Overweight older adults face lower risk of death after major surgery, study shows

Older adults who are overweight faced a lower risk of death in the first 30 days after major elective surgery than those who had a body mass index (BMI) in the so-called ‘normal range’, according to new research.

The study examined surgical outcomes in patients aged 65 and older and found that being overweight – defined as a BMI between 25 and 29.9 – was associated with the lowest short-term mortality risk. Patients who had either a normal or an underweight BMI were more likely to die in the weeks following surgery.

“Traditional surgical guidelines often emphasised the need for a normal BMI before surgery, but our findings suggested that these recommendations may need to be reconsidered for older adults,” said lead author Dr Cecilia Canales, assistant professor in the Department of Anaesthesiology and Perioperative Medicine at the David Geffen School of Medicine at the University of California, Los Angeles.

“Older adults had different physiological considerations, and moderate excess weight may have been protective in the short term after surgery,” she added.

The analysis covered 414 patients treated at a large academic centre in Southern California between February 2019 and January 2022. Outcomes assessed included 30-day and one-year mortality, postoperative delirium, discharge disposition and complications.

The results showed that patients in the overweight category had a 0.8 per cent 30-day all-cause mortality rate, compared with 18.8 per cent for those of normal BMI, even after adjustment for factors such as age, frailty, comorbidities and cancer status. Underweight patients had a 15.0 per cent mortality rate within 30 days.

“This study added to a growing body of evidence of the so-called ‘obesity paradox’, where a higher BMI appeared to be linked with better survival in certain older populations,” said co-author Dr Catherine Sarkisian, professor of medicine in the Division of General Internal Medicine and Health Services Research at the Geffen School, Los Angeles.

“It was important to tailor preoperative evaluation to the physiology of older patients.”

The authors have noted that these findings may influence preoperative counselling and the BMI-based surgical risk calculators that are often derived from younger or mixed-age populations.

They have recommended further research to understand the biological and clinical mechanisms behind this association and to inform surgical guidelines for older adults.

For further reading please visit: 10.1001/jamanetworkopen.2025.28875