[Association between body mass index (BMI) and height from birth to 5 years in Chilean preschool children].

BACKGROUND: It has been shown that excess weight gain during childhood is associated with a greater risk of obesity; this relationship may be mediated by growth in height. AIM: To quantify the associations between z scores for body mass index (BMIZ) and height for age (HAZ) from birth to 5 years of age and to assess how this association varies according to age and adiposity. MATERIAL AND METHODS: Weight and height were recorded at 11 occasions from birth on a cohort of 1089 Chilean five year-old children with a birth weight > 2500 g. BMI, BMIZ, HAZ and prevalence of obesity were calculated. We determined the cross-sectional association between BMIZ and HAZ for the total sample and by 3 BMI Z categories, using Pearson correlation. We determined the probability of obesity according to four HAZ categories. RESULTS: Obesity increased continuously reaching approximately 16% at 5 years. Stunting was virtually nonexistent. No association between BMIZ and HAZ was observed at birth, while at 1 and 2 months, leaner infants had lower stature. No association between these parameters was observed between 6-24 months, while after 3 years, a clear relationship was observed. CONCLUSIONS: The probability of a preschool child of being obese is less than 10% with a HAZ is < 0. Nevertheless, children with heights above the median (even within the normal range) have an increased risk of obesity, especially after 3 y of age. Between 0-5 years, the relationship between weight and height varies by age and adiposity.