Evaluating of altered hydration status on effectiveness of body composition analysis using bioelectric impedance analysis

The Effect of Passive Dehydration on Phase Angle and Body Composition: A Bioelectrical Impedance Analysis

Bioelectrical impedance analysis (BIA) is a method used to estimate body composition, and it relies mainly on the body's water content. Insufficient body water can introduce bias to body composition scores.

PURPOSE

To determine the effect of body weight loss elicited by passive dehydration on body composition scores, including phase angle (PhA).

METHODS

Twenty-five euhydrated apparently healthy and physically active men's (age = 22.6 ± 3.3 yr.; body mass = 76.7 ± 15.9 kg; height = 172.0 ± 6.3 cm) body composition variables and PhA were measured before and after sitting quietly for 5 h in a controlled environment (26.6 ± 1.7 °C, 72 ± 4.9%RH).

RESULTS

It was found that five hours of passive dehydration caused a loss in body weight (Δ = 0.76 ± 0.34 kg, p < 0.05) and a decrease in body fat estimation (Δ = 0.90 ± 0.87 kg, p < 0.001). Additionally, an increase in ECW (Δ = 0.12 ± 0.30 L, p < 0.021) and PhA (Δ = 0.10 ± 0.15°, p < 0.005) was observed.

CONCLUSION

Body weight loss due to passive dehydration decreased BIA-derived fat mass, and increased extracellular water and PhA in physically active and apparently healthy men. Nonetheless, these changes had a negligible effect on the accuracy of the equipment, rendering them clinically insignificant.

Validity and agreement between dual-energy X-ray absorptiometry, anthropometry and bioelectrical impedance in the estimation of fat mass in young adults

Introduction

Assessment of fat mass has historically employed various methods like Dual-energy X-ray Absorptiometry (DXA), and bioelectrical impedance (BIA), and anthropometry with its set of formulas. However, doubts persist regarding their validity and interchangeability to evaluate fat mass. This research aimed to determine the validity of anthropometry, and BIA in estimating fat mass Vs DXA, considering the influence of sex and hydration status.

Methods

A descriptive, cross-sectional study included 265 young adults (161 males and 104 females), assessed through DXA, BIA in a standing position, and anthropometry. A fat mass estimation formula with DXA, a fat mass estimation formula with BIA and 10 fat mass estimation formulas with anthropometry were calculated.

Results

Significant differences were found across DXA, BIA and anthropometry in both kilograms and percentages for the overall sample (p<0.001), and when the covariable sex was included (p<0.001), with no significant effect of hydration status (p=0.332-0.527). Bonferroni-adjusted analyses revealed significant differences from DXA with anthropometry and BIA in most cases for the overall sample (p<0.001), as well as when stratified by sex (p<0.001-0.016). Lin's coefficient indicated poor agreement between most of the formulas and methods both in percentage and kilograms of fat mass (CCC=0.135-0.892). In the Bland-Altman analysis, using the DXA fat mass values as a reference, lack of agreement was found in the general sample (p<0.001-0.007), except for Carter's formula in kilograms (p=0.136) and percentage (p=0.929) and Forsyth for percentage (p=0.365). When separating the sample by sex, lack of agreement was found in males for all methods when compared with both percentage and kilograms calculated by DXA (p<0.001). In the female sample, all methods and formulas showed lack of agreement (p<0.001-0.020), except for Evans's in percentage (p=0.058).

Conclusion

The formulas for fat mass assessment with anthropometry and BIA may not be valid with respect to the values reported with DXA, with the exception of Carter's anthropometry formula for general sample and Evans's anthropometry formula for female sample. BIA could also be an alternative if what is needed is to assess fat mass in women as a group.

