Med Sci Sports Exerc. 2012 Aug 29. [Epub ahead of print]
Prospective BMI category change associated with cardiovascular fitness change.
Source
1Baylor College of Medicine, Children's Nutrition Research Center, Houston, TX 2University of Bristol, Centre for Exercise, Nutrition & Health Sciences, Bristol, UK.
Abstract
PURPOSE:
Test the relationship of change in body mass index (BMI) percentile score group (from 6 to 8 grade) with change in cardiovascular fitness (CVF), baseline BMIz-score and CVF.
METHOD:
3,998 (92%) children in the HEALTHY trial provided complete data at the beginning of 6 and end of 8 grades. Height and weight were assessed according to standardized protocol. CVF was measured using the 20 meter shuttle run. Changes in BMI percentile were categorized into five groups: increased a BMI category, stayed obese, stayed overweight, stayed healthy weight, and decreased a BMI category. Data were analyzed separately by gender, controlling for race, parental education, change in pubertal stage, and baseline BMIz-score and CVF.
RESULTS:
Youth (males and females) who lowered their BMI group or remained in the healthy or overweight groups had significantly larger increases in CVF, than the stayed obese or increased a BMI category groups. But these relationships accounted for a small percentage of variance (i.e. weak relationship). Staying obese was associated with the highest baseline BMIz-score, with the second highest among those who decreased a BMI category. BMI category change accounted for the most variance in baseline BMIz-score.
CONCLUSIONS:
Changes in BMI categories were substantially more strongly related to 6 grade values of BMIz-score than to CVF changes. Since pre-existing adiposity may inhibit adiposity change, changes in CVF and adiposity should be attempted prior to middle school.
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