Infants with Excessive Weight Gain while Exclusively Breastfeeding: Follow-Up at 36 Months.

Rapid weight gain in infancy is associated with an increased risk of later adiposity. Very rarely, however, exclusively breastfed infants experience excessive weight gain (EWG) during the period of exclusive breastfeeding (EBF) when breast milk is the only source of nutrition. We investigated growth and body composition at 36 months in children experiencing EWG during EBF. Ten infants with EWG during the first 6 months of EBF were followed up at 36 months. The infants had been followed from age 5 months. Examinations included anthropometry, body composition by bioimpedance, and blood samples. Body composition and plasma leptin concentrations were available for eight and five children, respectively. From 5 to 36 months, body mass index-for-age -scores (BAZ) decreased from (mean ± standard deviation) 2.33 ± 0.94 to 1.48 ± 0.57, and only one child still being overweight (BAZ >2). Fat mass and fat mass index (FMI) decreased from 18 to 36 months (4.71 ± 0.56 to 3.57 ± 0.67 kg and 6.50 ± 0.34 to 3.66 ± 0.72 kg/m, respectively) with a concurrent 45% decrease in leptin. The increase in lean mass was higher than the increase in weight (5.27 versus 3.65 kg, respectively) due to fat loss. There was substantial conformity within the sample in the patterns of body composition change. This unusual group of children continued to decrease in BAZ and FMI with a concomitant increase in fat-free mass, indicating an ongoing normalization of body weight and composition.