Efficacy and safety of prolonged water fasting: a narrative review of human trials

The goal of this narrative review is to summarize the effects of prolonged fasting on various metabolic health measures, including body weight, blood pressure, plasma lipids, and glycemic control. Prolonged fasting is characterized by consciously eating little to no food or caloric beverages for several days to weeks. Results reveal that prolonged fasting for 5-20 days produces potent increases in circulating ketones, and mild to moderate weight loss of 2-10%. Approximately two-thirds of the weight lost is lean mass, and one-third is fat mass. The excessive lean mass loss suggests that prolonged fasting may increase the breakdown of muscle proteins, which is a concern. Systolic and diastolic blood pressure consistently decreased with prolonged fasting. However, the impact of these protocols on plasma lipids is less clear. While some trials demonstrate decreases in LDL cholesterol and triglycerides, others show no benefit. With regard to glycemic control, reductions in fasting glucose, fasting insulin, insulin resistance, and glycated hemoglobin (HbA1c) were noted in adults with normoglycemia. In contrast, these glucoregulatory factors remained unchanged in patients with type 1 or type 2 diabetes. The effects of refeeding were also examined in a few trials. It was shown that 3-4 months after the fast was completed, all metabolic benefits were no longer observed, even when weight loss was maintained. With regard to adverse events, metabolic acidosis, headaches, insomnia, and hunger were observed in some studies. In summary, prolonged fasting appears to be a moderately safe diet therapy that can produce clinically significant weight loss (>5%) over a few days or weeks. However, the ability of these protocols to produce sustained improvements in metabolic markers warrants further investigation.

Peak Week Carbohydrate Manipulation Practices in Physique Athletes: A Narrative Review

BACKGROUND

Physique athletes are ranked by a panel of judges against the judging criteria of the corresponding division. To enhance on-stage presentation and performance, competitors in certain categories (i.e. bodybuilding and classic physique) achieve extreme muscle size and definition aided by implementing acute "peaking protocols" in the days before competition. Such practices can involve manipulating nutrition and training variables to increase intramuscular glycogen and water while minimising the thickness of the subcutaneous layer. Carbohydrate manipulation is a prevalent strategy utilised to plausibly induce muscle glycogen supercompensation and subsequently increase muscle size. The relationship between carbohydrate intake and muscle glycogen saturation was first examined in endurance event performance and similar strategies have been adopted by physique athletes despite the distinct physiological dissimilarities and aims between the sports.

OBJECTIVES

The aim of this narrative review is to (1) critically examine and appraise the existing scientific literature relating to carbohydrate manipulation practices in physique athletes prior to competition; (2) identify research gaps and provide direction for future studies; and (3) provide broad practical applications based on the findings and physiological reasoning for coaches and competitors.

FINDINGS

The findings of this review indicate that carbohydrate manipulation practices are prevalent amongst physique athletes despite a paucity of experimental evidence demonstrating the efficacy of such strategies on physique performance. Competitors have also been observed to manipulate water and electrolytes in conjunction with carbohydrate predicated on speculative physiological mechanisms which may be detrimental for performance.

CONCLUSIONS

Further experimental evidence which closely replicates the nutritional and training practices of physique athletes during peak week is required to make conclusions on the efficacy of carbohydrate manipulation strategies. Quasi-experimental designs may be a feasible alternative to randomised controlled trials to examine such strategies due to the difficulty in recruiting the population of interest. Finally, we recommend that coaches and competitors manipulate as few variables as possible, and experiment with different magnitudes of carbohydrate loads in advance of competition if implementing a peaking strategy.

Body composition measured by multi-frequency bioelectrical impedance following creatine supplementation

BACKGROUND

Acute fluid ingestion increases estimated body fat percentage (BF%) measurements by single frequency (SF-BIA) and multi-frequency bioelectrical impedance (MF-BIA). It is unknown if MF-BIA accurately measures total BF% and total body water (TBW) after creatine supplementation, which causes fluid retention, and resultant increases in fat-free mass and TBW. The purpose of this study was to analyze the effect of creatine supplementation on body composition and TBW measured through a popular MF-BIA device (InBody 770).

