Incretins after bariatric surgery

A nationwide US cohort study published in EClinicalMedicine in July 2026 examined what happens when patients who have already had metabolic and bariatric surgery (MBS) go on to take incretin-based drugs. Across 208,155 post-surgical patients, those who received incretin therapy (semaglutide or tirzepatide) lost more weight. Tirzepatide produced 17.2% total weight loss versus 12.0% for semaglutide, an adjusted difference of 5.16 percentage points (95% CI 4.17 to 6.16, p < 0.001)^[1]. On the cardiovascular side, pooled incretin use was not associated with a reduction in major adverse cardiovascular events (MACE): hazard ratio 0.91 (95% CI 0.80 to 1.05, p = 0.19)^[1].

The study design

Gillikin and colleagues drew on de-identified electronic health records from 43,104 US medical centers covering 2018 to 2025. They identified 208,155 people who had undergone MBS, of whom 39,750 had received incretin-based medication postoperatively. To account for differences between who got these drugs and who did not, the team applied propensity score matching, producing matched cohorts of 35,651 incretin users and 35,651 non-users^[1]. The study is retrospective and observational: it describes what happened, not what would happen in a controlled randomised trial.

Weight loss: tirzepatide versus semaglutide

The headline weight-loss contrast is the clearest finding. In a post-surgical population that has already lost substantial weight through the procedure, tirzepatide produced 17.2% total body weight loss versus 12.0% for semaglutide at the timepoints studied^[1]. That 5.16 percentage-point adjusted difference is statistically strong. The authors also found that later initiation of incretin therapy produced better results: starting at postoperative months 53 to 79 yielded 15.4% weight loss, compared with 13.5% when therapy began in the first 12 to 24 months after surgery (p < 0.001)^[1]. Weight loss also appeared to follow a dose-response pattern across both drugs.

These numbers are meaningful because the post-bariatric population is different from the populations enrolled in the large incretin pivotal trials. Bariatric surgery already alters gut anatomy, gastric emptying, and hormone signalling. Whether drugs tested in primary obesity would work the same way in post-surgical patients was not established before studies like this one. For a broader picture of how tirzepatide compares against semaglutide in the general obesity setting, see the head-to-head trial coverage on those peptide pages.

Cardiovascular outcomes: no significant association

The cardiovascular analysis covered 884 MACE events across the matched cohorts (377 in incretin users, 507 in non-users). The pooled hazard ratio for MACE was 0.91 (95% CI 0.80 to 1.05, p = 0.19), which does not reach statistical significance^[1]. The authors concluded that incretin-based therapy in this setting was not associated with MACE risk, in either direction.

For context, bariatric surgery itself carries a documented cardiovascular benefit. A 2026 meta-analysis of 25 studies (659,517 participants) in the American Journal of Cardiology found that metabolic surgery was associated with a 45% reduction in all-cause mortality (HR 0.55), a 64% reduction in cardiovascular mortality (HR 0.36), and a 39% reduction in myocardial infarction (HR 0.61)^[2]. Against that backdrop, the post-surgical patients in the Gillikin study were already a lower-risk group than an untreated obese population, which may explain why the additional effect of incretin therapy on MACE did not register.

What the study does not settle

Several important questions remain open. First, this is a retrospective cohort study: the propensity matching reduces confounding, but it cannot eliminate it. Patients who received incretin therapy postoperatively may differ from non-recipients in ways that the statistical adjustment did not fully capture. Second, the follow-up period is tied to the electronic health record window (2018 to 2025) and does not represent a standardised observation period for each patient. Third, the study does not address what happens when the drugs are stopped. In the general obesity population, the SURMOUNT-4 discontinuation trial showed significant weight regain after tirzepatide was withdrawn; whether the same applies to post-bariatric patients is not known^[1].

The cardiovascular null finding should not be read as evidence that incretin drugs are cardiovascular-neutral in this population. The study was not powered for a MACE endpoint, and the event rate (884 events across nearly 72,000 matched patients) may be too low to detect a signal in either direction. A randomised trial would be needed to establish or rule out a cardiovascular benefit. The approved cardiovascular outcome trial for semaglutide (SELECT) and the equivalent data for tirzepatide were both conducted in primary-obesity and diabetes populations, not post-bariatric cohorts.

What this means in practice

For patients who have had bariatric surgery and are either not losing enough weight or have regained weight over time, incretin-based drugs appear to offer real additional weight loss. Tirzepatide produced meaningfully greater results than semaglutide in this dataset. The finding reinforces the pattern seen in other post-bariatric incretin studies, including a 2025 systematic review of 19 studies that reached a similar conclusion^[1].

Any decision about starting an incretin drug after bariatric surgery is off-label in most jurisdictions. Neither Mounjaro nor Zepbound (both tirzepatide) nor Ozempic or Wegovy (both semaglutide) carry a specific label for post-bariatric weight management. That decision belongs with the surgical and medical team managing the patient. Readers can check how each drug is regulated in their country via the tirzepatide regulation overview and the semaglutide regulation overview pages.