The Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program Bariatric Surgical Risk/Benefit Calculator: 1-year weight

Published:December 17, 2022DOI:


      • The Bariatric Surgical Risk/Benefit Calculator estimates patient-specific 1-year BMI
      • Predicted BMI closely aligned with actual BMI values through 12-months postoperative
      • BMI, weight change, and percent total weight change are estimated for 4 procedures
      • The tool aids in surgical decision-making, communication, and informed consent



      Data-driven tools can be designed to provide patient-personalized estimates of health outcomes. Clinical calculators are commonly built to assess risk, but potential benefits of treatment should be equally considered. The American College of Surgeons Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) sought to create a risk and benefit calculator for adult patients considering primary metabolic and bariatric surgery with multiple prediction features: (1) 30-day risk, (2) 1-year body mass index (BMI) projections, and (3) 1-year co-morbidity remission.


      To assess the performance of the 1-year BMI projections feature of this tool.


      Not-for-profit organization, clinical data registry.


      MBSAQIP data from 596,024 cases across 4.5 years from 882 centers with ∼2.5 million records through 18 months postoperatively were included. A generalized estimating equation model was used to estimate BMI over time for 4 primary procedures: laparoscopic adjustable gastric band, laparoscopic sleeve gastrectomy, laparoscopic Roux-en-Y gastric bypass, and biliopancreatic diversion with duodenal switch.


      The mean absolute error (MAE) in BMI predictions through postoperative month 12 was 1.68 units; overall correlation of actual and predicted BMI was .94. MAE of postoperative BMI estimates (1–12 mo) was lowest for laparoscopic sleeve gastrectomy (1.64) and highest for biliopancreatic diversion with duodenal switch (1.99). BMI predictions at 12 months showed MAE = 2.99 units.


      Predicted BMI closely aligned with actual BMI values across the 12-month postoperative period. The MBSAQIP Bariatric Surgical Risk/Benefit Calculator is publicly available with the intent to facilitate patient–clinician communication and guide surgical decision making. This tool can aid in evaluating postoperative risk as well as benefits and long-term expectations.


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