METHODS

Thirteen male and 14 female subjects (18-22 years) completed one week of creatine monohydrate (0.3 g/kg body weight) or maltodextrin. Pre- and post-supplementation body composition measurements included dual-energy X-ray absorptiometry (DEXA), SF-BIA measured by an Omron HBF-306C device, and MF-BIA measured by an InBody 770 device to measure BF%, fat free mass (FFM), and fat mass (FM). Additionally, intracellular water (ICW), extracellular water (ECW), and TBW were estimated by MF- BIA.

RESULTS

FFM increased more in the creatine group than the placebo group measured by all body composition modes (1.2 kg, 1.9 kg, and 1.1 kg increase for SF-BIA, MF-BIA, and DEXA respectively, P<0.05). Creatine supplementation resulted in a 2% increase (P<0.05) in TBW measured by MF-BIA (40.4±9.5 to 41.2±9.6 kg).

CONCLUSIONS

One week of creatine supplementation increased TBW as detected by the InBody 770 device. Changes in body composition that occurred due to the increase in TBW were detected as an increase in FFM measured by SF-BIA, MF-BIA, and DEXA.

A comparison of bioelectrical impedance analysis and air displacement plethysmography to assess body composition in children

Background

Accurate assessment of body composition (BC) is important to investigate the development of childhood obesity. A bioelectrical impedance analysis (BIA) device is portable and inexpensive compared with air displacement plethysmography (ADP) for the assessment of BC and is widely used in children. However, studies of the effectiveness of BIA are few and present different results, especially in pediatric populations. The aim of this study was to evaluate the agreement between BIA and ADP for estimating BC.

Methods

The BC of 981 Chinese children (3-5 years) was measured using the BIA device (SeeHigher BAS-H, China) and ADP (BOD POD).

Results

Our results showed that BIA underestimated fat mass (FM) and overestimated fat-free mass (FFM) in normal weight children (P < 0.05), but the opposite trend was shown in children with obesity (P < 0.05). The agreement between FM and FFM measured by the two methods was strong (CCC > 0.80). The linear regression equation of 5-year-old children was constructed.

Conclusion

The SeeHigher BAS-H multi-frequency BIA device is a valid device to evaluate BC in Chinese preschool children compared with ADP (BOD POD), especially in 5-year-old children or children with obesity. Further research is needed to standardize the assessment of BC in children.

Sarcopenic obesity research perspectives outlined by the sarcopenic obesity global leadership initiative (SOGLI) - Proceedings from the SOGLI consortium meeting in rome November 2022

The European Society for Clinical Nutrition and Metabolism (ESPEN) and the European Association for the Study of Obesity (EASO) launched the Sarcopenic Obesity Global Leadership Initiative (SOGLI) to reach expert consensus on a definition and diagnostic criteria for Sarcopenic Obesity (SO). The present paper describes the proceeding of the Sarcopenic Obesity Global Leadership Initiative (SOGLI) meeting that was held on November 25th and 26th, 2022 in Rome, Italy. This consortium involved the participation of 50 researchers from different geographic regions and countries. The document outlines an agenda advocated by the SOGLI expert panel regarding the pathophysiology, screening, diagnosis, staging and treatment of SO that needs to be prioritized for future research in the field.

Lower calcium and iron intake in adolescent gymnasts: A case of concern for youth sports nutrition

OBJECTIVES

Diet is important for the appropriate development and maturation of young amateur athletes. The aim of this study was to determine whether young gymnasts were consuming adequate amounts of nutrients, particularly calcium and iron.

METHODS

This cross-sectional survey was conducted in Portugal's Almada and Lisbon regions in 2020. To determine if participants' diet was adequate, weight, height, and skinfold measurements were taken. Dietary consumption was examined using two 24-h recalls. We collected data from 66 participants (60% females, 12-18 y of age), of whom 82% had normal weight and 39% had ideal body fat.

