Influence of Acute Water Ingestion on Bioelectrical Impedance Analysis Estimates of Body Composition

Body composition estimation is a significant component of health and fitness assessments. Multi-frequency bioelectrical impedance analysis (MFBIA) uses multiple electrical frequencies that travel through body tissues in order to estimate fluid content and body composition. Prior to body composition assessments, it is common to implement a wet fast (i.e., a fasting period that allows water intake); however, the influence of a wet fast as compared to a dry fast (i.e., disallowing water intake) is relatively unknown. PURPOSE: To determine the effects of acute water consumption on MFBIA body composition estimates. METHODS: A randomized crossover study was conducted in 16 adults (8 F, 8 M; age: 22.0 ± 2.9 y; height: 173.6 ± 9.9 cm; weight: 74.3 ± 21.6 kg; body mass index: 24.6 ± 4.7; body fat % [BF%]: 16.7 ± 8.1%). On two occasions, participants reported to the laboratory after an overnight food and fluid fast. After a baseline MFBIA assessment, participants either consumed 11 mL/kg of bottled water (W condition) or consumed no fluid as the control (CON condition). The 11 ml/kg dose of water corresponded to absolute intakes of 531 to 1360 mL. After the water consumption time point, MFBIA tests were performed every 10 minutes for one hour. Participants stood upright for the entire research visit. MFBIA estimates of body mass (BM), fat mass (FM), fat-free mass (FFM), and BF% were analyzed using 2 x 7 (condition x time) analysis of variance with repeated measures, follow-up pairwise comparisons, and evaluation of the partial eta-squared (ηp2) effect sizes. RESULTS: No variables differed between conditions at baseline. Condition x time interactions were present for all variables (BM: pp2=0.89; FM: p=0.0008, ηp2=0.30; BF%: p=0.005, ηp2=0.23) except FFM (p=0.69, ηp2=0.03). Follow-up testing indicated that BM was ~0.6 kg higher in W as compared to CON at all post-baseline time points (pp2=0.32), regardless of condition. CONCLUSION: Up to one hour after ingestion, acute water intake was exclusively detected as increased FM by MFBIA. This contrasts with the common belief that ingesting water prior to bioimpedance tests would result in inflated FFM and decreased BF%. Since body composition estimates never returned to baseline within the hour after water ingestion, it is not clear how long this effect would persist. These results suggest acute water ingestion can produce an inflation of MFBIA body fat estimates for at least one hour. These results indicate that water intake during fasting periods should be considered as part of pre-assessment standardization

Body Fat Gain Automatically Increases Lean Mass by Changing the Fat-Free Component of Adipose Tissue

Estimating alterations in lean mass in response to various training interventions is a primary concern for many investigations. However, previous reports have suggested that lean mass estimates from weight loss interventions may be significantly altered by attempting to correct for changes in the fat-free component of adipose tissue (FFAT). This component, consisting primarily of water and protein, has been estimated as ~15% of adipose tissue (AT) mass. While a preliminary examination of this correction method has been conducted in the instance of weight loss, it has yet to be investigated after a period of purposeful weight gain and resistance training. PURPOSE: To examine the impact of corrections for FFAT on estimates of lean mass accretion during a period of weight gain and resistance training. METHODS: Twenty-one resistance trained males underwent 6 weeks of supervised training and followed a hypercaloric diet in order to elicit weight gain. Body composition was assessed pre- and post-intervention via dual energy x-ray absorptiometry (DXA). AT was estimated using DXA-derived fat mass (FM) in the equation: AT = FM/0.85. FFAT was then estimated via the equation: FFAT = 0.15 × AT. Lastly, FFAT was subtracted from DXA-derived lean mass (LMDXA) to yield the new corrected lean mass value (cLM). Changes in LMDXA and cLM in response to the training intervention were calculated, and dependent samples T-tests were employed to determine if significant differences were present between changes in LMDXA and cLM. RESULTS: Significant differences (p ≤ 0.001) were noted for estimates of LM gain, with a larger increase observed for LMDXA as compared to cLM (LMDXA :2.42 ± 1.58kg; cLM: 2.14 ± 1.65kg). CONCLUSION: Correcting DXA-derived LM for the fat-free component of adipose tissue reduces the magnitude of LM accretion after a period of weight gain. However, while LM estimates did significantly differ, the small degree to which they differed indicates questionable practical relevance of such corrections in future investigations

