Assessment of overweight and obesity in Iranian adolescents: optimal cut-off values of anthropometric indices

Abstract

Background: Various indices have been used to estimate overweight and obesity; all have limitations and strengths. The prevalence of overweight and obesity may differ by ethnicity. Objectives: This study evaluated waist circumference (WC), waist‐to‐hip ratio (WHpR), waist‐to‐height ratio (WHtR) and neck circumference (NC) as reliable alternatives to body mass index for screening for overweight and obesity, and determined their optimum cut‐off values in different ethnic groups. Methods: The study was conducted from November 2015 to February 2016 among adolescents aged 12–14 years from 5 ethnicities in the Islamic Republic of Iran: Arab, Kurdish, Sistani & Baluchi, Turkish and Turkman. Stratified multistage sampling was used to select 2 444 students. Receiver operating characteristic curves were constructed to evaluate WC, WHpR, WHtR and NC as screening indices for overweight and obesity as categorized by body mass index centiles. Results: The prevalence of overweight and obesity in the total sample were 15.3% and 9.2% respectively, with higher rates in students of Arab, Kurdish and Turkish ethnicity. The areas under curve ranged from 0.8 to 0.9 for WC, WHtR and NC. The mean optimum values with the highest sensitivity and specificity to identify overweight were: 72.3 cm (sensitivity 0.80, specificity 0.75) for WC, 0.46 (0.85, 0.70) for WHtR and 31 cm (0.76, 0.76) for NC. For obesity mean optimum values were: 77 cm (0.84, 0.81) for WC, 0.50 (0.84, 0.84) for WHtR and 31.5 cm (0.88, 0.71) for NC. Conclusion: WC, WHtR and NC may be useful tools to screen for adiposity using their optimum values for sex and ethnicity. Keywords: overweight, obesity, anthropometric indices, adolescent, ethnicity, Iran