Meta-analysis: liraglutide and semaglutide yield about 9% weight loss after bariatric surgery

A systematic review and meta-analysis published August 25, 2026 in Frontiers in Endocrinology found that adults who started an incretin receptor agonist at least one year after metabolic bariatric surgery lost an additional 9.22% of their body weight at 12 months on liraglutide and 9.02% on semaglutide ^[1][2]. At six months, tirzepatide produced a mean difference in total weight loss of 4.23 percentage points in its favor compared with semaglutide ^[1][2].

How the review was done

The authors searched PubMed, Scopus and Web of Science in June 2025 for original studies of liraglutide, semaglutide or tirzepatide in adults whose bariatric surgery was at least one year before drug treatment began ^[1]. They included 27 papers in the review and pooled 19 of them in the meta-analysis ^[1][2]. The review protocol was registered with PROSPERO, an international database of prospectively registered reviews ^[1].

One detail shapes how the numbers should be read: weight loss was calculated from body weight at the start of drug treatment, not from weight before surgery or from the lowest weight reached after surgery ^[1]. The reported percentages are therefore the additional loss during pharmacotherapy ^[1].

On safety, the abstract reports no serious adverse events. Most side effects that were reported were non-serious, consisting mainly of mild gastrointestinal symptoms ^[1][2].

What the review says about expectations

For context, the review notes that in the broader obesity population — trials that excluded people who had undergone bariatric surgery — semaglutide at 2.4 mg weekly produced roughly 15% body weight reduction, and tirzepatide at 15 mg weekly about 21% ^[1]. The authors state that surgery was a prespecified exclusion criterion in randomized controlled trials of these drugs while they were being developed, which is why most evidence in the post-surgery group comes from smaller trials, case-controlled studies and case series ^[1].

The authors also flag substantial heterogeneity across the included studies — in patient characteristics, type of bariatric surgery, how weight was assessed, time since surgery and drug dosing — and say the findings should be interpreted with caution ^[1]. Most studies did not report outcomes by type of surgery, which the authors describe as a considerable source of variability, since weight loss and the likelihood of a suboptimal response depend heavily on the procedure performed ^[1].

Why it matters for patients

The review addresses a common situation: an estimated 15% to 35% of patients do not meet weight-loss targets after bariatric surgery, and 25% to 35% regain significant weight within two to five years ^[1]. The authors describe incretin receptor agonists as a possible option in those cases and suggest the drugs may serve as an alternative to a second, revisional operation ^[1][2].

That last point has limits. The suggestion that drug treatment could substitute for revisional surgery is the authors' interpretation, not a finding tested against surgery in a head-to-head trial ^[1]. The review also does not report whether the tirzepatide-versus-semaglutide comparison rests on randomized trials or on observational studies ^[1].

For anyone weighing these drugs after surgery, the practical takeaway from this analysis is a range of added weight loss in the high single digits at one year for liraglutide and semaglutide, with individual results varying widely across the studies pooled ^[1].

What has not been established

Several questions are not answered in this review. Weight-loss results beyond 12 months of treatment are not reported ^[1]. How results differ by specific procedure is not established, since most included studies did not break outcomes out by surgery type ^[1]. The review also excluded anyone who started drug treatment within one year of surgery, so it says nothing about that timing ^[1]. Whether these drugs reduce the need for repeat surgery has not been tested in a randomized trial, according to the review ^[1]. No new trial or regulatory milestone tied to this analysis has been announced ^[1][2].