Comparison of bioelectrical impedance analysis and body mass index methods in determining the prevalence of overweight and obesity

  Background : Obesity has an increasing trend worldwide. Application of body mass index (BMI) cutoff points to classify obesity in different populations is controversial. On the other hand, bioelectrical impedance analysis (BIA) is a safe, accurate, reliable, and inexpensive method used in some studies to screen overweight and obesity.   Objective : Comparison of bioelectrical impedance analysis and body mass index methods in determining the prevalence of overweight and obesity.   Methods: This analytical study was performed on 187 healthy women, aged 18 to 45 years (2008). Demographic and anthropometric data were collected by trained students. Body fat percentage (BF%) and body fat mass (BFM) were measured using BIA method. Two BMI cut-off points (≥25 and ≥30 kg/m2) were used as criteria to determine the overweight and obese women, respectively. Also, two BF% cut-off points (≥30 and ≥35%) were considered to define over fat and obesity. One way ANOVA and Pearson’s correlation coefficient were used for data analysis.   Findings : The mean age of women was 34.9±8.1 years. BMI, BF% and waist-to-hip ratio were: 27.7 ± 5.8 kg/m2, 35.5 ± 6.9%, and 0.77 ± 0.08, respectively. Central obesity was prevalent in 32.6% of the subjects. The prevalence of obesity determined by BMI and BIA methods was 35.8 and 57.8%, respectively. The women within normal ranges were detected in 28.9 and 23% of subjects using BMI and BIA methods, respectively (P<0.05). Almost half of the women were overweight or obese. Women with higher age had higher BMI compared to other subjects but the difference in body fat percentage was insignificant.   Conclusion: It seems that BIA and BMI methods to act differently in determining the thin, normal, and obese women. The prevalence of obesity was higher when BIA method used.