New research indicates low body mass index and frailty dramatically increase mortality odds following emergency surgery.
RT’s Three Key Takeaways:
- Elevated Mortality Risk: Underweight patients face 92% increased odds of death following emergency general surgery compared to those who are normal weight or overweight, according to a nationwide study.
- Compounding Impact of Frailty: Patients who are both frail and underweight experience the poorest clinical outcomes, with frailty eliminating the survival advantage typically seen in overweight patients.
- Modifiable Risk Factors: Healthcare providers can help mitigate postoperative risks through targeted interventions, including meeting protein goals, optimizing nutrition, and employing physical therapy.
Underweight patients are significantly more likely to die following emergency general surgery than patients who are normal weight or overweight, and those who are both frail and underweight face an even higher risk of mortality and adverse clinical events, according to study findings presented at the American College of Surgeons (ACS) Clinical Congress 2026.
The study analyzed data from the American College of Surgeons National Surgical Quality Improvement Program (ACS NSQIP) database, examining records from more than 334,000 adults aged 18 and older in the US who underwent emergency general surgery procedures between 2019 and 2024. The ACS NSQIP adult program includes participation from more than 600 hospitals to evaluate surgical outcomes and quality of care.
“Our study shows that patients who are both underweight and frail have the worst outcomes. We also saw that frailty reduces the positive impact of the obesity paradox — the finding that patients who are overweight, but not at the extremes of obesity, tend to have better outcomes. That protective effect is lost if a patient is frail,” said Ellen Cohn, MD, MPH, lead study author and a third-year general surgery resident at the University of Chicago, in a news release.
“What we take away from this study is that risk can be mitigated. We can make real-world changes to body mass index (BMI), and physical therapy can reduce frailty. What is unique about our study is that we were able to look at the impact of BMI and frailty together,” said Cohn in a news release.
Evaluating Frailty and Surgical Outcomes
Researchers utilized the ACS NSQIP database to evaluate the relationship between body mass index (BMI) and frailty levels on patient outcomes, including mortality, hospital length of stay, and readmission rates 30 days after initial admission, according to the presentation. Investigators assessed frailty on a scale from one to five, where one indicated a patient with a single comorbidity, such as diabetes or chronic obstructive pulmonary disease (COPD), and five designated a severely frail patient with five underlying diseases.
The analysis revealed that underweight patients faced a 92% increase in the odds of death after emergency general surgery, while patients classified as obese demonstrated better outcomes when frailty was not a factor, according to the research team.
“While the focus of our study was on underweight and frail patients, we were surprised to find that obese patients did better,” said Justin S. Hatchimonji, MD, study co-author and assistant professor of surgery in the section of trauma and acute care surgery at the University of Chicago. “I think recognizing the importance of not only underweight status, but also frailty, helps emergency general surgeons plan for postoperative outcomes and think about how to best manage these patients over the long term.”
Clinical Implications for Patient Care
According to the study authors, identifying low BMI and frailty offers acute care teams and healthcare providers an opportunity to tailor interventions to improve postoperative recovery.
“Thinking about older patients, it’s important to focus on what we can affect: nutrition, making sure protein goals are met, bone health, and vitamins,” said Cohn. “Keeping patients healthy that way can have a bigger impact on outcomes than the other comorbidities that make up the frailty score. We know that you can change underweight status and as a result get a better outcome.”
The authors noted a limitation of the study is that a large database analysis demonstrates associations rather than direct cause and effect. In addition, research abstracts presented at the ACS Clinical Congress Scientific Forum are reviewed and selected by a program committee, but the findings have not yet completed peer review.
