Infant BMI peak, breastfeeding, and body composition at age 3 y.

BACKGROUND With the increasing focus on obesity, growth patterns in infancy and early childhood have gained much attention. Although the adiposity rebound has been in focus because of a shown association with adult obesity, not much has been published about the infant peak in body mass index (BMI). OBJECTIVE This study links age and BMI at infant peak to duration of breastfeeding and body composition at 3 y of age. DESIGN Frequent weight and height measurements for 311 Danish children in the SKOT (Complementary and Young Child Feeding - Impact on Short and Long Term Development and Health; in Danish) cohort were used to estimate BMI growth curves for the age span from 14 d to 19 mo by using a nonlinear mixed-effects model. BMI growth velocity before peak and age and BMI at peak were derived from the subject-specific models. Information about pregnancy and breastfeeding was assessed from background questionnaires. Assessment of body composition at age 3 y was made based on bioelectrical impedance, weight, and height. RESULTS A longer duration of exclusive breastfeeding was associated with an earlier peak in infant BMI (P = 0.0003) and a lower prepeak velocity (P < 0.0001). BMI level at peak and prepeak velocity was positively associated with fat and fat-free mass at age 3 y (all P < 0.0001), whereas a later age at peak was associated with a lower fat mass, fat mass index, and fat-free mass index at age 3 y (all P < 0.001). CONCLUSIONS BMI peak characteristics are strongly associated with both duration of exclusive breastfeeding and body composition at 3 y of age. Thus, a better knowledge of characteristics and determinants of the early BMI peak is likely to improve our understanding of early development of obesity.