Submitted to: Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/7/2008
Publication Date: 1/15/2009
Citation: Shafer, K.J., Siders, W.A., Johnson, L.K., Lukaski, H.C. 2009. Validity of segmental multiple-frequency bioelectrical impedance analysis to estimate body composition of adults across a range of body mass indexes. Nutrition. 25(1):25-32.
Interpretive Summary: The public health epidemic of rising obesity has prompted numerous interventions to facilitate healthy weight management. Techniques that provide valid assessment data among individuals of varying levels of body fatness are critical for evaluating efficacy of these interventions. Use of segmental, multiple-frequency bioelectrical impedance analysis (MF-BIA) may offer an advantage for body composition assessment, in particular, in obese individuals. However, the validity of this method at estimating body composition among individuals of varying levels of adiposity is not well established. This study compared estimates of body composition determined by using an eight-electrode, segmental, MF-BIA device and the reference dual x-ray absorptiometry (DXA) in healthy adults stratified into three groups, based on body mass index (BMI). Percent body fat, fat-mass, and fat-free mass were measured by DXA and segmental MF-BIA in 132 healthy adults classified by normal, overweight, and obese BMI. Compared to DXA, percent body fat and fat mass were significantly overestimated and fat-free mass significantly underestimated by MF-BIA in obese individuals. In the normal BMI group, MF-BIA significantly underestimated percent body fat and fat mass and significantly overestimated fat-free mass. MF-BIA significantly overestimated fat mass and fat-free mass in overweight individuals, but percent body fat was not different between methods. Differences in percent body fat between MF-BIA and DXA increased significantly as percent body fat increased. Waist circumference was the only significant predictor of the error in percent body fat between MF-BIA and DXA. Segmental, MF-BIA is an accurate method to estimate percent body fat among individuals with a BMI in the normal and overweight ranges, but not in the obese range. Further research on the effect waist circumference or body fat distribution has on the accuracy of impedance measurements is needed.
Technical Abstract: Objective: Compare estimates of body composition using segmental, multiple frequency bioelectrical impedance analysis (MF-BIA) with dual x-ray absorptiometry (DXA) in healthy adults across a range of body mass index (BMI). Methods: Percent body fat (%BF), fat-mass (FM), and fat-free mass (FFM) assessed by DXA and segmental MF-BIA in 132 healthy adults classified by normal (NO; 18.5-24.9 kg/m2), overweight (OW; 25-29.9 kg/m2), and obese (OB; 30-39.9 kg/m2) BMI. Results: Compared to DXA, MF-BIA overestimated %BF (3.4%; p<.0001) and FM (4.1 g; p<.0001), and underestimated FFM (-1.9 g; p<.0001) in the OB group, and underestimated %BF (-1.6%; p<.0001) and FM (-0.69 g; p>.04), and overestimated FFM (2.1 g; p<.0001) in the NO group. In the OW group, MF-BIA overestimated FM (0.95 g; p>.006) and FFM (0.71 g;p>.04); %BF was not different between methods. Differences in %BF between MF-BIA and DXA increased as %BF increased (r=.42, p<.0001). Waist circumference was the only significant predictor of systematic error in %BF between MF-BIA and DXA, explaining 36% of the variance (p<.0001). Conclusions: Segmental, MF-BIA is a valid method to estimate %BF among NO and OW BMI, but not in OB. Further examination of the effect waist circumference or body fat distribution has on the accuracy of BIA measurements is warranted.