Associations between Bottle-Feeding during Infancy and Obesity at Age 6 Years Are Mediated by Greater Infancy Weight
Alison K Ventura1, Ruowei Li2, Xinling Xu3
1California Polytechnic State University, Department of Kinesiology and Public Health, Center for Health Research, San Luis Obispo, CA, USA.
Insights
Increased bottle-feeding in early infancy is linked to childhood obesity at age 6. This association is significantly mediated by changes in weight-for-age z-score (ΔWAZ) during infancy, highlighting a critical developmental window.
Area of Science:
- Pediatrics
- Nutritional Science
- Public Health
Background:
- Childhood obesity is a growing public health concern.
- Bottle-feeding practices are common in infancy and may influence long-term weight trajectories.
- Understanding the mechanisms linking infant feeding to later obesity is crucial for prevention.
Purpose of the Study:
- To investigate if bottle-feeding in the first year mediates childhood obesity at age 6.
- To examine the role of change in weight-for-age z-score (ΔWAZ) during infancy as a mediator.
Main Methods:
- Causal mediation analysis applied to 1062 mother-child pairs from the Infant Feeding Practices Study II and Year 6 Follow-Up.
- ΔWAZ calculated from birth to later infancy using maternal-reported child weights.
- Questionnaires collected prenatal, postpartum (first year), and at 6 years.
Main Results:
- Rapid increases in bottle-feeding frequency in the first 6 months correlated with greater ΔWAZ.
- Larger birth weight and ΔWAZ were significant predictors of obesity at age 6.
- Bottle-feeding's effect on obesity was 59% mediated by ΔWAZ.
Conclusions:
- Increased bottle use in early infancy predicts higher risk of childhood obesity.
- The mediation effect of ΔWAZ from birth to later infancy is a key pathway.
- Early infant feeding patterns, particularly bottle use, warrant attention for obesity prevention strategies.
Abstract:
To explore whether the association between bottle-feeding during the first year and childhood obesity at age 6 years is mediated by change in weight-for-age z-score (ΔWAZ) during infancy. Participants were 1062 mother-child pairs who participated in the Infant Feeding Practices Study II and Year 6 Follow-Up. Mothers completed 1 prenatal questionnaire, 10 postpartum questionnaires during the first year, and 1 follow-up questionnaire at 6 years. Child weights were reported by mothers and used to determine ΔWAZ from birth to later infancy. Causal mediation analysis was used to determine the average direct effect of bottle-feeding on obesity at age 6 years and the average causal mediation effect of bottle-feeding through ΔWAZ. Infants who experienced rapid increases in bottle-feeding frequency during the first 6 months had significantly greater ΔWAZ compared with infants who had consistently low bottle-feeding frequency until 12 months of age [β = 0.45, 95% confidence interval (CI) 0.11-0.80]. Significant predictors of obesity at age 6 years were larger birth weight [adjusted odds ratio (AOR) = 4.27, 95% CI 2.42-7.64] and larger ΔWAZ (AOR = 1.59, 95% CI 1.29-1.98). An indirect effect of bottle-feeding, mediated via ΔWAZ, accounted for 59% of the total effect of bottle-feeding on obesity at age 6 years. Rapid increases in bottle use during the first 6 months postpartum predicted greater risk for obesity at age 6 years via an indirect mediation effect of larger ΔWAZ from birth to later infancy.
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