Early‑Life Antibiotics May Boost Obesity Risk
Why cautious prescribing in the first 24 months could shape a child’s long‑term weight trajectory
Topline
A Finnish cohort study of 33 095 children found that antibiotic exposure during the first two years of life was linked to a modest but measurable rise in BMI at age 2 and a 20 % higher risk of obesity by age 12, underscoring the need for judicious use of antibiotics in toddlers.
Study Details
At the 2025 Pediatric Academic Societies (PAS) Meeting, researchers from the University of Oulu presented findings from a cohort of over 33,000 Finnish children born via vaginal delivery. The study aimed to explore whether antibiotic exposure at different early life stages affects long-term obesity risk.
Researchers assessed four key exposure periods:
One year before pregnancy
During pregnancy
Perinatal period (around birth)
The child’s first two years of life
Antibiotic use during the first two years of life stood out as the only period significantly linked to future obesity.
Methodology
This was a retrospective, register-based cohort study using national health records. Researchers tracked BMI-for-age z-scores at age 2 and monitored overweight and obesity rates up to age 12. Regression models controlled for maternal BMI, smoking, birthweight, gestational age, and socioeconomic status.
Key Findings
Children exposed to antibiotics in their first two years had:
A 0.067-point increase in BMI-for-age z-score at age 2
A 9% higher chance of being overweight by age 12
A 20% higher risk of obesity by age 12
No significant associations were found for antibiotic exposure during pregnancy, before pregnancy, or the perinatal period after adjusting for confounding factors.
Lead researcher noted the findings were surprising, especially given past studies that emphasized the role of perinatal exposure on gut microbiota changes.
Implications for Practice
For Parents and Caregivers
Ask your healthcare provider whether antibiotics are truly necessary for minor infections.
Consider the potential long-term impacts on your child’s metabolism.
Support healthy gut flora with a fiber-rich, balanced diet when antibiotics are needed.
For Pediatricians and Providers
Strengthen antibiotic stewardship in clinical settings, especially during early childhood.
Educate families on alternatives to antibiotics when appropriate.
Monitor growth more closely in children who’ve received repeated antibiotics early in life.
Although this study doesn't establish causality, it adds to growing evidence that antibiotic use in infancy should be limited to situations where it is clearly warranted.