The richest common food sources are full fat dairy and meat from ruminant animals. Grass fed beef and dairy often contain more CLA than grain fed versions because the animal diet changes the fat profile. Lamb can also provide useful amounts.
Butter cheese yogurt cream whole milk beef and lamb are the usual places to get CLA from food. Lean cuts give less because CLA sits in the fat. People who remove animal fat from the plate often remove much of the CLA at the same time.
A simple way to get CLA from food is to eat fatty beef a few times each week and use full fat dairy if it suits you. A meal of ground beef with eggs or a plate of lamb with yogurt gives natural CLA without relying on a supplement. Natural intake will still be much lower than the large doses used in many trials.
Fat Loss Evidence
What Trials Show
CLA supplements can reduce fat mass in some studies, but the average effect is small. Meta analyses in adults usually find modest drops in body fat rather than major weight loss. Some trials show a little change in fat mass without much change on the scale, which tells you the effect is not dramatic in most real world settings (1, 2, 3).
One review found a reduction in fat mass with CLA supplementation, but the size was small enough that many people would barely notice it without careful tracking. Longer trials also reported some fat loss, yet the results still fell far short of what supplement marketing often suggests (4, 5, 6).
Exercise may improve body composition on its own, so CLA can look better in mixed programs than it does by itself. A recent review looking at CLA plus exercise still did not support the idea that CLA is a reliable shortcut for fat loss. Diet quality meal frequency sleep and total energy intake still shape the result far more than a single fatty acid supplement (7).
Why Results Stay Modest
The small effect likely comes from two problems. First, human metabolism is more complex than animal models. Second, CLA is not one single compound in practice. Different isomers can act differently in the body, and some may carry more risk than benefit.
People often hear about CLA as a fat burner. The data do not support that label. A fair reading says CLA supplements may nudge fat mass down a little in some adults, but the effect is inconsistent and often too small to justify routine use. Food sources make more sense because they come with nutrient dense animal foods that fit a low carb high fat way of eating.
Safety & Limits
Isomer Problems
The most important caution is that not all CLA acts the same. The trans 10 cis 12 form has raised concern in human studies because it may impair insulin sensitivity. In obese men with metabolic syndrome, one trial reported isomer specific insulin resistance after CLA exposure. Another study found less favorable effects on markers linked with inflammation and oxidative stress in obese men (8, 9).
Results like these explain why a food source is safer ground than a supplement blend. Beef and dairy contain CLA in a natural balance that the body has handled through normal diets for generations. Manufactured blends can push intake far above food levels and can shift the mix toward forms that do not look helpful.
Liver Blood Fats & Glucose
Safety questions do not stop with insulin response. Reviews have looked at liver enzymes blood lipids oxidative stress markers and blood pressure. Some pooled analyses found reason for caution rather than confidence, especially when higher doses and longer use were involved (10, 11, 12).
A person using CLA for months while expecting major fat loss could end up disappointed and still face unwanted shifts in lab markers. People with diabetes fatty liver metabolic syndrome or a history of high triglycerides have more reason to avoid casual supplement use. A pill that slightly trims fat mass but worsens glucose handling is not a clear win.
Food
Best Way To Use CLA
CLA works best as part of normal eating from animal foods rather than as a stand alone supplement. Full fat dairy, beef and lamb provide CLA in a form that comes with highly available protein fat soluble nutrients and minerals. Those foods also support stable meals without constant snacking.
One to three solid meals each day gives a better foundation for body composition than chasing isolated compounds. Eggs with butter at breakfast or a beef meal with cheese later in the day will do more for appetite control than a capsule added to a low fat processed diet. People seeking fat loss usually do better when they lower sugar starch seed oils and ultra processed foods while keeping enough animal fat to stay satisfied.
Who Should Skip Supplements
CLA supplements make the least sense for people who already eat ruminant foods. They also make little sense for anyone expecting fast weight loss. The research does not support that hope.
A person who still wants to try CLA should know the evidence is mixed, the average effect is small and safety signals exist. Natural sources remain the safer choice. Beef, lamb and full fat dairy are the most direct way to get CLA while keeping the wider diet simple and nutrient dense.
For any health concerns or questions about a medical condition, get guidance from a physician or another appropriately trained clinician. Before changing your diet, supplements or health routine, talk with a licensed healthcare professional.
FAQs
What is CLA?
CLA is a group of fatty acids found mostly in the fat of ruminant animals such as cows and sheep. People get it from beef lamb butter cheese and whole milk dairy. Supplements usually contain a manufactured blend of CLA forms.
Does CLA help with fat loss?
CLA supplements may reduce fat mass a little in some adults, but the average effect is modest. Many people would not notice a major visible change from CLA alone.
What foods contain the most CLA?
