Background: Epidemiological evidence suggests that timing of introduction of solid foods may be associated with subsequent obesity, and the association may vary by whether an infant is breastfed or formula-fed.
Methods: We included 1181 infants who participated in the Infant Feeding Practices Study II (IFPS II) and the Year 6 Follow Up (Y6FU) study. Data from IFPS II were used to calculate the primary exposure and timing of solid food introduction (<4, 4-<6, and ≥6 months), and data from Y6FU were used to calculate the primary outcome and obesity at 6 years of age (BMI ≥95th percentile). We used multivariable logistic regression to assess the association between timing of the introduction of solids and obesity at 6 years and test whether this association was modified by breastfeeding duration (breastfed for 4 months vs. not).
Results: Prevalence of obesity in our sample was 12.0%. The odds of obesity was higher among infants introduced to solids <4 months compared to those introduced at 4-<6 months (odds ratio [OR] = 1.66; 95% CI, 1.15, 2.40) in unadjusted analysis; however, this relationship was no longer significant after adjustment for covariates (OR = 1.18; 95% CI, 0.79, 1.77). Introduction of solids ≥6 months was not associated with obesity. We found no interaction between breastfeeding duration and early solid food introduction and subsequent obesity.
Conclusions: Timing of introduction of solid foods was not associated with child obesity at 6 years in this sample. Given the inconsistency in findings with other studies, further studies in larger populations may be needed.