Surgery vs semaglutide and tirzepatide

A retrospective study of 44,025 adults associated sleeve gastrectomy and gastric bypass with substantially more weight loss than injectable semaglutide or tirzepatide. At one year, adjusted total weight loss was 5.4% with semaglutide and 9.1% with tirzepatide, compared with 24.4% after sleeve gastrectomy and 29.8% after gastric bypass^[1]. This was an analysis of health records, not a randomized comparison. It shows an association under routine care and cannot prove that choosing surgery would produce the same difference for any particular person.

How the comparison was built

The researchers studied adults with a body mass index of at least 35 at two urban health systems between 2018 and 2024. Some received injectable semaglutide or tirzepatide. Others underwent sleeve gastrectomy or gastric bypass. They used inverse probability weighting, a statistical method intended to make unlike treatment groups more comparable, and mixed linear models to estimate weight change over time^[2]. The four groups were large: 25,804 semaglutide recipients, 7,308 tirzepatide recipients, 8,728 sleeve patients, and 2,185 gastric-bypass patients.

The main analysis followed an intention-to-treat idea: a medication recipient remained in the assigned group even if later orders were not continuous. The authors also ran a per-protocol analysis limited to people with one year of continuous GLP-1 medicine orders^[1]. In a records study, an order is not the same as confirmed dispensing or use. The continuous-order analysis is useful, but it still does not measure every injection taken.

What happened over time

Semaglutide was associated with 5.4% total weight loss at one year, 6.5% at two years, and 7.4% at three years. Sleeve gastrectomy estimates were 24.4%, 22.4%, and 22.0% at those same time points. Gastric bypass estimates were 29.8%, 28.1%, and 28.4%^[1]. The surgical estimates remained far larger through three years, although the gap is a comparison among treated groups rather than a randomized treatment effect.

Tirzepatide was associated with 9.1% total weight loss at one year and 10.8% at two years. The abstract does not report a three-year tirzepatide estimate. That absence matters because tirzepatide entered routine use later in the study period, leaving less long-term follow-up than for the other options^[2]. A missing three-year estimate should not be filled in by extending the two-year trend.

Among people with a full year of continuous medicine orders, estimated weight loss was higher than in the main medication analysis. Semaglutide estimates were 7.2%, 8.0%, and 8.8% across years one through three. Tirzepatide estimates were 11.7% at one year and 11.9% at two years^[1]. Even in that selected group, the averages remained below the surgical estimates.

Why this is not a treatment ranking

People who receive surgery differ from people prescribed a medicine in ways that health records and statistical weighting may not fully capture. Referral patterns and willingness to undergo an operation can influence treatment selection. Insurance access and contraindications matter too. So do dose escalation, side effects and limited persistence. Those factors can affect what weight measurements later appear in the record. Residual confounding, meaning unmeasured differences left after adjustment, remains possible.

The paper reports effectiveness under routine care, while tightly controlled efficacy trials answer a different question. That distinction is basic. It also compares weight outcomes, not the complete balance of surgical complications and medicine adverse effects. Costs, access, follow-up needs and individual medical goals sit outside the headline percentages. The PubMed record classifies the paper as a comparative journal study, not a randomized clinical trial^[1]. Readers should not turn the averages into a self-directed choice between an operation and a prescription.

The percentages also should not be used to compare safety. Surgery creates an immediate procedure and recovery period, followed by long-term nutritional monitoring. Prescription treatment has its own adverse-effect profile and depends on continued access and use. Our semaglutide safety summary and tirzepatide safety summary cover medicine-specific evidence, while the US semaglutide regulation page and US tirzepatide regulation page explain prescription status. Those pages provide context, but none can replace an assessment of surgical eligibility and coexisting illness. Prior treatment matters, as does the support available for follow-up. A larger average change in one outcome does not settle those separate questions. It cannot.

What we don't yet know

The accessible record does not establish why each treatment was selected, how medication doses changed, how reliably prescriptions were used, or how outcomes differed across clinically important subgroups. Tirzepatide also lacks the three-year estimate reported for semaglutide and both operations. Longer follow-up with detailed exposure data could clarify durability and discontinuation. It could also show how treatment switching helps explain differences between routine-care and trial results.

The practical conclusion is narrow. In two urban health systems, bariatric surgery was associated with more average weight loss than semaglutide or tirzepatide among adults eligible for the compared options^[2]. It does not identify the right option for an individual. That decision requires a clinician who can weigh operative risk against medicine safety, then consider access and the person's treatment priorities.

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