RESULTS

The daily total energy intake (TEI) was1605 ± 601 kcal. Of the TEI, 19%, 31%, and 50% were comprised of protein, fat, and carbohydrates, respectively. The most often consumed protein sources were poultry and ultra-processed meat products (52% and 45%, respectively). The average daily consumption of calcium and iron was 626 ± 293 and 9 ± 3 mg, respectively. Only 2 of the 66 participants had calcium intake within recommended levels, and 1of 5 had iron intake within recommended levels, the percentage of which was lower in girls than boys (7.5% versus 38.5%, P < 0.05).

CONCLUSIONS

Despite having a sufficient macronutrient distribution, Portuguese gymnasts consume a high amount of ultra-processed items and a low amount of calcium and iron. The low proportion of female gymnasts with adequate iron consumption is cause for worry in sports nutrition.

Detecting low-intake dehydration using bioelectrical impedance analysis in older adults in acute care settings: a systematic review

BACKGROUND

Dehydration is a frequent cause of excess morbidity and poor health outcomes, particularly in older adults who have an increased risk of fluid loss due to renal senescence, comorbidities, and polypharmacy. Detecting dehydration is key to instigating treatment to resolve the problem and prevent further adverse consequences; however, current approaches to diagnosis are unreliable and, as a result, under-detection remains a widespread problem. This systematic review sought to explore the value of bioelectrical impedance in detecting low-intake dehydration among older adults admitted to acute care settings.

METHODS

A literature search using MEDLINE, EMBASE, CINAHL, Web of Science, and the Cochrane Library was undertaken from inception till May 2022 and led to the eventual evaluation of four studies. Risk of bias was assessed using the Cochrane tool for observational studies; three studies had a high risk of bias, and one had a low risk. Data were extracted using systematic proofs. Due to insufficient reporting, the data were analysed using narrative synthesis.

RESULTS

One study showed that the sensitivity and specificity of bioelectrical impedance in detecting low-intake dehydration varied considerably depending on the total body water percentage threshold used to ascertain dehydration status. Other included studies supported the technique's utility when compared to conventional measures of hydration status.

CONCLUSIONS

Given the scarcity of literature and inconsistency between findings, it is not possible to ascertain the value of bioelectrical impedance for detecting low-intake dehydration in older inpatients.

Changes in the body composition of boys aged 11-18 years due to COVID-19 measures in the Czech Republic

BACKGROUND

The lockdown measures related to coronavirus disease 2019 (COVID) impacted the health of adolescents by reducing physical activity (PA). The physical changes in response to decreases in PA can be measured with full body composition analysis. The aim of this study was to evaluate the effects of long-term PA restrictions on body fat (BF), fat-free mass (FFM) and skeletal muscle mass (SMM) in adolescents.

METHODS

A total of 1669 boys (before PA restriction (G1): 998; after PA restrictions ended (G2): 671; between the ages of 11 and 18 were included. The measured parameters were body mass (BM), visceral fat area (VFA), BF, FFM and SMM. The whole-body composition was evaluated using bioelectrical impedance analysis (BIA).

RESULTS

Compared to G1, G2 exhibited an increase in BF between 1.2 and 5.1%. This difference was significant in boys aged 13 to 18 years (p < 0.05). VFA increased between 5.3 and 20.5 cm²; this increase was significant in boys aged 13 to 18 years (p < 0.05). SMM decreased between 2.6 and 3.8%, and this decrease was significant in all age groups (p < 0.05). Changes in body composition were not accompanied by any significant changes in BM.

CONCLUSIONS

COVID-19 restrictions reduced PA, resulting in a significant decrease in SMM. This decrease may impact boys' ability to engage in sufficiently varied PA, which may lead to a further decline in PA and subsequent medical consequences in adulthood.

