Higher BMI linked to increased risk of complications after bariatric surgery

The higher a person's body mass index (BMI), the higher their risk for complications after bariatric surgery, especially those with BMI of 50 or more, according to a new study presented today at the American Society for Metabolic and Bariatric Surgery (ASMBS) 2025 Annual Scientific Meeting.

Researchers found that the rate of complications increased by an average of 5.56% and serious occurrences rose 3.21% from the lowest BMI category to the highest, with people with a BMI 50 or more the most likely to experience complications of any kind.

The 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," said study co-author John Scott, MD, FACS, FASMBS, Chief for the Division of Minimal Access and Bariatric Surgery for the Prisma Health Dept. of Surgery in Greenville, SC. "Obesity itself is a risk factor in surgeries of all kinds, but in bariatric surgery the risks remain relatively low."

The retrospective study involved a review of the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) database for patients with obesity (BMI 30 or more) who had either sleeve gastrectomy or Roux-en-Y gastric bypass between 2020 and 2023. A total of 665,047 cases were included.

"While complication rates are generally low, this study provides granular data not previously reported that can help with pre-operative counseling and to make surgery even safer and patient outcomes even better," said Richard M. Peterson, MD, MPH, FACS, FASMBS, President-elect, ASMBS, and Professor of Surgery, UT Health San Antonio, who was not involved in the study.