ABSTRACTS: Oral Presentation Abstracts
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%.
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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