Population Meeting Surveillance-Based Thresholds for Metabolic and Bariatric Surgery Evaluation under the 1991 NIH and 2022 ASMBS/IFSO Criteria Across 37 Settings: STEPS Analysis and Projections to 2030

Background Updated recommendations for metabolic and bariatric surgery may expand the population requiring further clinical evaluation, but their scope across settings remains unclear. We estimated adults aged 18–69 years meeting a restricted surveillance-based operationalization of the 1991 US National Institutes of Health (NIH) and 2022 American Society for Metabolic and Bariatric Surgery/International Federation for the Surgery of Obesity and Metabolic Disorders (ASMBS/IFSO) thresholds through 2030. Methods This was an observational burden-estimation and population-projection study based on secondary analysis of cross-sectional surveys. We analyzed World Health Organization (WHO) STEPwise Approach to Noncommunicable Disease Risk Factor Surveillance (STEPS) surveys from 37 settings. Estimates incorporated the complex survey design, demographic projections, paired primary-sampling-unit bootstrap resampling, and Shapley decomposition. The 2030 demographic-stability scenario was primary; the epidemiological-trend scenario was exploratory. Results We analyzed 138,695 participants, representing 468.2 million adults in 2030. In the common classifiable universe, 17.1 million (3.6%) met the operationalized NIH threshold and 48.5 million (10.4%) met the ASMBS/IFSO threshold, a paired ratio of 2.84. The additional 31.5 million comprised 26.5 million with body mass index (BMI) 30.0–34.9 kg/m2 and metabolic disease and 4.9 million with BMI 35.0–39.9 kg/m2 outside the NIH threshold stratum. Threshold prevalence was higher among women and older adults and varied across settings. In the high/exploratory scenario, 64.2 million met the ASMBS/IFSO threshold, and epidemiological change accounted for 51.7% of the projected increase. Conclusion The restricted surveillance-based operationalization of the ASMBS/IFSO thresholds identified a population nearly three times larger than the NIH threshold stratum. These estimates quantify a population requiring further clinical evaluation and capacity planning; they do not establish individual candidacy, indication, or expected utilization.