The main sources are fatty beef lamb butter cheese cream and other full fat dairy foods. Grass fed beef and dairy often contain more CLA than grain fed versions.
Is CLA safe to take every day?
Daily CLA supplement use is not clearly harmless. Some studies raised concerns about insulin response liver markers blood fats and inflammatory markers, especially with certain isomers or longer use.
Is food better than a CLA supplement?
Food is the better starting point for most people. Beef lamb and full fat dairy give CLA in a natural mix along with protein fat and minerals that fit a simple animal based diet.
Research
Whigham, L.D., Watras, A.C. and Schoeller, D.A. (2007) ‘Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans’, American Journal of Clinical Nutrition, 85(5), pp. 1203–1211. Available at: https://doi.org/10.1093/ajcn/85.5.1203.
Asbaghi, O., Tamtaji, O.R., Sadeghian, M. and Miraghajani, M. (2024) ‘The effects of conjugated linoleic acid supplementation on anthropometrics and body composition indices in adults: A systematic review and dose–response meta-analysis’, British Journal of Nutrition, 131(3), pp. 406–428. Available at: https://doi.org/10.1017/S0007114523001861.
Onakpoya, I.J., Posadzki, P.P., Watson, L.K. and Ernst, E. (2012) ‘The efficacy of long-term conjugated linoleic acid supplementation on body composition in overweight and obese individuals: a systematic review and meta-analysis of randomized clinical trials’, European Journal of Nutrition, 51(2), pp. 127–134. Available at: https://doi.org/10.1007/s00394-011-0253-9.
Blankson, H., Stakkestad, J.A., Fagertun, H., Thom, E., Wadstein, J. and Gudmundsen, O. (2000) ‘Conjugated linoleic acid reduces body fat mass in overweight and obese humans’, Journal of Nutrition, 130(12), pp. 2943–2948. Available at: https://doi.org/10.1093/jn/130.12.2943.
Gaullier, J.-M., Halse, J., Høivik, H.O., Høye, K., Syvertsen, C., Nurminiemi, M., Hassfeld, C., Einerhand, A. and Gudmundsen, O. (2004) ‘Conjugated linoleic acid supplementation for 1 y reduces body fat mass in healthy overweight humans’, American Journal of Clinical Nutrition, 79(6), pp. 1118–1125. Available at: https://doi.org/10.1093/ajcn/79.6.1118.
Gaullier, J.-M., Høye, K., Kristiansen, K., Fagertun, H., Vik, H., Gudmundsen, O. and Hervik, K. (2005) ‘Supplementation with conjugated linoleic acid for 24 months is well tolerated by and reduces body fat mass in healthy, overweight humans’, Journal of Nutrition, 135(4), pp. 778–784. Available at: https://doi.org/10.1093/jn/135.4.778.
Liang, C.-W., Chang, Y.-L., Chen, Y.-C. and Chao, A.M. (2023) ‘Effects of conjugated linoleic acid and exercise on body composition and obesity: a systematic review and meta-analysis’, Nutrition Reviews, 81(4), pp. 397–415. Available at: https://doi.org/10.1093/nutrit/nuac060.
Risérus, U., Arner, P., Brismar, K. and Vessby, B. (2002) ‘Treatment with dietary trans10cis12 conjugated linoleic acid causes isomer-specific insulin resistance in obese men with the metabolic syndrome’, Diabetes Care, 25(9), pp. 1516–1521. Available at: https://doi.org/10.2337/diacare.25.9.1516.
Risérus, U., Basu, S., Jovinge, S., Fredrikson, G.N., Arnlöv, J. and Vessby, B. (2004) ‘Effects of cis-9,trans-11 conjugated linoleic acid supplementation on insulin sensitivity, lipid peroxidation, and proinflammatory markers in obese men’, American Journal of Clinical Nutrition, 80(2), pp. 279–283. Available at: https://doi.org/10.1093/ajcn/80.2.279.
Haghighat, N., Mirzadeh, M., Ghodoosi, N., Ghavami, A., Clark, C.C.T. and Rouhani, M.H. (2022) ‘The effects of conjugated linoleic acid supplementation on liver function enzymes and malondialdehyde in adults: A GRADE-assessed systematic review and dose-response meta-analysis’, Pharmacological Research, 186, 106518. Available at: https://doi.org/10.1016/j.phrs.2022.106518.
Asbaghi, O., Tamtaji, O.R., Sadeghian, M. and Miraghajani, M. (2022) ‘The effects of conjugated linoleic acid supplementation on lipid profile in adults: A systematic review and dose-response meta-analysis’, Frontiers in Nutrition, 9, 953012. Available at: https://doi.org/10.3389/fnut.2022.953012.
