http://www.ncbi.nlm.nih.gov/pubmed/22935738

Med Sci Sports Exerc. 2012 Aug 29. [Epub ahead of print]

Prospective BMI category change associated with cardiovascular fitness change.

Baranowski T, Chen TA, Mendoza JA, O'Conno T, Baranowski J, Jago R.

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.