Early introduction of solid foods raises obesity risk in formula-fed infants

Investigators examined the extent to which introduction of solid foods to infants younger than 4 months is associated with an increased risk of obesity at 3 years. The study group consisted of 847 children in a prospective birth cohort study who were divided into 2 groups: those who were at least partly breastfed for at least 4 months (67%) and those who were formula fed (32%), defined as children who were never breastfed or stopped breastfeeding before the age of 4 months.

Six months after delivery, each mother completed a questionnaire about when she introduced each of 10 solid foods or food groups. When the children were 3 years old, investigators checked their height and weight, calculated the sum of subscapular and triceps skinfold thicknesses, and calculated age- and gender-specific body mass index (BMI) percentiles and z scores. They defined obesity as a BMI in the 95th percentile or higher for age and gender.

Not only were mothers of formula-fed infants more likely than mothers of breastfed infants to introduce solid foods before their infants reached 4 months of age (33% vs 8%), but among formula-fed infants introduction of solid foods before 4 months was associated with a 6-fold increase in the odds of obesity at 3 years of age.

Commentary

It is thought that breastfed babies compensate for additional calories from solid foods by reducing their intake of breast milk, either through self-regulation or their mothers' increased awareness of satiety cues. The same is not seen in bottle-fed infants. This may explain the difference seen here. This study supports American Academy of Pediatrics recommendations for avoiding solid foods until babies are at least 4 months of age. -Michael Burke, MD