Trends and evolution of metabolic bariatric surgery over a decade: analysis of IFSO global registry reports' data collection, clinical trends, and a FAIR-informed appraisal of report-level transparency.

Background: The global burden of obesity continues to rise, and metabolic and bariatric surgery is the most effective intervention for durable weight loss and improvement of obesity-related diseases. The International Federation for the Surgery and Other Therapies for Obesity (IFSO) Global Registry was established in 2013 to provide standardised, multinational surveillance of MBS. No longitudinal synthesis of the successive IFSO Global Registry reports has been undertaken. Methods: We performed a retrospective secondary analysis of all nine IFSO Global Registry reports published from 2014 to 2024; all source reports were accessed on October 18, 2025. Following RECORD principles, we prespecified core domains, harmonised definitions across editions, and documented transformations in a reproducible extraction log. Report-level patterns were described for registry participation, procedure volumes and mix, operative approach, patient demographics, perioperative outcomes, and methodological evolution. A FAIR-informed appraisal of report-level transparency was conducted using a pragmatic, registry-oriented rubric. Because the registry underwent a structural transition from individual-level or mixed reporting to aggregated national reporting between the sixth and seventh editions, analyses were structured into two non-equivalent reporting eras: Reports 1-6 and Reports 7-9. Cross-era comparisons were therefore interpreted as descriptive contrasts shaped by reporting architecture, rather than as continuous epidemiological trends. Findings: Reported metabolic and bariatric surgery activity ranged from 100,092 operations across 18 countries in the First Report to 598,736 operations across 36 countries in the Ninth Report, with the highest submitted volume in the Fifth Report. These values reflect changing contributor networks and reporting frameworks and should not be interpreted as directly comparable estimates of global procedural incidence. Within submitted primary-procedure data, Sleeve gastrectomy increased from 22.0% in the First Report to 60.4% in the Ninth Report, while Roux-en-Y gastric bypass decreased from 66.0% in the First Report to 29.7% in the Ninth Report; adjustable gastric banding became uncommon, and one-anastomosis gastric bypass accounted for 4-7% where reported. Median age and body mass index were broadly stable, and Female patients represented 71.3-79.5% of patients in reports with comparable sex reporting. Revisional procedures showed higher rates of unplanned reoperation, intensive care unit admission, readmission, and mortality than primary procedures. Report-level Findable, Accessible, Interoperable, and Reusable transparency scores improved modestly, mainly through gains in findability and accessibility, while interoperability and reusability remained limited. Interpretation: Across successive public reports, sleeve gastrectomy became the most frequently reported primary procedure within submitted registry data, with substantial regional heterogeneity and important limitations in cross-edition comparability. Further harmonisation of definitions, improved follow-up completeness, and privacy-preserving access to more granular data would enhance the registry's value for benchmarking, policy, and patient-level research. Funding: No specific funding was received for this study.