Association Between Waist-to-Height Ratio And Fitnessgram® BMI Classification In Sixth-grade Children

Abstract

FITNESSGRAM has established criterion standards for body composition and body mass index (BMI) according to gender and age in children. Standards for aerobic capacity (AC) have also been established to assess cardiorespiratory function. Waist-to-Height ratio (WHtR) has been shown to be a strong indicator of metabolic syndrome in youth. PURPOSE: The purpose of this study was to determine the association between WHtR and FITNESSGRAM BMI classification in sixth-grade children. METHODS: Subjects were 528 sixth-grade boys and girls, ages 11-13, who completed each of the FITNESSGRAM components as a part of their yearly assessment. In addition to height and weight, subjects were also measured for waist circumference. AC was determined from one-mile run/walk times, age, gender and BMI. The percent of these students classified within the Healthy Fitness Zone (HFZ) were 46% for BMI, and 52% for AC. The percent of these students classified as High Risk were 43% for BMI, and 31% for AC. RESULTS: The correlation between WHtR and BMI was .92, and the correlation between BMI and AC was -.75. The correlation between WHtR and AC was -.70. Receiver Operating Characteristic (ROC) analysis indicated that a WHtR of 0.451 represents the best cut-off score for classifying girls within the HFZ for BMI, with 91% classified correctly, and AUC = .96. Also, a WHtR of 0.475 represents the best cut-off score for classifying boys within the HFZ for BMI, with 90% classified correctly, and AUC = .95. For determining High Risk classification for BMI, a WHtR of 0.476 represents the best cut-off score for classifying girls as High Risk for BMI, with 90% classified correctly, and AUC = .96. Also, a WHtR of 0.484 represents the best cut-off score for classifying boys as High Risk for BMI, with 94% classified correctly, and AUC = .97. CONCLUSIONS: WHtR is strongly associated with classification according to FITNESSGRAM BMI standards in sixth-grade children. These data suggest that a WHtR of .451 for girls and .475 for boys are the best criteria for HFZ classification for FITNESSGRAM BMI. Also, a WHtR of .476 for girls and .484 for boys are the best criteria for High Risk classification for FITNESSGRAM BMI. Reduction of WHtR may provide important benefits since children in the High Risk category are most likely to develop problems related to metabolic syndrome as adults.