ORIGINAL ARTICLE  BODY COMPOSITION, NUTRITION AND SUPPLEMENTATION 

The Journal of Sports Medicine and Physical Fitness 2019 April;59(4):632-9

DOI: 10.23736/S0022-4707.18.08505-5

Copyright © 2018 EDIZIONI MINERVA MEDICA

lingua: Inglese

Validity of electrical impedance myography to estimate percent body fat: comparison to bio-electrical impedance and dual-energy X-ray absorptiometry

Cody R. van RASSEL ¹, Nicole A. BEWSKI ¹, Erin K. O’LOUGHLIN ^{2, 3}, Alicia WRIGHT ⁴, Daniel P. SCHEEL ⁵, Lucila PUIG ⁵, Lisa KAKINAMI ^{4, 5} ✉

¹ Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada; ² INDI Department, Concordia University, Montreal, QC, Canada; ³ Hospital Research Center of Montreal University (CRCHUM), Montreal, QC, Canada; ⁴ PERFORM Center, Concordia University, Montreal, QC, Canada; ⁵ Department of Mathematics and Statistics, Concordia University, Montreal, QC, Canada

BACKGROUND: Assessment of percent body fat (%BF) is typically measured with bioelectrical impedance (BIA) as a proxy for dual-energy X-ray absorptiometry (DXA). Notably, poorer agreement between BIA and DXA among persons who are overweight or obese has been reported. The use of electrical impedance myography (EIM) as a proxy for DXA has not been validated. The objective was to evaluate an EIM device and two multi-frequency BIA devices with the reference standard (DXA) stratified by weight status and gender.
METHODS: In a convenience sample of 82 adults, %BF assessed by EIM and two BIA devices was compared to DXA. Agreement between devices was tested with intra-class correlation coefficients (ICC) and Bland-Altman plots.
RESULTS: Agreement between DXA and EIM (ICC=0.77) was poorer than the agreement between either BIA device with DXA (ICC>0.87). Stratified by sex, agreement between EIM and DXA was greater for men than women (ICC=0.81 and ICC=0.61, respectively). Stratified by BMI, agreement between EIM and DXA was best for normal-weight individuals (ICC=0.89) and progressively poorer for overweight (ICC=0.80) and obese (ICC=0.67) individuals. Bland-Altman plots revealed wide limits of agreement and an increase in EIM mean difference as average %BF increased. Similar trends were seen in BIA assessments.
CONCLUSIONS: EIM and BIA substantially underestimate %BF in overweight and obese individuals. Wide limits of agreement coupled with variable ICC limit device interchangeability with one another and limit clinical utility.

KEY WORDS: Body composition - Electric impedance - Photon absorptiometry - Adipose tissue - Myography