Endothelial Damage and Muscle Wasting in Cardiac Surgery Patients

This is a post-hoc analysis to assess the effect of anesthesia, surgical trauma, and extracorporeal circuit on endothelial integrity, microvascular permeability, and extracellular fluid balance, as well as on skeletal muscle catabolism, in patients undergoing elective cardiac surgery. We included 127 well-nourished patients undergoing “on-pump” elective cardiac surgery. One day prior to surgery (D0) and again on postoperative day 7 (POD7), body mass index, body composition assessment, hand-grip strength (HGS), and mid-upper arm muscle circumference (MAMC) were measured. Patients were assigned to early recovery (ER) and late recovery (LR) groups, depending on the duration of ICU stay (cut-off 48 hours). The magnitude of change (Δ) in all parameters studied was assessed in ER versus LR groups, regarding (i) epithelial tissue dysfunction (Δ-Extra-Cellular Water percentage (Δ-ECW%), Δ-Phase Angle (Δ-PhA)), (ii) skeletal muscle mass catabolism (Δ-Skeletal muscle mass reduction%, Δ-Hand Grip Strength (Δ-HGS) and Δ-Mid Upper-Arm Muscle Circumference (Δ-MAMC)). Baseline measurements were similar in both groups. A significant difference was observed in all Δ-parameters studied (Δ-ECW%, Δ-PhA and muscle catabolism, Δ-HGS, Δ-MAMC), the worse results being correlated to the LR group. The results raise the issue that patients with early recovery may silently have pathological conditions, continuing even on the day of discharge - further research should be planned.

Acute Water Supplementation Improved the Body Composition of Young Female Adults After Water Restriction of 12 h in Baoding, China: A Randomized Controlled Trial (RCT)

Insufficient intake of water may influence the balance of water in the human body. In this study, we explore the impacts of water supplementation on body composition indices among young adults after 12 h of water restriction, with the aim to determine the optimum volume of water for improving body water composition. A randomized controlled trial study was conducted among 64 young men and women in Baoding, China. After fasting overnight for 12 h, anthropometric measurements and urine and blood samples were collected as a baseline test at 8:00 a.m. of Day 2. Body composition was determined by measuring the ECW (extracellular water), ICW (intracellular water), and TBW (total body water) through bioelectrical impedance analysis (BIA). The participants were randomly divided into four groups, including water supplementation (WS) groups 1, 2, and 3, with 500, 200, and 100 mL of water, respectively, and a no water supplementation (NW) group. After 90 min, they were reassessed in a rehydration test (at 10:00 a.m. of Day 2). Repeated measurement ANOVA was used to assess the impact of water supplementation on body composition. Comparing the baseline and rehydration tests, interactions between time and volume were not significant among the men (all p > 0.05). Among women, a significant interaction was only found in ECW (p = 0.043), with TBW tending toward being significant (p = 0.055). Comparing the baseline and rehydration tests, the ECW in WS group 1, WS group 3, and the NW group all decreased (p = 0.028, p = 0.001, and p = 0.029), with reductions of 0.1, 0.3, and 0.2 kg, respectively; however, no significant decrease was observed in WS group 2 (p = 0.329). Furthermore, comparing the WS groups with the NW group in the rehydration test, the differences were not significant (p = 1.000, p = 1.000, and p = 0.288, respectively). Between men and women within groups, all of the body composition indices differed significantly, both at baseline and rehydration tests (all p < 0.05). Water supplementation led to changes in the distribution of the water content in young female adults in this study-but not men-after 12 h of water restriction, with no decrease in ECW. Finally, we found that 200 mL was the minimum volume capable of improving the water content distribution in participants in this study.

Trial Registration

[www.chictr.org.cn], identifier [ChiCTR-IOR-17011568].

Physical activity and adiposity in preschool children: The Barwon Infant Study

BACKGROUND

The association between physical activity and adiposity in preschool-aged children is unclear.

OBJECTIVE

To assess the cross-sectional association between objectively measured physical activity and body fat in preschool-aged children.

