Thigh Circumference as a Useful Predictor of Body Fat in Adolescent Girls with Anorexia Nervosa

Background/Aim: Girls with anorexia nervosa (AN) demonstrate severe depletion of body fat. The aim of this study was to determine an accurate anthropometric measurement for clinical assessment of fat depletion in girls with AN in connection with body composition measured by dual-energy X-ray absorptiometry (DXA). Methods: In 64 female AN patients aged 12.8-23.1 years (mean 16.0 +/- 1.8), body mass index (BMI), skinfold thickness (subscapular, abdominal and triceps), mid-upper arm and thigh circumference, fat mass (FM) and lean mass were determined and compared with the data of 71 controls. Results: Girls with AN had lower anthropometric traits and were fat depleted compared to controls (14.9 +/- 7.3 vs. 27.4 +/- 6.4% of FM using DXA; all p < 0.001). BMI, thigh circumference and subscapular skinfold thickness demonstrated a very similar predictive value for DXA assessment of body fat. Based on the receiver-operating characteristic curve analysis and the determination of the positive predictive value, thigh circumference appeared the most specific and sensitive anthropometric predictor of fatness discriminating between AN and healthy girls, with the AUC value reaching 0.95 (95% Cl = 0.92-0.97). Using a cutoff value of 49.6 cm, accuracy was 90.6%, sensitivity 93% and specificity 88.7%. Conclusions:Thigh circumference strongly correlates with DXA-FM and demonstrates a slight clinical advantage over BMI. This simple measurement might also serve as a useful predictor of body fatness in adolescent girls with AN and should therefore be further evaluated in independent cohort studies. Copyright (C) 2011 S. Karger AG, Basel