The effect of intermittent fasting on insulin resistance, lipid profile, and inflammation on metabolic syndrome: a GRADE assessed systematic review and meta-analysis.

Background: Evidence revealed that fasting intervention may have favorable effects on metabolic and inflammation profile. However, the results are controversial. This study attempted to investigate and assess the effects of fasting on cardiometabolic risk factors in adults.

Methods: We searched PubMed, Embase, Cochrane, Scopus, and Web of Science databases until March 2025 for randomized controlled trials (RCTs) which have evaluated the effect of fasting intervention on metabolic and inflammation profile. The GRADE approach was applied to assess the quality of evidence, and the Cochrane risk-of-bias (RoB) 2 tool was used to evaluate study quality.

Results: Eight RCTs with 573 participants were included in the meta-analysis. Findings revealed that fasting could significantly decreased fasting blood glucose (FBS) (WMD = -3.34; 95% CI: -6.24, -0.45, P = 0.024), HbA1c (WMD = -0.08; 95% CI: -0.13, -0.02; P = 0.005), and HOMA-IR (WMD= -0.60; 95% CI: -0.91, -0.28; P < 0.001) in adults. Similarly, fasting intervention exerted its favorable effect by reducing low-density lipoprotein cholesterol (LDL-c) (WMD = -6.42; 95% CI: -12.26, -0.58; P = 0.031), and IL-6 (WMD = -0.58; 95% CI: -1.08, -0.08; P = 0.022), significantly. The sensitivity analysis, indicated that excluding any single study has no effect on the overall effect size. No evidence of publication bias was observed using Begg's test (P > 0.05).

Conclusion: Overall this systematic review and meta-analysis demonstrated that fasting state contributed to improved glycemic control including FBS, HbA1c, and HOMA-IR levels. In addition, fasting intervention caused to an improvement in lipid metabolism (LDL-c) and inflammatory state indicated by IL-6.