Effect of Low/Very Low-Calorie and Other Special Diets on Anthropometric and Cardio-Metabolic Parameters of Diabetes Mellitus Patients: A Systematic Review and Meta-Analysis

Introduction and Methodology: This systematic review and meta-analysis, following PRISMA guidelines and registered in PROSPERO (CRD42025645593), searched Embase, Scopus, PubMed, Web of Sciences and Google Scholar for studies on low-calorie or very-low-calorie or other special diets (VLC/KD) in diabetes mellitus (DM) patients. Results: From 16 RCTs involving 1232 patients, the meta-analysis found reductions with standardised mean difference in weight (-0.59; 95% CI, -1.05: -0.13), waist (-0.72; 95% CI, -1.80: 0.37), BMI (-0.93; 95% CI, -1.56; -0.29), Hba1c (-0.67; 95% CI, -0.94: -0.40), fasting (-0.82; 95% CI, -1.35: -0.29) and post-prandial blood sugar (-0.45; 95% CI, -4.06: 3.16), Total cholesterol (-0.37; 95% CI, -0.76: 0.03), LDL cholesterol (-0.16; 95% CI, -0.45: 0.14), HDL cholesterol (0.19; 95% CI, -0.03: 0.41), systolic blood pressure (-0.55; 95% CI, -0.89: -0.22), and diastolic blood pressure (-0.52; 95% CI, -0.92: -0.13) after a long-term intake of low/very-low calorie or other special diets. High heterogeneity (I² >50%) was observed in most outcomes, warranting cautious interpretation. Conclusions: These results support incorporating high-fibre, low-glycemic index foods and Monounsaturated Fatty Acids (MUFA) over Saturated Fatty Acids in energy-balanced diets for DM management.