The Healthy Fitness Zone Continuum Score as a Measure of Change in Body Mass Index of School-Aged Children and Adolescents, Georgia, 2012-2014

Objectives: The FitnessGram Healthy Fitness Zone continuum (HFZc) score reflects the relative difference of a person's body mass index (BMI) from the established FitnessGram standard. As such, it may provide added utility for public health programming and research on obesity among school-aged children and adolescents. We used the standard BMI Z (BMIz) score and the alternative HFZc score to describe changes in BMI of school-aged children and adolescents in Georgia over time. Methods: We compiled 2012-2014 BMI data from the Georgia FitnessGram database. The sample included 162992 boys and 141711 girls enrolled in 239 schools from a large urban district in Georgia. We analyzed trends in BMIz and HFZc scores separately for normal-weight, overweight, and obese categories for school-aged children and adolescents using hierarchical linear models. Results: From 2012 to 2014, the BMIz score shifted favorably in up to 40.7% (2052/5047) of normal-weight, 51.0% (758/1485) of overweight, and 52.8% (5430/10279) of obese students. We also found favorable shifts in HFZc score in up to 69.8% (105831/151739) of normal-weight, 78.3% (3605/4603) of overweight, and 80.8% (8305/10279) of obese students. Conclusions: Compared with the BMIz score, the HFZc score may be a better indicator of favorable changes in BMI over time among school-aged children and adolescents with different baseline BMI levels, making it potentially valuable for use in individualized assessments, school programs, obesity research, and public health curriculum and policy development.