Multiple randomized controlled trials (RCT), cohort studies, and case series from expert centers have demonstrated that metabolic bariatric surgery (MBS) is an effective treatment option for obesity, safely inducing not only weight loss but remission from important obesity-related diseases, including diabetes, hypertension, and cardiovascular disease [1,2,3]. How these positive results translate in the “real-world” setting remains largely unknown. There is also limited knowledge comparing the uptake and practice of MBS worldwide.

Registries use observational study methods to systematically collect uniform data, which are used to evaluate specified outcomes for a defined population [4]. In the field of MBS, these registries can be used to record the characteristics of the population undergoing MBS, document the types of procedures being performed, capture the safety of surgery through the prospective recording of quality indicators, and track the weight loss, health, and patient-reported outcomes of MBS. There are thirty known national and two complete regional MBS registries, each with an emerging dataset, with some having been shown already to improve outcomes for patients [5].

The International Federation for Surgery for Obesity and Metabolic Disorders (IFSO) has sought to drive collaborations between existing registries so that the positive outcomes achieved by individual registries may be translated globally. IFSO has also sought to help establish registries in other member countries that do not currently have a local registry. The Executive Board of IFSO established the IFSO Global Registry to facilitate these dual goals.

The IFSO Global Registry's mission is to provide the most credible and transparent information on MBS. To achieve this mission, the IFSO Global Registry aims to provide descriptive data about caseload and penetrance of surgery for metabolic disease and obesity in member countries and aspire to provide real-world surveillance of procedures and devices.

The first IFSO Global Registry report was produced in 2014. In that report, information was included from 18 countries coming from 5 continents that contributed 100,092 operation records, with 53,197 between the calendar years 2011–2013. The number of operations contributed ranged from one individual center that had entered 24 operation records to over 34,000 each from two countries with established national registries (Sweden and the United Kingdom).

Over time, contributions to the IFSO Global Registry have grown, and by the sixth report, there were 507,298 operations submitted by 50 contributor countries, 10 of whom were national or regional registries. However, including individual-level data from each contributing site created significant challenges for IFSO, particularly with the rigorous standards of data protection required by the General Data Protection Regulations (GDPR).

In 2022, the IFSO Global Registry Committee proposed to the Executive Board of IFSO that future reports include only aggregated data from established national or regional registries using a data dictionary focusing on demographic and descriptive data only. Outcome data was not included as it was inconsistently collected by registries worldwide, making comparisons difficult.

“Aggregated data” means that the data given to the IFSO Global Registry is already analyzed and provided as a mean or a median, meaning individuals cannot be identified. As no individual-level data transfer is required, there is no risk of a GDPR privacy breach. By only including data from national or complete regional registries, selection bias is reduced, making it more likely that the IFSO Global Report accurately represents the activity of an included country or region.

This is a summary of the key findings of the eighth report of the IFSO global registry and the second to contain only aggregated data from established national and regional registries [6].