Previous studies have suggested that that the timing of solid food introduction in infants may be associated with childhood obesity. This study set out to examine the association between timing of introduction of solid foods during infancy and obesity at 3 years of age.

This research studied 847 children in Project Viva, a prospective pre-birth cohort study. The primary outcome was obesity at 3 years of age (BMI for age and gender 95th percentile). The primary exposure was the timing of introduction of solid foods, categorized as <4, 4 to 5, and 6 months. Separate logistic regression models for infants who were breastfed for at least 4 months ("breastfed") and infants who were never breastfed or stopped breastfeeding before the age of four months ("formula-fed"), adjusting for child and maternal characteristics, which included change in weight-for-age z score from 0 to 4 months–a marker of early infant growth.

In the first 4 months of life, 568 infants (67%) were breastfed and 279 (32%) were formula-fed, and by the age of 3 years, 75 children (9%) were obese. Among breastfed infants, the timing of solid food introduction was not associated with obesity (odds ratio: 1.1 [95% confidence interval: 0.3–4.4]). Among formula-fed infants, introduction of solid foods before 4 months was associated with a sixfold increase in obesity at age 3 year and the association was not explained by rapid early growth (odds ratio after adjustment: 6.3 [95% confidence interval: 2.3–6.9]).

Among formula-fed infants or infants weaned from breastmilk before the age of 4 months, introduction of solid foods before the age of 4 months was associated with increased odds of obesity at age 3 years.

Susanna Y. Huh, Sheryl L. Rifas-Shiman, Elsie M. Taveras, MD, Emily Oken, Matthew W. Gillman, (2011) Timing of Solid Food Introduction and the Risk of Obesity in Preschool-Aged Children, Pediatrics, Feb 2011, DOI:10.1542/peds.2010-0740