Use of Waist to Height Ratio in assessment metabolic derangements among normal and overweight/obese 5-15 year old individuals

Background and objectives Although Body Mass Index (BMI) is used to assess obesity, it does not always relate to central obesity, the main metabolic risk factor. Waist to height ratio (WHtR) is a simple index of central obesity. This study assessed its usefulness in detecting metabolic derangements in 5-15 year old Sri Lankan children. Method A cross sectional descriptive study on healthy 5-15 year old children was conducted in Colombo district. Height, weight and Waist Circumference (WC) were measured. WHtR and BMI (classified by WHO cutoff >2SD) were calculated. Obesity was defined by percentage fat mass measured by Bio Electrical Impedance Assay (BIA - InBody-230 BIA machine) and validated against Sri Lanka body composition equations. After a 12-hour overnight fast, blood was drawn for Fasting Blood Glucose (FBG) and lipid profile. Standard Oral Glucose Tolerance Test (OGTT) was performed to obtain Random Blood Glucose (RBG) at 2 hours. Metabolic Derangements (MetD) were defined as; WC for age >90th centile (UK standards); FBG>100mg/dl or RBG>140 mg/dl; HDL-cholesterol 150mg/dl; and systolic or diastolic blood pressure>+2SD for age (UK standards). Metabolic Syndrome (MetS) was diagnosed by high WC plus ≥2 other MetD. ROC curves were drawn to determine the optimal WHtR value that predicts MetS as well as ≥2 MetD. Using these cutoffs, WHtR was also validated against obesity determined by % fat mass. Results A total of 920 children (547 boys) were studied: 16.6% were obese/overweight and 55.6% had normal BMI. Close to 14% had central obesity. Those with normal BMI but having central obesity had higher total cholesterol and triglyceride levels, but were not statistically significant. WHtR detected more cases with abnormal cholesterol and HDL than BMI, but detection of cases with high triglycerides was similar to BMI. WHtR to detect MetS was 0.51 (sensitivity-1.00; specificity-0.83) in boys and 0.49 (sensitivity-0.83; specificity-0.83) in girls. To detect ≥2 MetD, WHtR was 0.42 (sensitivity-0.6; specificity-0.62) in boys and 0.45(sensitivity-0.62; specificity-0.62) in girls. Conclusions WHtR is valid in detecting metabolic derangements in this group of Sri Lankan children. The cut off values (0.5) described to detect MetS in this group of children is similar to the value described in the literature. A cutoff value of 0.45 would detect at least two MetD, thus enabling early detection of obesity related metabolic morbidity.