Comparative effectiveness of metabolic bariatric surgery versus incretin-based and medical therapies for weight loss and glycemic outcomes: a systematic review and meta-analysis

This project is a systematic review and meta-analysis that evaluates the comparative effectiveness of metabolic bariatric surgery versus medical and incretin-based therapies for the management of obesity and type 2 diabetes mellitus (T2D). The review synthesizes evidence from comparative clinical studies assessing outcomes related to weight reduction, glycemic control, and other metabolic parameters among adults undergoing surgical or pharmacologic treatment. The study was conducted according to PRISMA 2020 guidelines and included a comprehensive search of PubMed, Scopus, Web of Science, Google Scholar, and reference lists of relevant articles. Eligible studies directly compared metabolic bariatric surgery procedures, including sleeve gastrectomy and Roux-en-Y gastric bypass, with medical management or incretin-based therapies such as GLP-1 receptor agonists. Data extraction, risk-of-bias assessment, outcome harmonization, and quantitative synthesis were performed using predefined methods. The primary outcomes of interest were weight loss and glycemic improvement, measured through standardized analyses of body-weight change and HbA1c reduction. Secondary outcomes included fasting plasma glucose, lipid parameters, medication use, diabetes remission, and other metabolic indicators when available. Random-effects meta-analyses were conducted to account for clinical and methodological heterogeneity across studies, and subgroup analyses were performed according to treatment era, study design, and follow-up duration. The findings indicate that metabolic bariatric surgery remains associated with greater overall weight loss and improved glycemic outcomes compared with medical and incretin-based therapies, although the difference between treatment approaches has narrowed with the emergence of modern incretin-based medications. The study also explores how advances in obesity pharmacotherapy have influenced comparative effectiveness over time. This OSF project contains the supplementary materials supporting the manuscript, including the complete search strategies, outcome harmonization tables, sensitivity analyses, subgroup analyses, additional forest plots, risk-of-bias figures, and the PRISMA 2020 reporting checklist. These materials are provided to enhance transparency, reproducibility, and accessibility of the review process and findings. The expected outcome of this project is to provide a comprehensive evidence synthesis that informs clinicians, researchers, and policymakers regarding the relative benefits of surgical and pharmacologic treatment strategies for obesity and type 2 diabetes management.