Bioelectrical Impedance versus Body Mass Index for Predicting Body Composition Parameters in Sedentary Job Women

Objective: Nowadays the value of bioelectrical impedance analysis (BIA) in the estimation of body adiposity both on a clinical basis in the individual and epidemiologically in large populations is of great interest. The current study determine accuracy of BIA compared with body mass index (BMI) measurement for estimating body composition in a group of normal weight employee women with a sedentary job status. Materials and Methods: Forty normal weight women employed in a private institute in Tehran, Iran, participated in this study. Body composition parameters including percentage body fat, percentage visceral fat, and percentage muscular mass were measured by BIA and BMI was calculated. Results: There were strong direct correlations between one-year BMI value changes and changes in two body composition indices of percentage body fat, and percentage visceral fat, as well as an adverse correlation with the changes in percentage muscular mass. Similar association was only observed between change in basal metabolic rate (BMR) value measured via BIA and percentage body fat, neither percentage visceral fat nor percentage muscular mass. The observed correlation between percentage body fat and BMR was considerably weaker than the relationship between this composition index and BMI value. According to the ROC curve analyses, both BMR and BMI parameters had acceptable values for discriminating decreased from increased percentage body fat; however, the discriminative power of BMR value (c=0.762) was lower compared with BMI measurement (c=0.887). As we considered BMI as a gold standard value, BIA yielded a sensitivity of 70.0% and a specificity of 70.0% for determining changes in percentage body fat. Conclusion: BIA technique is not superior to BMI measure as a predictor of body composition parameters.