Efficacy of different types of intermittent fasting in improving glycemic control in adults with overweight or obesity: a systematic review and network meta-analysis

Intermittent fasting (IF) aids the management of obesity and impaired glucose homeostasis, although the comparative efficacy of different modes of IF on glycemic control remains unclear. The current review therefore aimed to investigate the efficacy of a range of IF regimes on glycemic control in individuals with overweight and obesity. A comprehensive search was conducted in the main databases including PubMed, Web of Science and Scopus from inception to March 2025 using the three groups of keywords including “intermittent fasting”, “glycemia”, and “obesity”. Eligible studies were those investigating any mode of IF including time restricted eating (TRE), alternate day fasting diet (ADF), or the 5:2 diet compared either of caloric restriction (CR) or a non-intervention control (CON) on at least one glycemic control outcomes, including fasting glucose, fasting insulin, insulin resistance, or HbA1c (%). Standardized mean differences (SMD) or weighted mean differences (WMD) with 95% confidence intervals (CIs) were calculated using random effect model for network meta-analysis. Thirty-eight studies including a total of 3,237 overweight or obese participants were included in the meta-analysis. Compared with a CON, TRE resulted in a larger reduction in fasting glucose [WMD: -0.22 mmol/L (95% CI -0.36 to -0.08), p = 0.001], insulin resistance [SMD: -0.56 (95% CI -1.04 to -0.08), p = 0.02], HbA1c (%) [WMD: -0.25% (95% CI -0.44 to -0.05), p = 0.01]. Additionally, ADF resulted in a greater reduction in insulin resistance [SMD: -0.78 (95% CI -1.50 to -0.06), p = 0.03] and insulin [SMD: -0.57 (95% CI -1.15 to 0.001), p = 0.05]. Compared with CER, neither of the IF modes significantly reduced fasting insulin. IF can be a powerful approach to improve insulin sensitivity and glucose homeostasis in adults with excess weight, with TRE and ADF being the most effective approaches.