METHODS

In the preschool review in an Australian birth cohort study (n = 1074), mean duration and time accumulated in ≥1-min bouts of physical activity at light-intensity (LPA), moderate- to vigorous-intensity (MVPA) and light- to vigorous-intensity (LMVPA) were computed from accelerometer (ActiGraph GT3X+) data. Percent body fat was assessed by bioelectrical impedance. Associations between physical activity and percent body fat were examined by multiple regression, adjusted for accelerometer wear time, MVPA (in analyses of LPA), maternal body mass index (BMI) and maternal education.

RESULTS

A total of 450 participants (n = 450) had valid data. There was evidence of associations between physical activity and adiposity: each additional hour of LVPA was associated with 0.6% (CI₉₅ -0.2%, 1.3%) higher body fat; ≥1-min bouts of LPA was associated with 1.0% (CI₉₅ 0.1%, 1.9%) higher body fat; each additional hour of MVPA was associated with -0.8% (CI₉₅ -1.6%, -0.1%) less body fat; and ≥1-min bouts of MVPA was associated with -1.3% (CI₉₅ -2.5%, -0.1%) body fat.

CONCLUSIONS

Among a cohort of preschool-aged children, there was evidence that more intensive physical activity assessed by an accelerometer is associated with reduced body fat.

Bioelectrical Impedance Changes of the Trunk are Opposite the Limbs Following Acute Hydration Change

This study aimed to evaluate the changes in impedance and estimates of body composition variables obtained from segmental multi-frequency bioelectrical impedance analysis (SMFBIA) following acute hydration change. All participants (N = 11 active adults) had SMFBIA measurements at baseline (euhydration), post-dehydration, and post-hyperhydration in an experimental repeated-measures design. Dehydration and hyperhydration trials were randomized with the opposite treatment given 24 h later. Dehydration was achieved via a heat chamber of 40 °C and 60% relative humidity. Hyperhydration was achieved by drinking lightly-salted water (30 mmol·L^-1 NaCl; 1.76 g NaCl·L^-1) within 30 min. Post-measurements were taken 30 min after each treatment. Despite changes in mass post-dehydration (Δ = -2.0%, p < 0.001) and post-hyperhydration (Δ = 1.2%, p < 0.001), SMFBIA estimates of total body water (TBW) did not change significantly across trials (p = 0.507), leading to significant differences (p < 0.001) in SMFBIA-estimates of body fat percentage across trials. Dehydration resulted in a significant (p < 0.001) 8% decrease in limb impedances at both 20 kHz and 100 kHz. Hyperhydration increased limb impedances only slightly (1.5%, p > 0.05). Impedance changes in the trunk followed an opposite pattern of the limbs. SMFBIA failed to track acute changes in TBW. Divergent impedance changes suggest the trunk is influenced by fluid volume, but the limbs are influenced by ion concentration.

Evaluation of the Relationships between Simple Anthropometric Measures and Bioelectrical Impedance Assessment Variables with Multivariate Linear Regression Models to Estimate Body Composition and Fat Distribution in Adults: Preliminary Results

BACKGROUND

Overweight and obesity are conditions associated with sedentary lifestyle and accumulation of abdominal fat, determining increased mortality, favoring chronic diseases, and increasing cardiovascular risk. Although the evaluation of body composition and fat distribution are highly relevant, the high cost of the gold standard techniques limits their wide utilization. Therefore, the aim of this work was to explore the relationships between simple anthropometric measures and BIA variables using multivariate linear regression models to estimate body composition and fat distribution in adults.

METHODS

In this cross-sectional study, sixty-eight adult individuals (20 males and 48 females) were subjected to bioelectrical impedance analysis (BIA), anthropometric measurements (waist circumference (WC), neck circumference (NC), mid-arm circumference (MAC)), allowing the calculation of conicity index (C-index), fat mass/fat-free mass (FM/FFM) ratios, body mass index (BMI) and body shape index (ABSI). Statistical analyzes were performed with the R program. Nonparametric Statistical tests were applied to compare the characteristics of participants of the groups (normal weight, overweight and obese). For qualitative variables, the Fisher's exact test was applied, and for quantitative variables, the paired Wilcoxon signed-rank test. To evaluate the linear association between each pair of variables, the Pearson correlation coefficient was calculated, and Multivariate linear regression models were adjusted using the stepwise variable selection method, with Akaike Information Criterion (p ≤ 0.05).

