Timing of Infant Formula Introduction in Relation to Body Mass Index and Overweight at Ages 1 And 3 Years: the Born in Guangzhou Cohort Study (BIGCS).

Mounting evidence suggests that the first few months of life are critical for the development of obesity. The relationships between the timing of solid food introduction and the risk of childhood obesity have been examined previously, however, evidence for the association of timing of infant formula introduction remains scarce. This study aimed to examine whether the timing of infant formula introduction is associated with growth z-scores and overweight at ages 1 and 3 years. This study included 5733 full term (≥37gestational weeks) and normal birthweight (≥2500g and <4000g) children in the Born in Guangzhou Cohort Study, a prospective cohort study with data collected at 6 weeks, 6, 12, and 36 months. Compared with infant formula introduction at 0-3 months, introduction at 4-6 months was associated with the lower BMI, weight-for-age and weight-for-length z-scores at 1 and 3 years old. Also, introduction at 4-6 months was associated with the lower odds of at-risk of overweight at age 1 (adjusted odds ratio (OR) 0.72, 95%CI 0.55, 0.94) and 3 years (adjusted OR 0.50, 95% CI 0.30, 0.85). Introduction at 4-6 months also decreased the odds of overweight at age 1 year (adjusted OR: 0.42, 95% CI: 0.21, 0.84), but not at age 3 years. Based on our findings, compared with introduction within the first 3 months, introduction at 4-6 months has a reduction on later high BMI risk and at-risk of overweight. However, these results need to be replicated in other well-designed studies before more firm recommendations can be made.