Longer Breastfeeding Is Associated With Healthier Body Mass Index Trajectories and Lower Risk of Overweight and Obesity in Youth Aged 9–12 Years
Authors' conclusion
Amongst initially healthy weight youth, breastfeeding, especially beyond 6 months, was associated with healthier BMI trajectories and lower unhealthy weight risk in boys. Although these sex-specific patterns warrant further research, our findings suggest that the associations between breastfeeding and body weight development extend into adolescence.
Study context
- Population
- Youth aged 9–12 years, all healthy weight at baseline, Adolescent Brain Cognitive Development (ABCD) Study; 50.7% female; 52% breastfed more than 6 months10,586 observations
- Participants
- 4,161 participants
- Exposure
- Breastfed vs not breastfed
- Outcome
- BMI trajectories (kg/m²) and risk of unhealthy weight (BMI ≥ 85th percentile)
- Follow-up
- Ages 9 to 12; unhealthy weight by ages 11-12
Methodological detailslinear mixed-effects models, analyses stratified by sex
- Linear mixed-effects models
- Analyses stratified by sex
Main finding
As reported in the abstract
- Breastfeeding × age interaction: lower BMI trajectories in breastfed youth
- β = −0.005, p < 0.001
- Breastfeeding × age, breastfed >6 months
- β = −0.006, p < 0.001
- Breastfeeding × puberty: lower BMI trajectories across pubertal stages, boys only
- β = −0.06, p = 0.017
- Breastfeeding × puberty, boys breastfed >6 months
- β = −0.11, p = 0.005
- Unhealthy weight risk at ages 11-12 with breastfeeding, boys only
- RR = 0.78, p = 0.002
- Unhealthy weight risk, boys breastfed >6 months
- RR = 0.52, p < 0.001
Observational data: associations, not effects.
Original publication
Longer Breastfeeding Is Associated With Healthier Body Mass Index Trajectories and Lower Risk of Overweight and Obesity in Youth Aged 9–12 Years. Pediatr Obes. Published 7 January 2026. doi:10.
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