Abstract
Background: Type 2 diabetes mellitus (T2DM) is a growing global health challenge requiring effective dietary management strategies. While the Mediterranean diet shows promise for cardiovascular and metabolic health, the last comprehensive meta-analysis of randomized controlled trials (RCTs) examining its effects on glycemic control and body mass index (BMI) in T2DM was published in 2015. Multiple RCTs, including culturally adapted interventions with extended follow-up, have since been completed, but remain unsynthesized. Methods: We conducted a systematic review and meta-analysis following PRISMA 2020 guidelines (PROSPERO: CRD420251147035), searching PubMed, Web of Science, and Embase from inception through 17 August 2025. Unlike previous syntheses that combined observational cohorts or mixed dietary approaches, our analysis focused strictly on RCTs in adults with established T2DM and incorporated trials published after 2015. We included RCTs comparing Mediterranean diet interventions against non-Mediterranean control diets in adults with T2DM. Primary outcomes included glycated hemoglobin (HbA1c), fasting plasma glucose (FPG), and body mass index (BMI). Secondary outcomes comprised low-density lipoprotein cholesterol (LDL-C), systolic blood pressure (SBP), and diastolic blood pressure (DBP). Pooled effects were estimated using random-effects models. Results: Eleven RCTs (10 publications) involving diverse populations met inclusion criteria. Compared with control diets, Mediterranean diet interventions showed reductions in HbA1c (mean difference [MD] -0.307%, 95% CI: -0.451 to -0.163), FPG (MD -0.845 mmol/L, 95% CI: -1.307 to -0.384), and BMI (MD -0.828 kg/m(2), 95% CI: -1.4 to -0.256). Secondary analyses revealed reductions in LDL-C (MD -8.060 mg/dL, 95% CI: -14.213 to -1.907), SBP (MD -5.130 mmHg, 95% CI: -10.877 to 0.617), and DBP (MD -2.008 mmHg, 95% CI: -3.027 to -0.989). Sensitivity analyses supported stability of findings, with no substantial publication bias detected. Subgroup analyses revealed geographic variation in blood pressure responses, with greater benefits observed in non-Mediterranean populations. Conclusions: Mediterranean dietary patterns were associated with modest improvements in glycemic control, body composition, and cardiometabolic risk factors among adults with T2DM. The cultural adaptability of this approach may support implementation in clinical practice, though larger multicenter trials with standardized protocols and extended follow-up remain necessary.