September 09, 2026
3 min read
Key takeaways:
- GLP-1 users and nonusers achieved comparable total body weight loss 1 year after bariatric surgery.
- Diabetes control and postsurgical complications also were similar between groups.
Preoperative GLP-1 receptor agonist use did not impact bariatric surgery outcomes, including weight loss at 1 year, diabetes control and postsurgical complications, according to a research letter published in JAMA Surgery.
GLP-1s have become an integral part of obesity care, but clinicians still have questions about how pharmacologic therapy and surgical intervention interact.
“Since the most effective treatment for obesity remains bariatric surgery, many have wondered how best to combine bariatric surgery with GLP-1 RAs and whether being on a GLP-1 RA affects the results of subsequent surgery,” study author Jonathan Carter, MD, bariatric surgeon and professor of surgery at UCSF Medical Center, told Healio.
Carter and colleagues conducted a retrospective analysis of 383 patients who underwent bariatric surgery at UCSF between 2022 and 2024.
Before surgery, 92 patients (mean age, 44 years; 78% women; baseline BMI, 43 kg/m2) had initiated GLP-1 therapy, the most common of which was semaglutide, and 291 had not (mean age, 44 years; 80% women; baseline BMI, 44 kg/m2 ). Those taking GLP-1s were advised to discontinue use after surgery to mitigate risk for vomiting.
The majority of patients in both groups underwent sleeve gastrectomy (83% of GLP-1 users and 88% of nonusers) vs. gastric bypass.
Total body weight loss percentage at 1 year served as the primary outcome. Secondary outcomes included surgical complications and postoperative HbA1c.
According to results, total body weight loss at 1 year was comparable between GLP-1 users and nonusers (mean, 24% vs. 25%), as was excess body weight loss (mean, 60% vs. 62%), and did not reach statistical significance.
Differences between groups in operative time, length of hospital stay, ED visits within 30 days of surgery and surgical complications also were not statistically significant.
Multivariable analysis — adjusted for age, sex, race/ethnicity, BMI and diabetes, among other factors — showed preoperative GLP-1 use did not predict total body weight loss at 1 year (beta=0.17).
“Given that one mechanism of how bariatric surgery works is via GLP-1 augmentation, I thought that weight loss in patients on GLP-1s taken preoperatively might ‘steal’ from the weight loss we see later with surgery,” Carter said. “In our study, we saw no such effect.
“Those taking GLP-1s, who presumably lost weight from the medications before surgery, turned out to lose additional weight the same as the GLP-1-naive patients,” he added.
Diabetes control “was excellent in both groups,” according to the researchers, with 1-year HbA1c levels of 5.4% and 5.3% for GLP-1 users and nonusers, respectively.
Carter and colleagues identified independent associations between greater total body weight loss at 1 year and higher baseline BMI (beta=0.29; P <0.001) and male sex (beta=2.67; P =0.014). Lower total body weight loss was independently associated with diabetes (beta=4.49; P <.001) and sleeve gastrectomy (beta=4.72; P <.001).
Among the 15 GLP-1 users who resumed treatment postoperatively, total body weight loss at 1 year was similar to that of patients who did not take GLP-1s (mean, 22% vs. 25%).
The study had several limitations, including lack of data on duration of GLP-1 use prior to surgery, as well as preoperative weight loss attributable to GLP-1s.
“Ours was a single-center study of patients mostly on semaglutide, and very few were on tirzepatide,” Carter said. “The data on this question will evolve over time with larger studies, newer drugs and a better understanding of how much weight was lost at medicine initiation and then [with] surgery.”
Future studies should investigate optimal methods to combine and sequence pharmacological and surgical aspects of obesity therapy to maximize weight loss, according to the researchers.
“Patients on GLP-1s can go on to have terrific results with bariatric surgery to lose additional weight,” Carter told Healio. “In other words, it is not a zero-sum game; the weight loss of GLP-1s and then bariatric surgery seems to be additive.
“We should not think of obesity treatment as a competition between medicine and surgery. Rather, combination therapy is proving to be the best for our patients.”
For more information:
Jonathan Carter, MD, can be reached at jonathan.carter@ucsf.edu.
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