Adolescent growth in overweight and non-overweight children in Japan: a multilevel analysis

Background: A trend towards earlier pubertal growth has been identified along with an increase in childhood obesity rates. The study aimed to identify the differences in growth patterns during adolescence between overweight/obese and non-overweight children in Japan.

Methods: The participants were children from a prospective cohort study called Project Koshu, who were born between 1991 and 1998, in Japan. They were classified as overweight/obese or non-overweight according to their body mass index (BMI) in the first grade of elementary school (6-7 years of age) and were followed until graduation from junior high school (14-15 years of age). Anthropometric data were collected at an annual medical check-up in their school. Height gain trajectories were constructed by BMI categories using multilevel analyses. This analysis was stratified by gender.

Results: Overall, 111/850 (13.1%) girls and 109/911(12%) boys were defined as overweight/obese at baseline. Approximately 80% of the children were followed until the third grades of junior high school. Overweight/obese girls gained more height in the first half period, reached their peak height gain about a year earlier than non-overweight girls, and experienced an earlier decline in height gain. Similarly, overweight/obese boys gained more height than non-overweight boys initially. Additionally, non-overweight boys maintained a higher rate of height gain from the age at peak height gain, although the age at peak height gain did not differ between the two groups.

Conclusions: The overweight/obese children grew faster than the non-overweight children in the early pubertal stages, and the non-overweight children caught up and exceeded in height gain at a later stage.