Mazidi, M., Karimi, E., Rezaie, P., Ferns, G.A. and Vatanparast, H. (2017) ‘Effects of conjugated linoleic acid supplementation on serum C-reactive protein: A systematic review and meta-analysis of randomized controlled trials’, Cardiovascular Therapeutics, 35(6). Available at: https://doi.org/10.1111/1755-5922.12275.
Asbaghi, O., Tamtaji, O.R., Sadeghian, M. and Miraghajani, M. (2022) ‘The effects of conjugated linoleic acid supplementation on blood pressure and endothelial function in adults: A systematic review and dose-response meta-analysis’, European Journal of Pharmacology, 931, 175162. Available at: https://doi.org/10.1016/j.ejphar.2022.175162.
Derakhshande-Rishehri, S.-M., Mansournia, M.A., Kelishadi, R. and Heidari-Beni, M. (2015) ‘Association of foods enriched in conjugated linoleic acid (CLA) and CLA supplements with lipid profile in human studies: a systematic review and meta-analysis’, Public Health Nutrition, 18(11), pp. 2041–2054. Available at: https://doi.org/10.1017/S1368980014002262.
Suksatan, W., Phisalprapa, P., Chonwerawong, M., Trelfa, A., Prombutara, P., Boonchooduang, N., Chantarangkul, C. and Prajongjeep, A. (2022) ‘The effect of conjugated linoleic acid supplementation on oxidative stress markers: A systematic review and meta-analysis of randomized controlled trials’, Clinical Nutrition ESPEN, 49, pp. 121–128. Available at: https://doi.org/10.1016/j.clnesp.2022.04.004.
Morvaridzadeh, M., Mottaghi, A., Agah, S., Askari, G., Heshmati, J. and Hekmatdoost, A. (2022) ‘The effect of Conjugated Linoleic Acid intake on oxidative stress parameters and antioxidant enzymes: A systematic review and meta-analysis of randomized clinical trials’, Prostaglandins & Other Lipid Mediators, 163, 106666. Available at: https://doi.org/10.1016/j.prostaglandins.2022.106666.
Mirzaii, S., Ghiasvand, R., Askari, G., Feizi, A., Hariri, M. and Darvishi, L. (2016) ‘Association of conjugated linoleic acid consumption and liver enzymes in human studies: A systematic review and meta-analysis of randomized controlled clinical trials’, Nutrition, 32(2), pp. 166–173. Available at: https://doi.org/10.1016/j.nut.2015.08.013.
Ghodoosi, N., Mirzadeh, M., Rahimi Sakak, F., Ghavami, A., Clark, C.C.T. and Rouhani, M.H. (2023) ‘The effects of conjugated linoleic acid supplementation on glycemic control, adipokines, cytokines, malondialdehyde and liver function enzymes in patients at risk of cardiovascular disease: a GRADE-assessed systematic review and dose-response meta-analysis’, Nutrition Journal, 22(1), 47. Available at: https://doi.org/10.1186/s12937-023-00876-3.
Moloney, F., Toomey, S., Noone, E., Nugent, A., Allan, B., Loscher, C.E., Roche, H.M. and Gibney, M.J. (2004) ‘Conjugated linoleic acid supplementation, insulin sensitivity, and lipoprotein metabolism in patients with type 2 diabetes mellitus’, American Journal of Clinical Nutrition, 80(4), pp. 887–895. Available at: https://doi.org/10.1093/ajcn/80.4.887.
Wanders, A.J., Brouwer, I.A., Siebelink, E., Katan, M.B. and Mensink, R.P. (2010) ‘Effect of a high intake of conjugated linoleic acid on lipoprotein levels in healthy human subjects’, PLoS ONE, 5(2), e9000. Available at: https://doi.org/10.1371/journal.pone.0009000.
Smit, L.A., Baylin, A. and Campos, H. (2010) ‘Conjugated linoleic acid in adipose tissue and risk of myocardial infarction’, American Journal of Clinical Nutrition, 92(1), pp. 34–40. Available at: https://doi.org/10.3945/ajcn.2010.29524.
Wannamethee, S.G., Lennon, L., Papacosta, O., Whincup, P., Bruckdorfer, K.R. and Sattar, N. (2018) ‘Serum Conjugated Linoleic Acid and Risk of Incident Heart Failure in Older Men: The British Regional Heart Study’, Journal of the American Heart Association, 7(1), e006653. Available at: https://doi.org/10.1161/JAHA.117.006653.
Larsson, S.C., Bergkvist, L. and Wolk, A. (2009) ‘Conjugated linoleic acid intake and breast cancer risk in a prospective cohort of Swedish women’, American Journal of Clinical Nutrition, 90(3), pp. 556–560. Available at: https://doi.org/10.3945/ajcn.2009.27480.
