Comparison between bioelectrical impedance analysis and body mass index methods in determination of obesity prevalence in Ahvazi women.

Background: Obesity has an increasing trend worldwide. Recently, application of body mass index (BMI) cutoff points of obesity classification for all population studies has been questioned. On the other hand, bioelectrical impedance analysis (BIA) is a safe, accurate, reliable and inexpensive method for screening the overweight and obesity in such studies.

Objectives: There were three objectives followed in this research: to determine the prevalence of obesity and overweight in married women using BMI and BIA methods; to evaluate the correlation between these methods; and to compare the women's obesity degrees according to their educational levels.

Method: Six hundred and thirty-seven healthy married women 18-40 years aged, who had referred to 14 health centers of the city of Ahvaz (center of Khouzestan province, south-west of Iran) were recruited in a cross-sectional design, and their socio-economic and anthropometric questionnaires were completed by the trained students. Body fat percent (%BF) and body fat mass (BFM) were measured using BIA method. BMI>25 and >30 kg/m(2) were used as criteria for determining the overweight and obese women, respectively. %BF>35% was regarded as cutoff for defining obesity.

Results: Mean age+/-s.d. of the women was 26.9+/-5.8 years and majority of them were housewives with secondary educational level. Their BMI, %BF, waist-to-hip ratio, and mid-upper arm circumference means were: 25.9(4.7) kg/m(2), 27.6(7.3)%, 0.75(0.08) and 27.9(3.9) cm, respectively. Central obesity was prevalent in 21.2% of the subjects. Prevalence of obesity determined by BMI and BIA methods was 18.3 and 15.5% and women within normal ranges were detected in 44.7 and 46% of the subjects by these methods, respectively. However, thin (underweight) women were 2.6 and 14.6% of the subjects studied, respectively. About one half of the women were overweight or obese. BMI was statistically correlated with BFM (r=0.86; P<0.0001) and %BF (r=0.77; P<0.0001). Women with higher educational levels had lower body fat percentage and BMI than the other subjects with lower degrees (P<0.05).

Conclusion: Obesity and overweight is prevalent in about one-half of the Ahvazian married women and more than one-fifth of the subjects have central obesity. BIA and BMI methods can similarly detect the normal and obese married women but they are different in determining the underweight female subjects. Women with higher educational grades tend to have lower BMI levels.