Cardiorespiratory fitness status and body mass index change over time: A 2-year longitudinal study in elementary school children

Objective. This study aimed to examine the prospective relationship of baseline body mass index (BMI) and performance in a cardiorespiratory fitness (CRF) field test with a change in BMI (Delta BMI) over a 2-year period in a sample of rural children from elementary school in Fundao, Portugal. Methods. Obesity status was obtained by the age- and sex-specific BMI cut-off points and CRF by a 9-minute run test. Results. BMI stratification at baseline showed that overweight/obese children were over 11 times (OR = 11.31; p = 0.007) more likely to be Delta BMI gainers than their normal weight peers. Those who were classified as unfit were 3.9 times more likely to be Delta BMI gainers than those classified as fit at baseline. Both BMI at time 1 and CRF change (Delta CRF) were not significantly associated with A BMI over time. Conclusion. The findings of this study suggest that children who have higher BMI and lower CRF are likely to have greater BMI gain over time.