Appropriate Cutoff Points for Body Mass Index and Waist-To-Hip Ratio for a Large Sample of Adult in Bandar Abbas, Iran

Two popular indicators for detecting obesity are body mass index (BMI) and waist-to-hip ratio (WHR).
The primary purpose of this study was to examine the agreement between the BMI and WHR classifications in diagnosing obesity among adult Iranians by using cutoff points of world health organization (WHO) gold standards. The secondary purpose was to estimate suitable cutoff points for BMI and WHR for various sex and age-groups.
The study was cross-sectional. The data were obtained from 13,691 females and 5,675 males between 2009 and 2014. Body composition indices were measured by bioelectrical impedance method (BIA). Percentage of body fat (PBF), total fat (TF), BMI, and WHR were determined. Data analysis included t-test, chi-square test, receiver-operating characteristic (ROC) curves, Fisher’s r-to-z transformation, linear regression, and Hanely formula.
In the WHR classification, nearly 78% of obese subjects had been wrongly classified as non-obese, but only 15.8% of obese females were wrongly classified as non-obese. The WHR was ineffective in detecting obesity among males between 20 and 39 years old. By the BMI classification, 42.5% of obese males had been wrongly classified as non-obese, but it was effective in detecting obesity in females between the ages of 20 and 39 years.
The suitable BMI cutoff points for detecting obesity for adult Iranians are 27.7 in all subjects, 27.7 in females, and 27.3 in males, which are all less than the BMI of 30 recommended by the WHO. On the basis of the WHR, they are 0.88 and 0.83 for males and females, respectively, which are less than the recommended cutoff points for Europeans but similar to those Eastern Asians.