Impact of Fluid Consumption on Estimates of Intracellular, Extracellular, and Total Body Water from Multi-Frequency Bioelectrical Impedance Analysis

Multi-frequency bioelectrical impedance analysis (MFBIA) is able to distinguish between total body water (TBW), extracellular water (ECW) and intracellular water (ICW). Low-frequency currents are thought to primarily pass through ECW, while high-frequency currents pass through all body fluids (i.e., TBW). ICW can then be estimated by subtracting ECW from TBW. As such, MFBIA may have utility for monitoring health conditions resulting in water retention within specific fluid compartments. However, the sensitivity of fluid estimates from MFBIA is not fully established. PURPOSE: To evaluate the effects of acute fluid ingestion on body water estimates produced by a MFBIA analyzer. METHODS: Sixteen adults (8 F, 8 M; age: 22.0 ± 2.9 y; height: 173.6 ± 9.9 cm; weight: 74.3 ± 21.6 kg; body fat %: 16.7 ± 8.1%) participated in a randomized crossover study consisting of two conditions: 1) no fluid ingestion (control; C); and 2) acute ingestion of 11 mL/kg of bottled water (W). In both conditions, participants reported to the laboratory after an overnight food and fluid fast for serial assessments using 8-point standing MFBIA. An initial MFBIA assessment was performed at baseline, followed by a 5-minute period during which water was ingested (W condition) or the participant continued to rest in the lab (C condition). Beginning 10 minutes after this time period, participants were assessed by MFBIA every 10 minutes for one hour. Participants stood upright for the entirety of each research visit. Analysis of variance with repeated measures was used to examine differences in MFBIA estimates of body mass (BM), TBW, ECW, and ICW between conditions and across time. Follow-up pairwise comparisons were performed and partial eta-squared (ηp2) effect sizes were calculated. RESULTS: A group-by-time interaction was present for BM (pp2: 0.89) but not TBW (p=0.74; ηp2: 0.03), ECW (p=0.85; ηp2: 0.02), or ICW (p=0.87; ηp2: 0.05). Follow-up indicated that BM did not differ between conditions at baseline but was ~0.6 ± 0.2 kg higher in the W condition as compared to C at all post-baseline time points (pp2: 0.29 to 0.38). No significant effects were observed for ECW. CONCLUSION: The lack of change in body fluids with acute water ingestion likely indicates that: 1) within one hour, ingested water has not been assimilated into body fluids to the extent that it is detectable by MFBIA; or 2) the quantity of fluid ingestion is below the detection limits of the MFBIA analyzer. In support of the first point, it is likely that bioelectrical currents do not penetrate the gastrointestinal tract, meaning fluids contained therein are unlikely to be detected by MFBIA as fluids

The Effect of Body Composition Methodology on Resulting Energy Availability Assessments

Energy availability (EA) is defined as the total daily energy available to an individual after accounting for that expended during exercise and standardized to fat-free mass (FFM). Generally, EA values less than 30 kcal/kg FFM/day are considered “low” and have been associated with deleterious effects on reproductive and hormonal health in females. However, it is unclear whether the method used to estimate FFM influences the resulting EA values to a degree that may affect interpretation and clinical decision-making. PURPOSE: To determine the effect of FFM values derived from various methods of body composition assessment on the resulting range and interpretation of EA values. METHODS: Four EA estimates were generated in 38 healthy females (mean ± SD age: 25.6 ± 6.2 years; height: 163.6 ± 7.4 cm; weight: 64.7 ± 13.8 kg) using different combinations within a reasonable range of lower and higher (25 and 35 kcal/kg bodyweight, respectively) energy intake values and lower and higher (3.5 and 7 kcal/kg bodyweight, respectively) exercise energy expenditure values. Resulting estimates were then standardized to FFM values from air displacement plethysmography (ADP), bioelectrical impedance spectroscopy (BIS), and bioelectrical impedance analysis (BIA) from both a research-grade (multi-frequency) and consumer-grade (dual-frequency) device. Resulting EA values were then compared to those using FFM from dual-energy x-ray absorptiometry (DXA). Each estimate was assigned to one of three EA “zones”: “low” (less than 30 kcal/kg FFM), “reduced” (30-44.9 kcal/kg FFM), or “adequate” (≥45 kcal/kg FFM). Individual EA estimates that were in different zones when compared between two devices were considered discordant. RESULTS: When compared to DXA-derived estimates, EA values were discordant in up to 13-16% of individuals depending on body composition method used. Discordant values were generally more common in the plots assuming higher (35 kcal/kg bodyweight) energy intake values and were most likely to be considered “adequate” using DXA-derived FFM versus “reduced” using alternate methods. CONCLUSION: EA estimates are generally robust to the method of body composition assessment used. However, divergent interpretations may occur in a small minority of individuals in which alternate methods may provide lower EA values than DXA