RESULTS

BIA variables with the highest correlations with anthropometric measures were total body water (TBW), body fat percentage (BFP), FM, FFM and FM/FFM. The multiple linear regression analysis showed, in general, that the same variables can be estimated through simple anthropometric measures.

CONCLUSIONS

The assessment of fat distribution in the body is desirable for the diagnosis and definition of obesity severity. However, the high cost of the instruments (dual energy X-ray absorptiometry, hydrostatic weighing, air displacement plethysmography, computed tomography, magnetic resonance) to assess it, favors the use of BMI in the clinical practice. Nevertheless, BMI does not represent a real fat distribution and body fat percentage. This highlights the relevance of the findings of the current study, since simple anthropometric variables can be used to estimate important BIA variables that are related to fat distribution and body composition.

Body Composition Results of Caucasian Young Normal Body Mass Women in the Follicular Proliferative Phase, Measured for the Different Positions of Limbs

The bioelectrical impedance analysis (BIA) became a standardized technique for assessing body composition, but many factors affect the reproducibility of measurement, including body and limbs position. In spite of the fact that it is recommended for patient to be in a supine position, with arms abducted at least 30° and legs abducted at approximately 45°, a lot of authors conduct their measurements with arms and legs of patients separated to not touch the body but not strictly following the recommendations. Taking this into account, the aim of the study was to analyze the body composition results of Caucasian young normal body mass women in the follicular proliferative phase, measured for the different positions of limbs in order to compare the results obtained in the recommended position (with arms abducted at least 30° and legs abducted at approximately 45°) and in the commonly used position (not following strictly the recommendations). The study was conducted in a homogenous group of 100 adult females under the age of 30 years using BIA 101/ASE with the Bodygram Pro software and its equations by Akern Srl, Firenze, Italy, based on the measurement recommendations. The measurements were conducted (1) in a recommended position of arms abducted at least 30° and legs abducted at approximately 45° and (2) with arms spread and legs separated to not touch the body to compare the body composition assessment (fat mass, fat-free mass, body cell mass, muscle mass, water content, extracellular water content, and intracellular water content). It was stated that the results obtained for various positions of limbs were positively correlated (p < 0.0001; R > 0.5). At the same time, the statistically significant differences dependent on the position were observed for the calculated results of body cell mass (lower results for the recommended position for the results observed in kg and % of body mass; p = 0.0165 and p = 0.0075, respectively) and muscle mass (lower results for the recommended position for the results observed in kg and % of body mass; p = 0.0025 and p = 0.0011, respectively), as well as extracellular and intracellular water (higher % of total body water for the extracellular water and lower for intracellular water; p = 0.0049 and p = 0.0115, respectively), resulting from the measured resistance and reactance values. For all listed comparisons of significantly differing variables, weighted κ statistics indicated moderate agreement (values of 0.41–0.60), and the Bland–Altman plot analysis indicated no agreement (Bland–Altman index of >5%). While compared with the reference values, the major differences were observed for extracellular/intracellular water content, as, while applying a method with arms and legs separated to not touch the body (not recommended position), the extracellular water content was underestimated for 31% and intracellular water content was overestimated for 28% of participants. It may be concluded that the recommended body position of arms abducted at least 30° and legs abducted at approximately 45° should be chosen to ensure the reliability of the BIA measurements, as, while the recommendations of a body position are not followed, the results obtained may be misleading and may not reflect the actual body composition.

No differences in the body fat after violating core bioelectrical impedance measurement assumptions

Objective

It is unclear to what degree acutely violating bioelectrical impedance analysis (BIA) measurement assumptions will alter the predicted percent fat mass (%FM) and whether this differs by sex or body mass index (BMI).

