Background & aims: There is a growing need for clinically applicable body composition assessment tools for extremely obese individuals. The objective of this research was to evaluate several bioimpedance techniques for monitoring changes in fluid, particularly intracellular water (reflecting body cell mass) after bariatric surgery. Design: Fifteen extremely obese women (body mass index: 48.9 ± 7.0 kg/m2; age: 48 ± 9 years) were assessed before (baseline; T1), and approximately 6 weeks after gastric bypass surgery (T2) by several multifrequency bioelectrical impedance analysis approaches (MFBIA; QuadScan 4000), a bioimpedance spectroscopy device (BIS; Hydra 4200), and multiple dilution. Results: BIS provided intracellular water estimates that were comparable to criterion, based on mean comparisons, at both time points (T1: criterion: 24.2 ± 3.1 L, BIS: 24.0 ± 3.7 L; T2: criterion: 20.6 ± 3.7 L, BIS: 19.7 ± 3.2 L). MFBIA (with Deurenberg equations) provided comparable measures to criterion only at T2 (criterion: 20.3 ± 3.7 L, MFBIA: 20.6 ± 2.7 L). Both MFBIA (with QuadScan proprietary equations) and BIS produced estimates of intracellular water change that were comparable to dilution. There was substantial variability in individual volume measures. Conclusions: Although MFBIA and BIS hold promise as convenient techniques for assessing fluid changes, individual variability in measurements makes them impractical for assessment of extremely obese patients in the clinical setting.
Bibliographical noteFunding Information:
Grants/funding: Funding for this study was provided by the Rhoads Research Foundation of the American Society for Parenteral and Enteral Nutrition, by U.S. Public Health Service grant DK50456 which provides support for Dr. Michael Jensen's Metabolic Studies Core at the Mayo Clinic; Grant MO1-RR00400 from the National Center for Research Resources, the National Institutes of Health, which supports the General Clinical Research Center at the University of Minnesota; the Minnesota Agricultural Experiment Station; and the Midwest Dairy Association. None of the study sponsors had involvement in any aspect of the study design, data collection or analyses, or writing of this manuscript. Other contributors: We thank the study participants for their commitment to our study, and the team at the Fairview Obesity Surgery Center and the GCRC at the University of Minnesota for their ongoing support of this study. We thank Dr. Michael Jensen, Charles Ford, and Jaime Gransee at the Mayo Clinic for their assistance with the deuterium analyses. We also thank Dr. Dale Schoeller for his input on the total body water method. Statement of authorship: JM served as the study coordinator, participated in the recruitment of subjects, was involved in the collection, management, and analysis of data, and drafted the manuscript. SS participated in the collection of data, served as a study physician, and provided significant advice/consultation in study planning. TB participated in the collection of data, and served as a study physician. TK assisted with recruitment of subjects as the bariatric surgeons overseeing obesity surgery patients at the Weight Management Center. CE was the PI of the project and senior author of the manuscript, and was primarily responsible for the study design, and providing oversight of all aspects of the study. All authors read, provided feedback, and approved the final manuscript.
- Intracellular water
- Multiple frequency