Innovative Assessments Help Elucidate Sustained Improvements in Fitness and Metabolic Health in Obese Children

Abstract

Objective Treatment of childhood obesity is a medical challenge and limited data are available describing successful long term interventions. This study presents a multi-disciplinary intervention that resulted in sustained physiological improvement over a one-year period. Methods The criterion outcome variables include cardiovascular fitness (CVF) measured by a population-specific treadmill test to predict maximal oxygen uptake (predicted VO2 max) and the body composition (BC) variables of fat mass, non-bone lean mass and percent body fat from whole body dual energy x-ray absorptiometry (DXA) scans. Subjects were overweight and obese children (N=79) evaluated at baseline, 6 and 12 months at a University Hospital-based pediatric fitness clinic. Results Statistically significant improvements in non-bone lean body mass (+4.24 kg ± 5.0, p<0.0001) and predicted VO2 max (+0.14L/min ± 0.10, p<0.0001) were seen at 6 months. These significant improvements were sustained over 12 months: body fat percentage (−2.28 ± 3.49, p<0.0001), lean mass (+6.0 kg ± 4.0, p<0.0001) and predicted VO2 max (+0.22 L/min ± 0.19, p<0.0001). These results were observed despite increases in weight and body mass index (BMI) at 6-months (weight: +6.6 kg ± 6.93, p<0.0001; BMI: +0.37 ± 1.21, p=0.47) and 12-months (weight: +6.3 kg ± 5.8, p<0.0001; BMI: +0.91 ± 2.06, p=0.0002). Conclusion These results reflect the sustained effect of a multidisciplinary approach, and the value of using valid and reliable assessment methods to measure sustained physiological changes in a sample of 79 overweight and obese children.

BMI z-score in obese children is a poor predictor of adiposity changes over time

“…Finally, practicality and feasibility limit the use of DXA for monitoring changes in adiposity in obese youth and thus most clinicians utilize BMI with the supposition that an elevated BMI is equivalent to excess adiposity [ 16 – 19 ]. However, BMI is not indicative of the degree of adiposity in younger children [ 4 , 5 , 20 , 21 ].…”

“…All subjects were obese boys and girls (BMI-for-age ≥ 95 percentile) ages 4 to 18 years evaluated as part of their routine clinical care at a multidisciplinary weight management program within an academic medical center. Anthropometric and body composition measurements were collected in accordance with previously published methods [ 4 , 5 , 8 – 10 ]. Study procedures were approved by the Health Sciences Human Subjects Committee at the University of Wisconsin- Madison.…”

“…However, due to ease of acquisition, the most widely used clinical outcome variable is BMI, and standardized for age and sex, as BMIz. Previous reports, including ours evaluated the strength of how well BMIz predicts adiposity in children [ 4 , 5 ]. However, whether the longitudinal change in BMIz over time predicts a true change in adiposity is unknown.…”