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O0021 VALIDITY OF BMI AS A MEASURE OF OBESITY IN AUSTRALIAN CAUCASIAN AND AUSTRALIAN SRI LANKAN CHILDREN

Wickramasinghe, V. P.1; Cleghorn, G.1; Abbott, R. A.2; Murphy, A.1; Edmiston, K. A.1; Davies, P. S. W.1

Journal of Pediatric Gastroenterology and Nutrition: June 2004 - Volume 39 - Issue - p S15
ABSTRACTS: Oral Presentation Abstracts
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1Children’s Nutrition Research Centre, Department of Paediatrics and Child Health,2School of Human Movement Studies, University of Queensland, Brisbane, Australia

Submitted by: PWickramasinghe@ccs.uq.edu.au

Introduction: Overweight and obesity are associated with cardiovascular and other risk factors1. This study is focused on determining the ability of present IOTF and CDC/NCHS, BMI based cut-off values in diagnosing obesity among Australian children of Caucasian and Sri Lankan origin.

Methods: The study was conducted at The University of Queensland and involved 5.00–14.99 year old children. All Caucasian and 60% of Sri Lankans were born in Australia and remainder had been living for more than 3 yrs (6.8±2.4 yrs). Total body water was determined by deuterium dilution and fat free mass and hence FM derived using age and gender specific constants2. A %FM of 30% for girls and 20% for boys was considered as cut-off level for obesity1.

Results: 96 Caucasians (M/F:44/52) and 42 Sri Lankans (M/F:27/15)were studied. FM and BMI were closely related in both Caucasians (r=0.81, p<0.001) and Sri Lankans (r=0.92, p<0.001). Percentage FM and BMI also had a significant association; Caucasians (r=0.42, p<0.001) and Sri Lankans (r=0.68, p<0.001). Obesity cut-offs recommended by IOTF failed to detect a single case of obesity. CDC/NCHS cut-offs detected cases of obesity with a low sensitivity (table I). Both IOTF and CDC/NCHS cut-offs had a specificity of 100% and the efficiency varied between 34% to 70%.

Table 1

Table 1

Conclusion: Diagnostic tests detecting obesity should be able to estimate the %FM with greater accuracy, as it is the factor that is associated with morbidity. BMI is a poor indicator of the %FM and the commonly used cut-offs were not sensitive enough to detect cases of childhood obesity in this study. In order to improve the diagnosis of obesity either BMI cut-off values should be revised to increase the sensitivity or, the possibility of using other indirect methods of estimating the %FM should be explored.

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Reference(S):

Dwyer T, Blizzard CL. Defining obesity in children by biological endpoint rather than population distribution. Int. J Obesity. 1996;20:472–480.
Lohman TG. Assessment of body composition in children. Ped. Ex Sci. 1989;1:19–30.
© 2004 Lippincott Williams & Wilkins, Inc.