The Anti-Inflammatory Effects of Resistance Training in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis

Type 2 diabetes mellitus (T2DM) is associated with increased cardiovascular risk characterized by low-grade inflammation. The aim of this systematic review and meta-analysis was to assess the effects of resistance exercise training (RET) predominantly on cytokines, along with changes in glucose profile and body composition in T2DM patients. The present systematic review and meta-analysis was conducted utilizing PubMed, Web of Science, Embase, and the Cochrane Library databases from their inception up to July 2024 (PROSPERO; registration number CRD420251149352). We screened only for randomized controlled trials investigating the effects of systematic, supervised RET on C-reactive protein (CRP) and adipokines: adiponectin, interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), along with changes in anthropometric indices and glycemic control in adult T2DM patients. Pooled post-exercise weighted mean differences (WMDs) with 95% confidence intervals (CIs) were calculated for all outcomes of interest between exercise-treated patients and controls. Sixteen studies involving a total of 668 T2DM patients were retrieved from the databases for meta-analysis. We used the GRADE framework for assessing the certainty of evidence. Cochran Q-score (I²) was used to estimate heterogeneity among studies (level of significance p < 0.10) and risk of bias analysis was also performed. The cumulative results showed that post-RET inflammatory markers were lower in exercise-treated patients compared to controls regarding CRP (mg/L) (WMD: −0.63; 95%CIs: −1.05, −0.20; p < 0.001); adiponectin (μg/mL) (WMD: −0.94; 95%CIs: −1.49, −0.38; p < 0.001). The results from adiponectin are quite conflicting since they derived from only three studies, where one of them had the greater impact. In parallel, we noticed significant amelioration of fasting glucose and HbA1c (p < 0.001), while body weight remained unaltered. Our meta-analysis demonstrated non-significantly lower levels of IL-6 and TNF-α in RET vs. control group. RET can merely reduce the inflammatory burden in T2DM patients by ameliorating the circulating levels of CRP and adiponectin, while in the rest of the biomarkers, non-significant results were obtained. Hence, the overall clinical impact of those anti-inflammatory effects of RET needs to be determined.