Clinical trials have indicated conflicting results on the effects of conjugated linoleic acid (CLA) on obesity. The present study aimed to systematically review controlled clinical trials examining the effects of CLA on anthropometric indices and body composition in overweight and obese subjects. Pubmed, Scopus, Web of science, and Cochrane databases were searched between 2000 and December 2017 with no language restriction. Placebo-controlled clinical trials that reported anthropometric indices and body composition in overweight and obese subjects were included. Random-effect model was used to pool the effect estimates. Of 4032 publications, 13 trials were included for the meta-analysis. Pooled effect sizes indicated that CLA significantly reduced body weight (WMD: -0.52 kg, 95% CI: -0.83, -0.21; I2: 48.0%, p = 0.01), BMI (WMD: -0.23 kg/m2, 95% CI: -0.39, - 0.06; I2: 64.7%, p = 0.0001), FM (WMD: -0.61 kg, 95% CI: -0.98, -0.24; I2: 53.8%, p = 0.01) and increased LBM (WMD: 0.19 kg, 95% CI: 0.04, 0.34; I2: 81.4%, p = 0.0001) compared to the placebo group. However, the effects of CLA on WC (WMD: 0.05 cm, 95% CI: -0.01, 0.1; I2: 0%, p = 0.93) was not significant. Additionally, its impact on body weight in subjects older than 44 year (WMD: -1.05 kg, 95% CI: -1.75, -0.35; I2: 57.0%, p = 0.01), with longer duration (more than 12 weeks) (WMD: -1.29 kg, 95% CI: -2.29, -0.29; I2: 70.3%, p = 0.003) and dosage more than 3.4 g/day (WMD: -0.77 kg, 95% CI: -1.28, -0.25; I2: 62.7%, p = 0.004) were greater than comparative groups. Supplementation with CLA can slightly reduce body weight and FM and increase LBM in overweight and obese subjects. However, its efficacy was not clinically considerable. Further studies with high methodological quality are needed to shed light on the effects of CLA on anthropometric indices in overweight and obese subjects.
Keywords: CLA; WC; body composition; obesity.