Cohort studyindependent cross-checkabstract checked★ key study I-ABX-112 standard review
Twin study finds no link between baby antibiotics and overweight
Early-life antibiotic use and children with overweight and obesity: a Dutch twin cohort study.
Overview
Feil RS et al.. Int J Obes (Lond) 2026 · PMID 42457938 · DOI 10.1038/s41366-026-02164-6
Among 34,142 Dutch twins, early antibiotics were not linked to overweight or obesity.
Does the study support the specific claim? No · Methodological quality: moderate
Plain-language summary
Study explained simply
- What did the researchers want to find out?
Test the antibiotic-weight link while controlling for family
- How was the study done?
Twin cohort
- How many people, animals or samples were studied?
34,142 twins
- What was actually found?
No association
- How large was the observed effect?
OR 1.00 (0.90-1.12)
- What do the results mean in everyday life?
Earlier links may reflect family factors
- What are the study's limitations?
Antibiotic use reported by parents
- What does it say about Elawady's specific claim?
Contradicts the claim
- Do the results apply to Germany and Europe?
High
- What can explicitly not be concluded from this study?
Effects of many courses
Scientific in-depth review
1. Full reference
- Authors
- Feil RS et al.
- Journal
- Int J Obes (Lond)
- Year
- 2026
- Identifier
- PMID 42457938 DOI 10.1038/s41366-026-02164-6
- Verification
- verified – PubMed efetch 2026-10-26 + Crossref
- Retracted
- no
- Corrections
- none
- Extent checked
- abstract only
- Conflicts of interest and funding
Authors' disclosures: one author with advisory fees from GSK, Boehringer Ingelheim and AstraZeneca (record).
2. Research question
Is early-life antibiotic use associated with childhood overweight/obesity after controlling for shared familial factors?
3. Study design and population
- Study design
- Cohort study – Retrospective twin cohort with co-twin control analysis
- Population
Twins aged 4.5-15.4 years in the Netherlands Twin Register
- Country
Netherlands
- Period
Not stated in abstract
- Sample size
34,142 twins
- Inclusion and exclusion criteria
Twin register participants with exposure and BMI data
4. Methods and endpoints
- Exposure / intervention
Any antibiotic use before age 2 (24.6%)
- Comparator
No antibiotic use; co-twin
- Endpoints
Obesity, overweight/obesity, BMI z-score
- Statistical methods
Adjusted logistic regression; matched co-twin analyses
5. Actual results
- Results
No association with obesity (OR 0.82, 95% CI 0.60-1.14) or overweight/obesity (OR 1.00, 0.90-1.12); matched co-twin analyses similar null; BMI z-scores did not differ.
- Absolute risks
1.06% obesity, 9.23% overweight/obesity overall
- Authors' conclusion
Early-life antibiotic use is not associated with an increased risk of overweight or obesity in childhood.
6. Strengths
- Large twin design controls shared genes and environment
- Recent
7. Weaknesses
- Parent-reported antibiotic use (retrospective)
- Low obesity prevalence limits power for obesity
8. Risk of bias
- Orienting tool
- ROBINS-E
- Type of assessment
- simplified assessment (abstract only)
- Full formal assessment
- no
- Overall risk of bias
- some concerns
- Rationale
Recall misclassification would bias toward null.
9. Assessment of the statistical interpretation
Null with reasonably narrow CI for overweight/obesity (0.90-1.12).
10. Relevance to the specific claim
Within-family design finds no association.
11. Independent contrary findings
Exposure by questionnaire.
12. Transferability to Germany and Europe
High (European).
13. Overall methodological judgement
Strong contradicting evidence against a causal effect on childhood weight.
| Multidimensional assessment | |
|---|---|
| Authenticity of the source | verified |
| Methodological quality | moderate |
| Risk of bias | some concerns |
| Precision of results | moderate |
| Directness | direct |
| Reproducibility | partly replicated |
| Consistency with the overall evidence | mixed |
| Regional transferability | high |
| Adequacy of the interpretation (by the archive) | not applicable |
14. Open questions
Replication with prescription records.
15. Linked fact checks
- Antibiotics make people (especially children) gain weight by altering gut bacteria, as they do in fattened poultry; early-childhood antibiotic courses raise obesity risk. – Studies contradicting or limiting the claim