Tracking Resistance Training-Induced Changes in Body Composition via 3-Dimensional Optical Scanning

Tracking changes in body composition is potentially useful for monitoring health status, disease risk, and results of lifestyle interventions. In active individuals, evaluating body composition changes over time may provide useful information regarding the effectiveness of nutrition and exercise programs. PURPOSE: The purpose of this study was to compare changes in body composition estimates obtained from a 4-compartment (4C) model and a 3-dimensional optical (3DO) scanner in resistance-trained males. METHODS: Twenty resistance-trained males underwent assessments via 4C and 3DO before and after 6 weeks of supervised resistance training plus overfeeding with a high-calorie protein/carbohydrate supplement. To generate the 4C model, tests were performed using dual-energy x-ray absorptiometry, air displacement plethysmography, and bioimpedance spectroscopy. Changes in fat mass (ΔFM) and fat-free mass (ΔFFM) detected by 3DO were compared with the reference 4C model using paired-samples t-tests, Bland-Altman analysis, equivalence testing, and evaluation of validity metrics. RESULTS: Both ΔFM (mean ± SD: 4C: 0.6 ± 1.1 kg; 3DO: 1.9 ± 1.9 kg) and ΔFFM (4C: 3.2 ± 1.7 kg; 3DO: 1.9 ± 1.4 kg) differed between methods (p \u3c 0.002). The correlation (r) for ΔFM was 0.49 (95% confidence interval [CI]: 0.06 to 0.77) and was 0.42 (95% CI: -0.03 to 0.73) for ΔFFM. The total error for ΔFM and ΔFFM estimates was 2.1 kg. ΔFFM demonstrated equivalence between methods based on a ± 2 kg (~62% of 4C change) equivalence interval, whereas ΔFM failed to exhibit equivalence even with a 100% equivalence interval. Proportional bias was observed for ΔFM but not ΔFFM. CONCLUSION: Our data indicate that changes in FM and FFM detected by a 3D scanner did not exhibit strong agreement with changes detected by a 4C model. However, within the context of our study, agreement in FFM changes was superior to agreement in FM changes based on the results of equivalence testing and lack of proportional bias in FFM changes. Therefore, depending on the level of accuracy needed, the error in FFM changes observed for the 3D scanner may be potentially acceptable for some applications. Future research should investigate the utility of 3D scanners for monitoring changes in body composition and anthropometric variables in healthy and clinical populations, as well as investigate novel body phenotypes that may be associated with disease risk or health status

Agreement Between 4-Compartment Model and 7-Site Ultrasonography for Tracking Weight Training-Induced Changes in Body Composition

