New research presented at the 2025 Annual Scientific Meeting of the American Society for Metabolic and Bariatric Surgery (ASMBS) shows that individuals with a higher body mass index (BMI)—especially those with a BMI of 50 or more—face a greater risk of complications following bariatric surgery.
The study reviewed more than 665,000 cases from the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database. It focused on patients with obesity (BMI 30 and above) who underwent either sleeve gastrectomy or Roux-en-Y gastric bypass between 2020 and 2023.
The findings showed a clear trend: as BMI increased, so did the risk of complications. From the lowest to the highest BMI categories, overall complication rates rose by an average of 5.56%, while serious complications increased by 3.21%. The risk of experiencing any kind of complication was highest among those with a BMI of 50 or greater.
Dr. John Scott, co-author of the study and Chief of the Division of Minimal Access and Bariatric Surgery at Prisma Health in South Carolina, explained that the data helps pinpoint the BMI level at which risks begin to significantly rise.
“This study gives new insights into the risks associated with each BMI category and identifies the inflection point for increased risk of morbidity and mortality, which occurs when patients pass BMI 50,” he said. “Obesity itself is a risk factor in surgeries of all kinds, but in bariatric surgery the risks remain relatively low.”
Although bariatric surgery is widely considered safe and effective, especially when performed by experienced surgical teams, understanding how BMI affects outcomes is essential.
According to the researchers, these findings can improve how surgeons counsel patients before surgery and may help reduce risks even further by tailoring preoperative care for those in the higher BMI ranges.
Dr. Richard M. Peterson, ASMBS President-elect and Professor of Surgery at UT Health San Antonio, who was not involved in the research, emphasized the value of the study: “While complication rates are generally low, this study provides granular data not previously reported that can help with preoperative counseling and to make surgery even safer and patient outcomes even better.”
This study highlights the importance of continued monitoring and personalized surgical planning, particularly for patients with severe obesity.
While bariatric surgery remains a vital tool for managing obesity and improving long-term health, these new insights allow for a clearer understanding of surgical risks based on BMI—and open the door to more targeted strategies to improve patient care and safety.
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