The Comparison of Segmental Multifrequency Bioelectrical Impedance Analysis and Dual-Energy X-ray Absorptiometry for Estimating Fat Free Mass and Percentage Body Fat in an Ambulatory Population

JPEN J Parenter Enteral Nutr. 2021 Aug;45(6):1231-1238. doi: 10.1002/jpen.1994. Epub 2020 Sep 10.


Background: Despite malnutrition being associated with increased mortality and morbidity, there continues to be great difficulty in defining criteria and implementing widespread screening. Tools used to diagnose decreased fat-free mass (FFM [sarcopenia]) should be easy to use, relatively inexpensive, and safe. Bioelectrical impedance analysis (BIA) has the potential to meet these criteria, but reliability across body mass index (BMI) classes is a concern.

Methods: A total of 176 healthy ambulatory participants (aged 18-65 years) were recruited equally (n = 44) in 4 BMI categories: (1) 18.5-24.9, (2) 25.0-29.9, (3) 30-34.9, and (4) ≥35.0. Participants were fasting overnight and had S-MFBIA (InBody 770) measurements the next morning, with DXA being performed subsequently within 30 minutes.

Results: The measurement (mean ± SD) for FFM with DXA was 52.8 ± 11.0, and BIA was 53.6 ± 11.0. Delta (S-MFBIA vs DXA) was 0.8 ± 2.2 (5% limits of agreement -3.5 to +5.2), and concordance correlation coefficient (CCC) was 0.98 (95% CI, 0.97-0.98). The measurements (mean ± SD) for PBF with DXA was 37.5 ± 10.6% and S-MFBIA was 36.6 ± 11.3%. Delta (S-MFBIA vs DXA) was -0.9 ± 2.6 (5% limits of agreement 6.0 to +4.2), and CCC was 0.97 (95% CI, 0.96-0.98). The CCC according to the 4 BMI groups for FFM and PBF was between 0.96-0.98 and 0.90-0.94, respectively.

Conclusions: FFM and PBF measured by S-MFBIA had good agreement with DXA across all BMI categories measured in the current study of ambulatory participants.

Keywords: Fat-free mass; bioelectrical impedance analysis; body composition; dual-energy x-ray absorptiometry; enteral nutrition; percentage body fat.