Validity of multi-frequency bioelectric impedance methods to measure body composition in obese patients: a systematic review

Objective Excessive lean tissue loss following bariatric surgery may pose serious metabolic consequences. Accurate methods to assess body composition following bariatric surgery are required. This review aimed to investigate if multi-frequency bioelectric impedance (MF-BI) is a valid tool to determine body composition in obese patients. Methods MEDLINE, EMBASE, CINAHL and CENTRAL databases were searched until March 2017. Included studies were published in English with obese (body mass index (BMI) ≥ 30 kg/m2) adults measuring body composition with MF-BI methods in comparison with reference methods. Exclusions were pregnancy, animal studies, non-English language studies, single frequency BI. A total of 6395 studies were retrieved. Results Sixteen studies were eligible for inclusion. Sample sizes ranged from 15 to 157, with BMI 26–48 kg/m2. MF-BI underestimated fat mass (FM) in 11 studies and overestimated fat-free mass (FFM) in nine studies in comparison with reference methods. Correlations of absolute values from MF-BI and reference methods for FM and FFM were high, however, agreement was lower at an individual level. When adjustments for BMI were made to machine algorithms, measurement accuracy improved. Significant heterogeneity was evident among included studies. Conclusions This review found that MF-BI is reliable for use at a group level. Obese-specific adjustment of algorithms for MF-BI machines increases the accuracy of absolute measures of body composition in obese individuals, improving their utility in the clinical setting. Multiple variables contributed a lack of consistency among studies included, highlighting the need for more robust studies that control confounding variables to establish clear validity assessment

Comparison of three bioelectrical impedance methods with DXA in overweight and obese men

ObjectiveTo compare bioelectrical impedance analysis (BIA) of body composition using three different methods against DXA in overweight and obese men.Research methods and proceduresForty-three healthy overweight or obese men (ages 25 to 60 years; BMI, 28 to 43 kg/m(2)) underwent BIA assessment of body composition using the ImpediMed SFB7 (version 6; ImpediMed, Ltd., Eight Mile Plains, Queensland, Australia) in multifrequency mode (Imp-MF) and DF50 single-frequency mode (Imp-SF) and the Tanita UltimateScale (Tanita Corp., Tokyo, Japan). Validity was assessed by comparison against DXA using linear regression and limits of agreement analysis.ResultsAll three BIA methods showed good relative agreement with DXA [Imp-MF: fat mass (FM), r(2) = 0.81; fat-free mass (FFM), r(2) = 0.81; percentage body fat (BF%), r(2) = 0.69; Imp-SF: FM, r(2) = 0.65; FFM, r(2) = 0.76; BF%, r(2) = 0.40; Tanita: BF%, r(2) = 0.44; all p DiscussionCompared with DXA, Imp-MF produced large bias and wide limits of agreement, and its accuracy estimating body composition in overweight or obese men was poor. Imp-SF and Tanita demonstrated little bias and may be useful for group comparisons, but their utility for assessment of body composition in individuals is limited.Ian R. Pateyjohns, Grant D. Brinkworth, Jonathan D. Buckley, Manny Noakes and Peter M. Clifto

Prediction of body water compartments in preterm infants by bioelectrical impedance spectroscopy

BACKGROUND/OBJECTIVES: To evaluate nutritional interventions in preterm infants, a simple, accurate assessment of the type of growth, that is, change in body composition through the relative contributions of lean body tissue and fat mass to weight gain, is needed. Bioelectrical impedance may provide such a method. The aim of this study was to develop resistivity coefficients appropriate for use in bioelectrical impedance spectroscopy (BIS) analysis of body water volumes in preterm infants. SUBJECTS/METHODS: A total of 99 preterm infants were enrolled (mean gestational age 32 completed weeks). Total body water (TBW) and extracellular water (ECW) were determined using the reference methods of deuterium and bromide dilution. BIS measurements taken at the same time allowed calculation of resistivity coefficients. Predictions of TBW and ECW obtained using these coefficients were then validated against volumes determined using the reference methods in a separate cohort of infants. RESULTS: Data were available for 91 preterm infants. BIS-predicted TBW and ECW correlated well with the measured volumes (Pearson’s rp=0.825 and 0.75, respectively). There was a small bias (TBW 10 ml and ECW 40 ml) but large limits of agreement (TBW±650 ml and ECW ±360 ml). CONCLUSIONS: BIS appears to have limited clinical utility; however, the relatively small bias means that it may be useful for measurements within a population or for comparisons between groups in which population means rather than individual values are compared.CT Collins, J Reid, M Makrides, BE Lingwood, AJ McPhee, SA Morris, RA Gibson and LC War