Tracking body composition changes provides valuable information in a variety of contexts, including aging, disease, and lifestyle interventions. The 4-Compartment (4C) model is widely accepted as a criterion molecular-level method for evaluating body composition by integrating data from dual-energy x-ray absorptiometry (DXA), air displacement plethysmography (ADP), and bioimpedance spectroscopy (BIS). Ultrasonography (US) is another method of body composition estimation that evaluates subcutaneous adipose tissue at various body sites. PURPOSE: To evaluate the agreement between body composition changes detected by a molecular-level 4C model and a 7-site skinfold thickness-based US method in response to weight training and a hypercaloric diet. METHODS: Seventeen adult males (age:­­ 22.5 ± 2.4 y, body mass: 72.8 ± 11.6 kg, body fat % [BF%]: 14.0 ± 4.8%) who were moderately resistance-trained completed a 6-week period of supervised resistance training in conjunction with overfeeding via provision of a high-calorie, carbohydrate/protein dietary supplement. At the beginning and end of this period, body composition was evaluated via 4C model, necessitating assessments via DXA, ADP, and BIS. Additionally, body composition was estimated via US by utilizing subcutaneous adipose tissue thicknesses at seven sites on the body as described by Jackson and Pollock. Changes in fat mass (ΔFM) and fat-free mass (ΔFFM) detected by the 4C model and US were compared using paired-samples t-tests, Bland-Altman analysis, equivalence testing, and evaluation of validity metrics. RESULTS: ΔFM and ΔFFM were significantly correlated between methods (ΔFM: r=0.48 [95% confidence interval {CI}: 0.002 to 0.78]; ΔFFM: r=0.87 [95% CI: 0.66 to 0.95]. However, both ΔFM (4C: 0.6 ± 1.2 kg; US: 2.8 ± 2.5 kg) and ΔFFM (4C: 3.3 ± 1.6 kg; US: 1.0 ± 3.4 kg) significantly differed between methods (p \u3c 0.001). The total error for ΔFM and ΔFFM estimates was 3.1 kg (95% CI: 3.0 to 3.2 kg). 4C and US predicted the same direction of change in ΔFFM but not ΔFM, based on equivalence testing with an equivalence interval equal to 4C change. Proportional bias was observed for both ΔFM and ΔFFM. CONCLUSION: Although changes in body composition were correlated between methods, ΔFM and ΔFFM significantly differed between 4C and US. As compared to the 4C, US detected a greater proportion of increased body mass as FM rather than FFM. Overall, the magnitude of differences in body composition changes do not support the interchangeability of 4C and US. Although tracking body composition changes provides valuable information, it is important to take into account that different assessment methods may produce varying results in response to a given intervention

Validity of Hand-to-Foot and Foot-to-Foot Consumer Bioimpedance Analyzers: A Four-Compartment Model Comparison

Body fat percentage (BF%) is a useful variable for predicting disease risk and determining overall fitness. Consumer-grade bioimpedance analyzers seek to provide accurate body composition data while remaining affordable and accessible. PURPOSE: The purpose of this study was to compare body fat percentages obtained from hand-to-foot and foot-to-foot consumer bioimpedance analyzers to a gold standard 4-compartment (4C) model. METHODS: Seventy-five adults (40 F, 35 M; age: 27.2 ± 7.3 y; height: 168.1 ± 8.8 cm; BM: 72.1 ± 16.6 kg; 4C model BF%: 25.0 ± 9.2%) were evaluated by a 4C model, a consumer-grade hand-to-foot bioimpedance analyzer (BIA-HF; Tanita BC568) and two consumer-grade foot-to-foot bioimpedance analyzers (BIA-FF; Tanita BC554 and Tanita UM081). The 4C model comprised dual-energy X-ray absorptiometry, air displacement plethysmography, and bioimpedance spectroscopy. BF% estimates obtained by each bioimpedance analyzer were compared to the criterion 4C using the coefficient of determination (R2), standard error of the estimate (SEE), and Bland-Altman analysis. RESULTS: BIA-HF underestimated BF% by 1.4 ± 4.1%, and both BIA-FF overestimated BF% by 0.5 to 0.6 ± 5.7%. The R2 value was higher for BIA-HF as compared to both BIA-FF analyzers (0.81 vs. 0.64). The SEE and 95% limits of agreement (LOA) were lower for BIA-HF (SEE: 4.0%; LOA: 8.1%) as compared to both BIA-FF (SEE: 5.6%; LOA: 11.2%). No method demonstrated proportional bias based on Bland-Altman analysis. CONCLUSION: While both hand-to-foot and foot-to-foot consumer-grade bioimpedance analyzers demonstrated potentially meaningful errors when compared to a gold standard method, the hand-to-foot device exhibited better overall performance. Specifically, a stronger linear agreement with the 4C model and lower individual-level errors were observed with the hand-to-foot model as compared to both foot-to-foot models from the same manufacturer. The superior performance of the hand-to-foot analyzer could be due to its direct testing of both the upper and lower body, which is more similar to the methods used in the 4C model and a better representation of an individual’s overall body composition

A Between-sex Comparison of the Validity of Body Fat Percentage Estimates From Four Bioelectrical Impedance Analyzers

