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Study analysis · BMC Medicine · 2026

Surgery beats the weight loss drug: Sleeve gastrectomy leads to nearly 29% weight loss vs. 11% for semaglutide after one year—and 32% of people who stop the drug regain all the weight.

Sleeve gastrectomy surgery causes much more weight loss than the popular injection semaglutide, and when people stop the drug, many gain the weight back.

Reading level
Low certainty
Level 2b · Individual cohort studyAssociation, not causationNo causal claims

Overview

What the study found

The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.

In simple terms

This study is like watching two groups of people who chose different ways to lose weight – one group had surgery, the other took medicine. Because the people got to pick their own treatment (not assigned by chance), we can't be sure that the difference in weight loss was caused by the treatment. We can say that one treatment was linked to more weight loss, but we can't say it caused it.

What’s the bottom line?

This study compared two treatments for obesity: a stomach-shrinking surgery (sleeve gastrectomy) and a weekly injection drug (semaglutide).

How strong is this study?

The researchers planned the study well and tracked people over time, which is good. But because they didn't use a lottery to decide who got which treatment (they let people choose), there might be other reasons – like how motivated someone is – that affected the results. Also, the groups were small and from just one hospital, so we should be careful about applying these findings to everyone.

Reporting

40 / 100

  • COI disclosure+40/40
  • Data availabilitydata not shared
  • Code availabilitycode not shared
Methodology

20 / 100

  • Randomizationnot randomized
  • Blindingnot blinded
  • Control groupno control group
  • Sample size (n=71)+6.0/20
  • Follow-up+10/10
Publication

100 / 100

Statistical

46 / 100

  • P-values+15/15
  • Effect sizeno effect size reported
  • Confidence intervalsno confidence intervals
  • Pre-registration+15/15

Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.

Where it sits

RCT reviews

Max 100

Randomized Trials

Max 90

Reviews of Cohort Studies

Max 85

Cohort Studies

Max 72

Reviews of Case-Control Studies

Max 63

Case-Control Studies

Max 58

Cross-Sectional & Case Series

Max 50

Expert Opinion

Max 5
StrongerWeaker
Cohort Studies
Level 2b
47

47 / 100

Probability of being correct

Groups of people are followed over time to see who develops an outcome. Strong for identifying risk factors and associations, but cannot prove causation as firmly as RCTs.

This design cannot establish causation — the findings describe an association, not a cause. Non-randomized design; no blinding; allocation by shared decision-making introduces selection bias; baseline differences in HbA1c and triglycerides between groups; per-protocol analysis may introduce attrition bias.

No Conflicts

No conflicts of interest identified

Not Disclosed

No conflicts of interest declared and no funding statement provided.

Undisclosed — Suspicious

The study text does not include a conflict of interest section or funding disclosure. The study appears to be an independent academic study.

Key takeaways

  1. 01

    After one year, people who had surgery lost 28.6% of their body weight, while those on the drug lost only 11.3%.

  2. 02

    Surgery also improved cholesterol levels more.

  3. 03

    But when people stopped the drug, many regained weight.

  4. 04

    The surgery was much more effective for weight loss and lasting results, but it's more invasive.

  5. 05

    The drug works while you take it, but stopping often leads to weight regain.

Surprising findings

  • Despite being less effective overall, semaglutide still produced 18.5% weight loss at 6 months, matching results from large clinical trials.Many assume real-world results are worse than trials, but this study found similar effectiveness for semaglutide during the active treatment phase.
  • Almost half (44.4%) of surgery patients reported GERD symptoms at 6 months, compared to 20% on the drug.Surgery is often thought to improve GERD, but this study suggests it might worsen it. However, baseline GERD was not measured, so this finding is uncertain.

Practical takeaways

If you're considering weight loss options, know that sleeve gastrectomy leads to about 2.5 times more weight loss than semaglutide in the first year.

This was a non-randomized study with only 71 people, so results may not apply to everyone. Surgery is irreversible and carries surgical risks.

medium confidence

If using semaglutide, plan for long-term use or have a strategy to maintain weight loss after stopping, because regain is common (32% regained to baseline or higher).

The study only followed people for 12 months. Longer-term data on weight maintenance after drug discontinuation is needed.

medium confidence

Monitor lipid profiles: surgery improved triglycerides and 'good' cholesterol more than the drug, which may offer extra cardiometabolic benefits.

Baseline differences in triglycerides and HbA1c between groups could have affected results. The study didn't measure long-term cardiovascular outcomes.

low confidence

Why this study matters

Surgery vs. drug: The weight loss gap is huge

At 12 months, sleeve gastrectomy patients lost 28.6% of their total body weight, while semaglutide patients lost only 11.3% (p < 0.001). In absolute terms, surgery patients dropped from 89.9 kg to 64.6 kg, whereas drug patients went from 90.1 kg to 80.9 kg.

This shows that for people with obesity (BMI 30-35), a one-time surgery provides about 2.5 times more weight loss than a daily/weekly injection, at least in the first year.

Weight regain after stopping semaglutide is common

Among the 25 patients who stopped semaglutide after 6 months, 32% regained all the weight they lost (or more) by 12 months. The average weight went from 74.6 kg at 6 months back up to 83.2 kg at 12 months.

This highlights that obesity is a chronic disease: the drug works only while you take it. Many people think they can stop after reaching a goal, but the weight often returns.

Surgery improves 'good' cholesterol and triglycerides more

Sleeve gastrectomy led to significantly greater reductions in triglycerides (Δ0.94 vs 0.40 mmol/L, p=0.005) and increases in HDL-C (Δ+0.32 vs +0.05 mmol/L, p<0.001) compared to semaglutide at 6 months.

These improvements in blood fats are linked to lower heart disease risk. Surgery not only helps weight but may offer additional heart benefits beyond the drug.

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Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.