Methods

%FM was assessed under control, dehydration, exercise, water, food intake and non-voided bladder conditions with three BIA devices (Tanita: BC-418, TBF-314, & Omron HBF-306CN) for men (n = 23, age: 24.0 ± 5.2 years old) and women (n = 17, age: 22.5 ± 3.4 years old) separately.

Results

For all BIA devices, there were no differences in the %FM values between the control and the other conditions in men or women (− 1.9 to 0.4%, p > 0.05). Across the three devices and five conditions, 97% of %FM tests returned values within 5% of control (2 tests), and 86% of tests were within 2% of control despite violating an assumption. The errors were greatest with dehydration and women were more likely to have a %FM difference greater than 2% than men with dehydration using the hand-to-foot device (Tanita TBF-314: 59% versus 9%). There were no differences in %FM between control and the conditions when examined by BMI (overweight/obesity: − 2.8 to 0.1% and normal weight: − 1.7 to 0.5%; BMI*trial, p = 0.99).

Conclusion

%FM estimates were similar despite acutely violating the preliminary measurement BIA assumptions across a range of different BMIs. The minor variations in %FM are smaller than what would be expected with day-to-day variability or weight loss intervention but may be larger in women than men.

Effects of Water Restriction and Water Replenishment on the Content of Body Water with Bioelectrical Impedance among Young Adults in Baoding, China: A Randomized Controlled Trial (RCT)

Insufficient water intake may affect body composition. The purpose of this research was to explore the effects of water restriction and replenishment on body composition and to evaluate the optimum amount of water that improves body composition. A total of 76 young adults aged 18-23 years old (40 males and 36 females) in Baoding, China, were recruited in this randomized controlled trial, with a 100% completion rate. After fasting overnight for 12 h, at 8:00 a.m. of day 2, a baseline test, including anthropometric indices and collection of urine and blood samples, was explored. Participants were then subjected to water restriction for 24 h, and three meals with ≤75% water content were provided. At 8:00 AM of day 3, the same indices were determined as a dehydration test. Then, participants were randomly assigned into four groups: three water replenishment groups (WR groups 1, 2, and 3 given 1000, 500, and 200 mL of purified water, respectively) and one non-replenishment group (NR group, with no water). After 90 min, the same measurements were performed as a rehydration test. Compared with the baseline test, during the dehydration test, the intracellular water to total body water ratio (ICW/TBW) increased; and extracellular water (ECW), ECW/TBW (extracellular water to total body water ratio), and TBW decreased (all p < 0.05). For males, significant differences were found in ECW, ECW/ICW (extracellular water to intracellular water ratio), ICW/TBW, and ECW/TBW (all p < 0.05); for females, significant reductions were found in ICW, ECW, TBW, ECW/ICW, ICW/TBW, and ECW/TBW (all p < 0.05). Furthermore, significant differences were found in ICW, ECW, ICW/TBW, ECW/TBW, ECW/ICW, TBW, and TBW/BW between males and females during the baseline and dehydration test (all p < 0.05). Comparing the dehydration test with the rehydration test, there were significant interactions between time × volume in ICW and TBW (F = 3.002, p = 0.036; F = 2.907, p = 0.040); in males, these were only found in ICW (F = 3.061, p = 0.040); in females, they were found in ICW and TBW (F = 3.002, p = 0.036; F = 2.907, p = 0.040). The ICW levels in WR groups 1 and 2 were all higher than in the NR group (all p < 0.05); the TBW was higher in WR group 1 than in the NR group (p < 0.05). No significant differences were found between WR groups 1 and 2, either in males or in females (all p > 0.05). In the rehydration test, significant differences in body composition were found between males and females among the four groups (all p < 0.05). Water restriction had adverse effects on body composition, and females were more susceptible to water restriction than males. Water replenishment improved the water content of body composition, alleviating the adverse effects of water restriction on ICW and TBW. After water restriction for 36 h, the optimum volume of water to improve body composition among young male adults was 1000 mL, but this was not the case for females.