The Effect of Resistance, Aerobic, and Concurrent Aerobic and Resistance Exercises on Inflammatory Markers of Metabolically Healthy Overweight or Obese Adults: A Systematic Review and Meta-analysis.

Objectives: To compare the effectiveness of different exercise interventions on improving adiposity-related inflammatory markers of metabolically healthy obese (MHO) adults.

Methods: This is a systematic review with meta-analysis of randomized controlled trials (RCTs) and quasi-experimental studies on the effects of exercise interventions in the inflammatory markers of sedentary adults with MHO phenotype. Systematic searches were performed in PubMed, Cochrane, CINAHL, and OVID from January 2021 to January 2022. The included studies were from 2000 to 2021. The inclusion criteria included: a) adults with obese phenotype, b) has physical activity or exercise as intervention, and c) inflammatory markers as outcome measure. Exclusion criteria included: a) pregnant women, b) adults with cardiovascular conditions or taking medications, c) participants having central obesity. The review was registered on PROSPERO (CRD42021249661). Risk of bias (RoB) assessment was performed using Revised Cochrane RoB tool for RCTs, and ROBINS-I tool for quasi-experimental studies. A meta-analysis was performed for inflammatory markers and body composition measurements using random effects model with forest plots presenting mean differences (MD) of outcome measures with 95% CI.

Results: Twenty-one RCTs and seven quasi-experimental studies with 1,117 participants were included in the review. For short-term intervention, aerobic exercises showed an increased trend in IL-6 levels, and both resistance and aerobic exercises reduced TNF-alpha and CRP levels, respectively. For long-term exercises, aerobic exercises showed a significant reduction in CRP (MD= -0.33, 95%CI, -0.57 to -0.09, p=0.006). Long-term concurrent training also showed a significant reduction in TNF-alpha (MD= -2.65, 95%CI, -4.13 to -1.18; p=0.0004). Meta-regression also found no direct association between body weight and fat mass, and changes in inflammatory markers.

Conclusion: Concurrent and aerobic exercises were both effective in reducing pro-inflammatory markers. Concurrent training was more effective in reducing BMI, body fat composition, and CRP compared to aerobic and resistance exercises. Furthermore, middle-aged women benefited from aerobic exercises to reduce IL-6 levels. These results indicate the need for both resistance and aerobic exercise in improving inflammatory levels of the body. This review has limitations in terms of degree of heterogeneity brought by different exercise protocol and assessment of inflammatory markers. More research is needed to identify possible outcome measures that can predict chronic inflammation in MHO people.