Bioelectrical impedance analysis (BIA) devices administer electrical currents through surface electrodes in contact with the hands and/or feet. The measured reactance and resistance of various bodily tissues to these currents are then used to estimate body fat percentage (BFP) and other body composition values of interest based on algorithms derived from validation data. Owing to different patterns of fat distribution between sexes, it is unclear whether the configuration of electrodes (i.e., hand-to-hand, foot-to-foot, or hand-to-foot) may affect the validity of these devices in males versus females. PURPOSE: The purpose of this study was to determine the validity of BFP values across four BIA devices – one consumer-grade foot-to-foot device (RENPHO Smart Bathroom Scale), one consumer-grade hand-to-hand device (Omron HBF-306), one consumer-grade octapolar device (InBody H20N), and one research-grade octapolar device (Seca mBCA 515/514) – against a criterion four-compartment model (4C), and to compare these values between males and females. METHODS: Seventy-four healthy participants (35 males and 39 females) were included in this analysis. Participants abstained from all food, fluid, caffeine, and alcohol for at least 8 hours prior to each visit. Total error (TE) was calculated as the root mean square error between the estimate of each BIA device and that of the 4C model. Standard error of the estimate (SEE) was defined as the residual standard error value from ordinary least squares regression. Constant error (CE) was calculated as the average difference between the estimate of each BIA device and that of the 4C model. RESULTS: Participants had a mean ±SD age of 27.2 ±7.3 years, height of 168.1 ±8.9 cm, weight of 72.2 ±16.7 kg, and 4C BFP of 24.9 ±9.2%. In the entire sample, ranges for validity metrics of interest were as follows: TE: 3.2% (Seca) to 7.2% (RENPHO); SEE: 3.3% (Seca) to 5.7% (RENPHO); CE: -0.02 ±3.4% (InBody) to -3.46 ±4.1% (Omron). Across all devices, both TE and SEE were lower in females, with the largest between-sex differences observed for the InBody and RENPHO. Both octapolar devices (InBody and Seca) exhibited low group-level error in males and females (all CE within ±0.32%). Meanwhile, the RENPHO and Omron devices generally underestimated BFP with a greater degree of underestimation in females (CE of -2.6% and -3.7%, respectively) than males (CE of -0.1% and -3.2%, respectively), particularly for the RENPHO. CONCLUSION: Among the four BIA devices investigated, octapolar devices tended to have higher validity overall. All devices demonstrated lower TE and SEE in females, with the greatest between-sex differences observed in the InBody and RENPHO models. Users should be aware that commercially available hand-to-hand or foot-to-foot BIA devices such as the Omron and RENPHO models used in this study may systematically underestimate BFP compared to a criterion 4C model. In contrast, hand-to-foot octapolar analyzers exhibit strong group-level validity in both sexes

Influence of Subject Presentation on Body Composition Estimates from Dual-Energy X-Ray Absorptiometry, Air Displacement Plethysmography, and Bioelectrical Impedance Analysis

