GLP-1 use before bariatric surgery doesn’t boost postsurgical weight loss

Clinical takeaway: Preoperative GLP-1 therapy does not appear to enhance weight loss 12 months after bariatric surgery.

As GLP-1–based medications become more widely used for obesity, more patients taking them are going on to bariatric surgery. That overlap raises an increasingly relevant clinical question: Does using the drugs before surgery add to the weight loss achieved with surgery?

A retrospective study of 383 patients undergoing primary bariatric surgery found no evidence of an additive benefit. Ninety-two patients (24%) were taking a GLP-1–based medication before surgery, most commonly semaglutide.

At 12 months, patients who had used GLP-1 therapy before surgery had lost an average of 24% of their total body weight, compared with 25% among patients without preoperative use. Excess weight loss was also similar, at 60% versus 62%. After adjustment for patient characteristics, diabetes, procedure type, and other factors, preoperative GLP-1 use was not associated with 12-month weight loss.

The findings suggest that GLP-1 therapy before surgery neither improves nor compromises the substantial weight loss achieved with bariatric surgery. The groups also had similar 12-month A1c levels, operative times, hospital stays, 30-day emergency department visits, and complications.

What happens after surgery remains less certain. The study center generally recommended discontinuing GLP-1 therapy after surgery to reduce vomiting risk, and most patients remained off treatment. Only 15 resumed therapy during the following year, including eight for weight control and five for diabetes. Their weight loss was similar to that of patients not taking GLP-1 drugs, but the small number prevents conclusions about postoperative use.

Whether GLP-1–based medications can help maintain weight loss or treat weight regain after bariatric surgery therefore remains an important question. The authors said further research is needed to determine the optimal sequencing and combination of pharmacotherapy and surgery.

“Taken with our results, these data suggest that preoperative GLP-1 RAs neither augment nor detract from surgical weight loss, at least for the first 12 months postoperatively,” the authors concluded.

Source: Huynh RL, et al. (2026 Aug 12) JAMA Surg. Preoperative GLP-1 receptor agonist use and weight loss outcomes after bariatric surgery