Objective: To assess the relationship between size and growth measurements in infancy to body mass index (BMI) at 6 y.
Design: A longitudinal observation study on randomly chosen infants' growth and consumption in infancy. Follow-up until the age of 6 y.
Subjects: A total of 90 children who were born healthy and full-term.
Measurements: Weight and height were measured at maternity wards and healthcare centers in Iceland throughout infancy and at 6 y. Food records were made every month during infancy. At 2, 4, 6, 9 and 12 months, food was weighed to calculate food and nutrient intake.
Results: Weight gain from birth to 12 months as a ratio of birth weight was positively related to BMI at the age of 6 y in both genders (B=2.9+/-1.0, P=0.008, and B=2.0+/-0.9, P=0.032 for boys and girls, respectively). Boys in the highest quartile of protein intake (E%) at the age of 9-12 months had significantly higher BMI (17.8+/-2.4 kg/m(2)) at 6 y than the lowest (15.6+/-1.0 kg/m(2), P=0.039) and the second lowest (15.3+/-0.8 kg/m(2), P=0.01) quartile. Energy intake was not different between groups. Together, weight gain at 0-12 months and protein intake at 9-12 months explained 50% of the variance in BMI among 6-y-old boys.
Conclusion: Rapid growth during the first year of life is associated with increased BMI at the age of 6 y in both genders. In boys, high intake of protein in infancy could also contribute to childhood obesity.