Body Mass Index Category Transitions in Childhood and Probability of Obesity at Age 13

Understanding how children move between Body Mass Index (BMI) categories may improve early detection of those at risk of persistent obesity. This study explored transitions between BMI categories during childhood and their association with the probability of obesity at Age 13.

Routine BMI measurements at Ages 2, 4, 6, 8, and 13 years were obtained retrospectively from child health records. The International Obesity Task Force cut-offs were used to define overweight and obesity and to calculate BMI-for-age z-scores. Logistic regression models were used to estimate the probability of obesity at Age 13, depending on combinations of BMI categories at earlier ages (4, 6, and 8 years).

A total of 360 957 height and weight observations from 124 470 children were included. The predicted probability of obesity at Age 13 was 8%-10% among children with overweight at Ages 4, 6, or 8 years, and 38%-51% among those with obesity in earlier ages. Probabilities were stable across ages and only marginally influenced by prior transitions between BMI categories.

Early childhood obesity was strongly associated with adolescent obesity, whereas overweight was associated with a substantially lower risk of progression, even among children whose BMI had recently increased from normal weight.