Br J Nutr. 2023 Sep 6:1-47. doi: 10.1017/S0007114523001861. Online ahead of print.
Prior meta-analytic investigations over a decade ago rather inconclusively indicated that conjugated linoleic acid (CLA) supplementation could improve anthropometric and body composition indices in the general adult population. More recent investigations have emerged, and an up-to-date systematic review and meta-analysis on this topic must be improved. Therefore, this investigation provides a comprehensive systematic review and meta-analysis of randomized controlled trials (RCTs) on the impact of CLA supplementation on anthropometric and body composition (body mass [BM], boy mass index [BMI], waist circumference [WC], fat mass [FM], body fat percentage [BFP], and fat-free mass [FFM]) markers in adults. Online databases search, including PubMed, Scopus, the Cochrane Library, and Web of Science up to March 2022, were utilized to retrieve RCTs examining the effect of CLA supplementation on anthropometric and body composition markers in adults. Meta-analysis was carried out using a random-effects model. The I2 index was used as an index of statistical heterogeneity of RCTs. Among the initial 8351 studies identified from electronic databases search, 70 RCTs with 96 effect sizes involving 4159 participants were included for data analyses. The results of random-effects modeling demonstrated that CLA supplementation significantly reduced BM (WMD: -0.35, 95% CI: -0.54, -0.15, p<0.001), BMI (WMD: -0.15, 95% CI: -0.24, -0.06, p=0.001), WC (WMD: -0.62, 95% CI: -1.04, -0.20, p=0.004), FM (WMD: -0.44, 95% CI: -0.66, -0.23, p<0.001), BFP (WMD: -0.77 %, 95% CI: -1.09, -0.45, p<0.001), and increased FFM (WMD: 0.27, 95% CI: 0.09, 0.45, p=0.003). The high-quality subgroup showed that CLA supplementation fails to change FM and BFP. However, according to high-quality studies, CLA intake resulted in small but significant increases in FFM and decreases in BM and BMI. This meta-analysis study suggests that CLA supplementation may result in a small but significant improvement in anthropometric and body composition markers in an adult population. However, data from high-quality studies failed to show CLA’s body fat-lowering properties. Moreover, it should be noted that the weight loss properties of CLA were small and may not reach clinical importance.