Reliability of bioelectrical impedance analyzers

Abstract

Obesity is a major contributor to many preventable morbidities and mortalities. Concurrently, there is a minimal, essential amount of fat necessary for good health. Therefore, the accurate estimation of % body fat is critical. Bioelectrical impedance analyzers (BIAs) are used to estimate body composition. The purpose of this study was to determine the inter-instrument reliability of 6 BIAs. The inter-instrument reliability is the ability of different instruments to produce the same results. Three types of BIAs were tested: 3 measured upper body, 2 lower body, and 1 full body bioelectrical impedance. The % body fat was estimated on a sample of 51 subjects with each of the 6 test-instruments. The sample was 58% male and ranged from 18 to 75 years of age. Body fat ranged from about 4 to 50% of body composition. The correlation coefficients (r) between test instruments ranged from 0.15 to 0.79 with a mean of 0.54. The r between BIAs was higher within than between types of BIAs. The r within the lower body types was 0.66 and within the upper body types was 0.57. In conclusion, it does not appear that there is a strong correlation between estimates of % body fat from the different Bioelectrical Impedance Analyzer test instruments in this study.