Body composition assessment devices are commonly employed to track changes associated with exercise or nutritional interventions. However, many individuals undergo body composition assessments with little to no pre-testing standardization of dietary intake or physical activity, potentially introducing error into their results. PURPOSE: To examine the validity of unstandardized body composition assessments relative to standardized assessments using three common body composition assessment devices. METHODS: Twenty-three resistance-trained males (Mean ± SD; 21.6 ± 2.6 years; 71.3 ± 6.8 kg; 177.4 ± 5.9 cm; 17.4 ± 4.1% DXA-derived percent body fat [%BF]) underwent paired body composition assessments via dual-energy x-ray absorptiometry (DXA), air displacement plethysmography (ADP), and single-frequency bioelectrical impedance analysis (BIA). Each participant’s initial standardized body composition assessments were performed in the morning following an overnight food and fluid fast and 12 hours of exercise and caffeine abstention, and all unstandardized assessments were performed later during the same day following ad libitum daily activities. Unstandardized estimates of %BF and fat-free mass (FFM) for each device were compared with device-specific standardized values using paired-samples t-tests, line of identity analysis, evaluation of validity metrics, Bland-Altman analysis, and equivalence testing. RESULTS: The total error between standardized and unstandardized %BF estimates was 0.66% for DXA [95% confidence interval {CI}: 0.56-0.76%], 1.60% for ADP [95% CI: 1.50-1.70%], and 1.85% for BIA [95% CI: 1.75-1.95%]. The total error for FFM estimates was 0.75kg for DXA [95% CI: 0.65-0.85kg], 1.15kg for ADP [95% CI: 1.06-1.25kg], and 1.68 kg for BIA [95%CI: 1.58-1.78]. %BF estimates did not differ between paired measurements for DXA (p = 0.17) or ADP (p = 0.10) but differed between BIA (p \u3c 0.001) assessments. Similarly, FFM estimates did not differ between paired measurements for DXA (p = 0.40) or ADP (p = 0.78) but differed between BIA assessments (p \u3c 0.001). All paired assessments for each outcome produced regression line slopes which differed from the line of identity (p \u3c 0.001). Only BIA %BF estimates exhibited an intercept that differed from the line of identity (p \u3c 0.001). No proportional bias was detected for any outcome. Equivalence was demonstrated between %BF estimates for DXA but not ADP or BIA, based on a ±1%BF equivalence interval. Equivalence was demonstrated for all FFM estimates except BIA, based on a ±1kg equivalence interval. CONCLUSION: Our findings suggest that DXA body composition estimates are more robust when conducted in an unstandardized state relative to ADP or BIA. These results can inform the choice of body composition assessment methodology when pre-testing standardization is not possible

Day-to-Day Precision Error and Least Significant Change for Two Commonly Used Bioelectrical Impedance Analysis Devices

Bioelectrical impedance analysis (BIA) devices administer electrical currents through surface electrodes to estimate overall body fluids from the measured resistance and reactance of bodily tissues. The proportion of fat versus fat-free mass can be further estimated by these devices using algorithms developed from reference data. BIA devices are commonly used in field as well as laboratory settings due to their convenience, ease of use, and relatively low cost. PURPOSE: The purpose of this study was to determine the day-to-day precision error (PE) and least significant change (LSC) of the percent body fat (PBF), fat mass (FM), and fat-free mass (FFM) estimated by two commonly used BIA devices, the InBody 770 and the Omron HBF-306. METHODS: Seventeen healthy participants (7 males, 10 females) were included in this analysis. Participants visited the laboratory on two separate occasions no more than 48 hours apart and abstained from all food, fluid, caffeine, and alcohol for at least 8 hours prior to each visit. Height and weight were measured using a Seca 769 stadiometer and digital scale. PE was calculated as , where SD is the within-subject standard deviation. LSC was calculated as 2.77 * PE to reflect a 95% confidence level. RESULTS: Participants had a mean ±SD age of 27.1 ±8.3 years, height of 171.6 ±8.5 cm, and weight of 68.0 ±10.6 kg. PE for the InBody was 1.0%, 0.7 kg, and 0.9 kg for PBF, FM, and FFM, respectively; PE for the Omron was 0.6%, 0.4 kg, and 0.6 kg for the same variables. The LSC values of each variable for the InBody were 2.8%, 1.9 kg, and 2.4 kg for PBF, FM, and FFM, respectively; the LSC values for these variables were 1.5%, 1.0 kg, and 1.6 kg for the Omron device. CONCLUSION: Individuals looking to use BIA as a method of detecting true changes in body composition over time should be aware that day-to-day measurement error between estimates were as as high as 1.0% for body fat, 0.7 kg for fat mass, and 0.9 kg for fat-free mass in the current study; therefore, changes within these parameters likely reflect error of measurement and not true physiological differences. Additionally, changes over time between estimates from an InBody 770 device should meet or exceed a difference of at least 2.8% body fat, 1.9 kg FM, or 2.4 kg FFM to increase confidence that the differences are a reflection of physiological changes rather than between-day measurement error; differences between readings from an Omron should meet or exceed 1.5% body fat, 1.0 kg FM, or 1.6 kg FFM for this purpose. The InBody 770 demonstrated higher precision error and thus may entail a higher least significant change to meaningfully detect true physiological changes between time points. However, the observed differences in these values between the InBody 770 and Omron HBF-306 may also indicate that the InBody 770 is more sensitive to small but real changes in bioelectrical impedance values between days. Longitudinal studies are needed to elucidate the comparative tracking validity of these commonly used BIA devices in healthy populations