Conjugated linoleic acid (CLA) is a fatty acid that is naturally occurring and can be found primarily in meat and dairy products. Supplementing CLA may provide benefits to energy metabolism and body composition through reducing fat mass and increasing lean body mass. It is reported that supplementing CLA decreases lipogenesis and increases lipolysis, fat oxidation, and energy expenditure. CLA may also improve body composition and energy metabolism through improved lipid profile and anti-inflammatory effects that can reduce oxidative stress and mitigate insulin signaling. (Macaluso 2013, Lehnen 2015)
Few studies in humans have examined the effect of CLA on body composition alone or combined with exercise (Lehnen 2015). However, there is some evidence that CLA supplementation may reduce body fat mass and improve body composition. A meta-analysis examining the effects on reducing fat mass demonstrated CLA does cause a modest, yet significant reduction in fat loss of 0.09kg/week compared to placebo (Whigham 2007). Evidence also shows CLA supplementation in combination with standardized and supervised resistance training increases lean body mass and decreases fat mass (Macaluso 2013). Similarly, a combination of CLA with regular training consisting of aerobic and strength exercises has been shown to be effective in improving muscle contractile performance and body composition (Miller 2010).
Daily doses of CLA studied for improvements in body composition were around 3-6g/day, although no additional benefits have been reported for higher doses than this. Adverse effects in humans include increased triglyceride levels, increased LDL-cholesterol, and reduced HDL-cholesterol. Adverse gastrointestinal effects have also been reported, but CLA appears to be safe for use. (Lehnen 2015, Egras 2011)
Overall, clinical evidence appears to be insufficient and inconclusive regarding body fat reduction with CLA supplementation (Lehnen 2015). The effect of CLA on body composition remains controversial, as significant effects on body fat are not consistently reported (Whigham 2007).
Egras AM, Hamilton WR, Lenz TL, Monaghan MS (2011). An Evidence-Based Review of Fat Modifying Supplemental Weight Loss Products. Journal of Obesity, 2011, 1-7.
Lehnen TE, da Silva MR, Camacho A, Marcadenti A, Lehnen AM (2015). A review on effects of conjugated linoleic fatty acid (CLA) upon body composition and energetic metabolism. Journal of the International Society of Sports Nutrition, 12(1), 36.
Macaluso F, Barone R, Catanese P, Carini F, Rizzuto L, Farina F, Di Felice V (2013). Do fat supplements increase physical performance?. Nutrients, 5(2), 509-24.
Miller PC, Chao GK, Burns JD, Bixby WR, Hall EE (2010). Effects of CLA Supplementation on Muscle Performance and Lean Mass Following Seven Weeks of Exercise. Medicine & Science in Sports & Exercise, 42(5), 447-448.
Whigham LD, Watras AC, Schoeller DA (2007). Efficacy of conjugated linoleic acid for reducing fat mass: a meta-analysis in humans. The American Journal of Clinical Nutrition. 85(5):1203–1211.