Meta-analysisindependent cross-checkabstract checked★ key study I-BAR-143 in-depth review
Cochrane review: surgery for obesity with type 2 diabetes
Metabolic and bariatric surgery in adults with obesity and diabetes mellitus: a network meta-analysis.
Overview
Kiesswetter et al.. Cochrane Database Syst Rev 2026 · PMID 42610488 · DOI 10.1002/14651858.CD015622.pub2
Trials show more weight loss and better blood sugar after surgery, but long-term data on complete diabetes remission, serious harms and deaths are very uncertain.
Does the study support the specific claim? Partly · Methodological quality: high
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Benefits/harms of MBS in T2D
- How was the study done?
Cochrane NMA
- How many people, animals or samples were studied?
15,282
- What was actually found?
Weight and HbA1c better; remission/mortality very uncertain
- How large was the observed effect?
RYGB weight MD -17%
- What do the results mean in everyday life?
Surgery helps, but long-term certainty is limited
- What are the study's limitations?
Few RCT participants
- What does it say about Elawady's specific claim?
Partly supports erosion claim; does not show harm
- Do the results apply to Germany and Europe?
Applicable
- What can explicitly not be concluded from this study?
Precise long-term effects
Scientific in-depth review
1. Full reference
- Authors
- Kiesswetter et al.
- Journal
- Cochrane Database Syst Rev
- Year
- 2026
- Identifier
- PMID 42610488 DOI 10.1002/14651858.CD015622.pub2
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref API
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Funded by German Federal Ministry of Education and Research (BMBF 01KG2201); one author reports industry advisory/speaker roles.
2. Research question
What are medium- and long-term benefits and harms of MBS procedures compared with each other and with non-surgical treatment in adults with obesity and T2D?
3. Study design and population
- Study design
- Meta-analysis – Cochrane systematic review with network meta-analysis (RCTs and cohort studies >=3 y), GRADE
- Population
Adults with obesity and type 2 diabetes
- Country
Multinational
- Period
Search to 25 June 2024
- Sample size
18 studies (13 RCTs n=911; 5 cohorts n=14,371); 15,282 participants
- Inclusion and exclusion criteria
RCTs and cohorts with >=3 y follow-up
4. Methods and endpoints
- Exposure / intervention
RYGB, SG, OAGB, LAGB, GCP, BPD-DS
- Comparator
Lifestyle/medical treatment and each other
- Endpoints
Weight loss, waist, T2D remission, SAE, mortality, complications, HbA1c, HRQoL
- Statistical methods
Frequentist random-effects NMA; GRADE; RoB 2/ROBINS-I
5. Actual results
- Results
Long-term weight loss greater after RYGB vs LI/MT (MD -16.95%, -24.19 to -9.71); SG MD -9.40% (very uncertain). HbA1c: RYGB MD -1.44%; SG MD -1.01% (-1.94 to -0.08). Evidence very uncertain for long-term complete T2D remission, SAE and all-cause mortality (7 RCTs, n=520). RYGB may reduce total T2D complications (RaR 0.17, 0.03-0.89; very uncertain). Cohort studies judged high/critical risk of bias.
- Absolute risks
not reported in abstract
- Authors' conclusion
RYGB, OAGB and to a lesser extent SG may improve long-term weight, partial remission and HbA1c vs lifestyle/medical treatment; for complete remission, SAE, mortality and complications evidence is very uncertain.
6. Strengths
- Cochrane methods, GRADE
- Only >=3 y follow-up
7. Weaknesses
- Few RCT participants and events
- Cohorts not GRADE-rated
8. Risk of bias
- Orienting tool
- AMSTAR 2
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- low
- Rationale
High-quality review; certainty limited by primary studies.
9. Assessment of the statistical interpretation
Wide CIs; GRADE very low/low for most long-term outcomes.
10. Relevance to the specific claim
Gives the most rigorous, sceptical calibration: randomised long-term evidence on remission durability, harms and mortality is very uncertain; benefits on weight and HbA1c are more consistent.
11. Independent contrary findings
Observational cohorts (excluded from GRADE) show larger benefits.
12. Transferability to Germany and Europe
European-funded Cochrane review.
13. Overall methodological judgement
Important tempering evidence: benefits likely but magnitude uncertain in RCTs.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | high |
| Risk of bias | low |
| Precision of results | low |
| Directness | direct |
| Reproducibility | not replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Large long-term RCTs.
15. Linked fact checks
- The diabetes remission achieved by bariatric surgery erodes over time (SOS: 72% at 2 years to 30.4% at 15 years; Adams: 75% to 51%). – Studies with mixed or unclear results
- Sleeve gastrectomy (and bariatric surgery in general) is a lethal operation that kills patients / shortens life. – Studies with mixed or unclear results