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The use of waist-to-stature ratio to identify underweight and overweight in adolescents.

OBJECTIVES
To examine the percentile distribution of waist-to-stature ratio (WSR) and derive WSR cut-offs for underweight, normal weight, and overweight based on the International Obesity Task Force (IOTF) and local weight-for-height standards in Hong Kong Chinese adolescents.


METHODS
In the Hong Kong Student Obesity Surveillance project in 2006-2007, height, weight and waist circumference of 13 568 (40.3% boys) Chinese adolescents aged 12-18 were measured. Smoothed percentile distributions of WSR by age and sex were examined using Lambda-Mu-Sigma (LMS) regression. The sex- and age-specific WSR values corresponding to underweight and overweight, as defined by the IOTF and local weight-for-height standards, were determined using receiver operating characteristic curves.


RESULTS
The percentile values of WSR were stable across age in both sexes. In general, WSR values of 0.40 and 0.46 corresponded to underweight and overweight, respectively, as defined by both IOTF and local weight-for-height standards. As a reference for normal weight status, the median weight-for-height values corresponded to a WSR value of 0.42 in most sex-age subgroups.


CONCLUSION
Sex and age independent WSR cut-off values for underweight, median weight and overweight in Hong Kong adolescents were identified. WSR is potentially a practical indicator for adolescents to monitor their weight status.