Abstract

Background: Obesity is defined as an excess of body fat that is sufficient to affect adversely on health. The Body Fat Percentage (BFP) of a human or other living being is the total mass of fat divided by total body mass. Bioelectrical impedance analysis has been shown to be more precise for determining lean or fat mass in humans, In comparison with body mass index, anthropometric and skin fold methods, Bioelectrical Impedance Analysis (BIA) is commonly used method for estimating body composition, and in particular Percentage of body fat . BIA is known to provide a rapid, non-invasive and relatively accurate measurement of body composition
Aim: To evaluate the accuracy of body mass index in diagnosing overweight and obesity compared to percentage of body fat measured by bioelectrical impedance.
Subjects and methods: Cross sectional study for adult population age of them range from (18-65) years of both gender selected by using systematic sampling technique from private clinic during the period (1st of March to the 1st November) 2017. For each person measured the height with a regularly calibrated Stadiometer. And according to weight was recorded by bioelectrical impedance machine then enter manually age, gender and height to bioelectrical impedance technique (in body 370 machine) that is used for estimating body composition. The data will be coded and entered into Statistical Package for Social Sciences (SPSS) version 20.
Result: A total of 711 subjects had been included in this study, the male: female ratio was 0.35: 1, the mean age of subjects was 31.4 ± 10.58 range (18-65) years there was shows high validity of BMI in detecting excess of body fat as compared to Body Fat percent as a reference test. The sensitivity was 94% and specificity was 96%. For both gender. Also There was a strong and significant positive correlation between percentage of body fat and Body Mass Index and mineral density and Body Fat Mass when p<0.001 in males and females. A positive correlation also was detected between percentage of body fat and age in both genders with waist hip ratio.
Conclusion: There is high validity of body mass index in diagnosing overweight and obesity but still there are false positive and false negative cases that should be encountered.

Keywords: Obesity; Body mass index; Bio-electrical impedance