BMI, waist-circumference and waist-hip-ratio as diagnostic tests for fatness in adolescents

Abstract

OBJECTIVE:To evaluate the diagnostic accuracy of body mass index (BMI, kg/m 2 ), waist-circumference (WC) and waist-hipratio (WHR) as diagnostic tests for detecting fatness in adolescents. DESIGN: A cross-sectional analysis of 474 healthy adolescents aged 17 y was used. Measurements of height, weight, WC, hipcircumference and body fat percentage (%BF) were obtained. The diagnostic accuracy for detecting excess fatness was evaluated through receiver operating characteristics (ROC) analyses with %BF, measured by densitometry (air-displacement plethysmography), as reference test. RESULTS: BMI and WC showed strong positive correlation (r ¼ 0.68-0.73; Po0.0001) with %BF in both sexes, but the correlation was weaker for WHR (r ¼ 0.30-0.41; Po0.0001). For overweight and obesity in boys and obesity in girls, the area under the ROC curve was high (0.96-0.99) for BMI and WC. WHR was not significantly better than chance as diagnostic test for obesity in girls. For BMI and WC, highly sensitive and specific cutoffs for obesity could be derived, while larger trade-offs were needed for detecting overweight in girls. The cutoffs producing equal sensitivity and specificity were lower than the ones minimizing the absolute number of misclassifications. The latter approached internationally recommended reference values, but were still several units lower for BMI in girls and several centimeters lower for WC in boys. CONCLUSION: BMI and WC were found to perform well as diagnostic tests for fatness, while WHR was less useful. The discrepancies between cutoffs producing equal sensitivity and specificity, cutoffs minimizing the absolute number of misclassifications and internationally recommended reference values for overweight and obesity highlight the importance of specifying the characteristics of classification systems for different settings.

Waist circumference and body mass index in Chinese children: cutoff values for predicting cardiovascular risk factors

“…38 WC showed a slightly stronger association than BMI with the lipid and insulin risk factors, supporting the growing use of WC in preference to BMI 39,40 and consistent with the fact that WC is a measure of central obesity which is specifically related to the presence of CV risk factors. 41,42 Weight/hip ratio and weight/height ratios, as previously used in adults 43,44 albeit controversially in children, 15,21,45,46 were shown to be less strongly associated with the CV risk factors.…”

Evaluation of BMI-based classification of adolescent overweight and obesity: choice of percentage body fat cutoffs exerts a large influence. The COMPASS study

“…Some studies have evaluated their diagnostic accuracy for adiposity, but as no accepted standard exists for classification of overweight and obesity based on body fat percentage (%BF), different cutoffs have been used (Reilly et al, 2000;Neovius et al, 2004Neovius et al, , 2005Zimmermann et al, 2004).…”

“…In a sample of 5-to 18-year-old subjects they found that 25%BF for boys and 30%BF for girls, respectively, were suitable to define excess fatness. These cutoffs have been used in evaluations of BMI-based classification of overweight (Sardinha et al, 1999;Neovius et al, 2004Neovius et al, , 2005.…”

Developing waist-to-height ratio cut-offs to define overweight and obesity in children and adolescents

“…The BMI is a proxy for body size (12) , whereas the WC measure reflects subcutaneous and visceral fat depots and can predict health risks in adults and children as young as 10 years of age (10) .…”