Effects of Bioactive Compound Supplementation on Insulin Resistance and Systemic Inflammation in Overweight and Obese Adults: A Systematic Review and Meta-Analysis of Randomized Controlled Trials.

Obesity is characterized by chronic low-grade inflammation, with increased expression of pro-inflammatory cytokines such as TNF- α and IL-6, and elevated systemic CRP levels, impairing insulin signaling and promoting insulin resistance. Bioactive compounds such as curcumin, green tea extract, resveratrol, and omega-3 fatty acids have demonstrated anti-inflammatory and insulin-sensitizing properties in pre-clinical models; however, evidence from human studies remains heterogeneous and inconclusive. This systematic review and meta-analysis evaluated the effect of isolated supplementation of these compounds on CRP and HOMA-IR as primary outcomes, subjected to quantitative synthesis. The target population comprised adults with overweight or obesity (BMI > 24,9 kg/m²) without a diagnosis of type 2 diabetes, including those with obesity-related metabolic comorbidities. The search was conducted in March 2026 across PubMed and Scopus. Of the 1,249 records identified, 59 RCTs were included following screening: omega-3 (n = 23), curcumin (n = 13), green tea (n = 13), and resveratrol (n = 10). Meta-analyses were performed in JASP using a random-effects model (REML, Knapp-Hartung adjustment), with mean difference (MD) as the effect size measure. Heterogeneity was assessed using the Q statistic and τ; publication bias was evaluated through visual inspection of residual funnel plots. Only curcumin demonstrated a statistically significant effect, reducing HOMA-IR compared to placebo (MD = -0.30 [-0.53, -0.07], p = 0.019), with low and non-significant heterogeneity (Q(6) = 7.53, p = 0.275, τ = 0.13). Green tea extract yielded a borderline reduction in CRP (MD = -0.44 mg/L [-0.88, 0.01], p = 0.053), accompanied by substantial heterogeneity (Q(6) = 40.34, p < 0.001, τ = 0.42). Resveratrol and omega-3 showed no significant effect on either outcome. Significant heterogeneity was observed in four of the eight final analyses. In conclusion, the findings suggest that curcumin may exert a modest but consistent effect on insulin resistance in overweight and obese adults, while the potential anti-inflammatory effect of green tea requires confirmation in methodologically more standardised studies. Interpretation of the results should account for key limitations, including heterogeneity in compound formulations and doses, the treatment of crossover trials as parallel designs, the absence of formal publication bias testing, and the small sample sizes of several included studies. Future research should prioritise randomised controlled trials with standardised formulations with documented bioavailability, particularly for curcumin and green tea, alongside meta-analyses evaluating dietary patterns naturally rich in these compounds to allow comparison between long-term dietary exposure and short-term supplementation effects, and stratified analyses by metabolic phenotype to identify subpopulations most likely to benefit from targeted bioactive compound supplementation.