Background: Childhood obesity is a recognized public health concern worldwide. It is essential to study the natural progression of obesity in the interest of prevention. This study aimed to describe the dynamic changes in weight status among elementary school children and identify the significant factors influencing the progression or regression of weight status. Methods: This study involved 928 elementary school children who were followed up annually during their elementary school years. Heights, weights, and vital capacity (VC) were measured each school year. A multistate Markov model containing three weight states was fit to longitudinal weight status data. Results: Children with healthy weight and obesity tended to stay in their preceding weight state. Children with overweight, in contrast, were more likely to move to the other two states. The mean sojourn time in obesity and in overweight states was 5.15 years (95% confidence interval [CI]: 4.22-6.3) and 2 years (95% CI: 1.76-2.28), respectively. Children in lower grades, those with a lower VC index, those with a higher initial BMI, those with a higher annual weight increment, and boys were at increased risk of progression to overweight or obesity, with a decreased probability of regression. Conclusions: Children with obesity were more resistant to recovery than those with overweight. Prevention and intervention measures should be adopted early when abnormal weight onset occurs. The multistate Markov model was an advanced tool to analyze dynamic changes in status and identify significant factors for progression and regression and helped to develop prevention and intervention targeting strategies.
Keywords: childhood obesity; longitudinal; multistate Markov model; weight gain.