Effects of conjugated linoleic acid and exercise on body composition and obesity: a systematic review and meta-analysis

Abstract

Context Conjugated linoleic acid (CLA) has been reported to have anti-obesity and antidiabetic effects. However, the benefits of CLA combined with exercise remain unclear, and studies report conflicting results. Objective A systematic review and meta-analysis were performed to investigate the synergistic effect of CLA and exercise on body composition, exercise-related indices, insulin resistance, and lipid profiles; and of the safety of CLA supplements. Data sources In October 2021, the PubMed, Embase, and Cochrane Library databases were searched for reports on clinical trials of the combined intervention of CLA and exercise. Data extraction A total of 18 randomized controlled trials and 2 crossover trials were included. The methodological quality assessment was performed using the revised Cochrane risk-of-bias tool. Pooled effect sizes were reported as standardized mean difference (SMD) for continuous data and risk ratio for dichotomous data with their corresponding 95% confidence intervals (CIs). Heterogeneity was tested using the I2 statistic. Data analysis The combination of CLA and exercise resulted in significantly decreased body fat (SMD, –0.42 [95%CI, –0.70, –0.14]; P = 0.003; I2 = 65) and insulin resistance (SMD, –0.25 [95%CI, –0.44, –0.06]; P = 0.01; I2 = 0) than did exercise alone. In subgroup analysis, the following factors were associated with significant outcomes: (1) body mass index ≥25 kg/m2; (2) female sex; (3) follow-up time >4 weeks; and (4) intervention duration >4 weeks. Nevertheless, supplementation with CLA during exercise programs was not effective for body-weight control, exercise performance enhancement, or lipid-profile improvement. CLA in combination with exercise did not result in a higher risk of adverse events (risk ratio, 1.32 [95%CI, 0.94–1.84]; P > 0.05; I2 = 0). Conclusion CLA combined with exercise is generally safe and can lower body fat and insulin resistance but does not reduce body weight, enhance exercise performance, or improve lipid profiles.

Psychological determinants of the effectiveness of conjugated linoleic acid supplementation in overweight and obese women—a randomized controlled trial

“…Also, a recent meta-analysis demonstrated an improvement in anthropometric parameters and body composition after CLA supplementation in adults ( 36 ). However, Liang et al ( 21 ), in their meta-analysis, demonstrated that CLA supplementation during exercise programs did not improve body weight but significantly reduced fat mass. Taking into account the inconsistency in the obtained results we hypothesized that psychological factors might affect the success of the CLA intervention and ability to complete the study.…”

“…However, the effect was small and did not seem clinically relevant. Contrary, Liang et al ( 21 ) in a recent meta-analysis demonstrated that CLA supplementation during exercise programs was not effective for body-weight control compared to exercise alone but significantly reduced fat mass.…”

Evaluation of reported claims of sex-based differences in treatment effects across meta-analyses: A meta-research study

“…In 7 articles (7 claims) the effect was stated to be larger in one group, but the overall differences were not statistically significant [33,[70][71][72][73][74][75]. 3 articles (3 claims) had different forms of fallacies: a p-value of 0.09 was considered significant [76];…”