Bioelectrical impedance analysis does not detect an increase in total body water following isotonic fluid consumption

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].

Utility of an Isotonic Beverage on Hydration Status and Cardiovascular Alterations

This study determined the beverage hydration index (BHI) and postprandial cardiac autonomic activity after consuming an isotonic beverage (IB) compared to distilled water (DW). Twenty-two participants (50% female; mean ± SD; age, 27 ± 3 year; height, 169.1 ± 12.6 cm; weight, 73.3 ± 13.8 kg; BF%, 23 ± 10%) completed two experimental trials where they consumed 1 L DW or an IB; after which urine volume and cardiac autonomic activity was measured through 240 min. Cardiac autonomic activity was quantified using heart rate (HR), log transformed heart rate variability measures (root mean square of successive R–R intervals; RMSSD; low frequency, LF; and high frequency, HF) and systolic time intervals (pre-ejection period, PEP). BHI was significantly greater after IB consumption at min 0 (MD [95% CI]; 1.31 [0.35, 2.27]), 180 min (0.09 [0.022, 0.16]), and 240 min (0.1 [0.03, 0.17]) compared to DW (p = 0.031). Net fluid balance was significantly greater in IB than DW at 180 min (90 [−16.80, 196.81]) and 240 min (106 [−13.88, 225.88]) (p = 0.037). HR decreased over time in both beverage trials but was higher following IB ingestion at 0 min (3.9 [−2.42, 10.22]), 30 min (5.3 [−0.94, 11.54]), and 60 min (2.7 [−3.42, 8.82]) (p = 0.0002). lnHF was greater 30 min post DW ingestion compared to IB (0.45 [−0.23, 1.13]) (p = 0.039). IB promotes greater fluid retention capacity compared to DW within 4 hours of consumption. The variations in cardiac autonomic measures may warrant further investigation in clinical populations (i.e., patients with autonomic failure).

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.

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

Body composition analysis may provide valuable information about the assessment of balance between fluid, fat, and fat-free mass. The present study assessed whether the regular increase in water consumption has any significant effects on measurements of body composition using BIA. A total of 140 subjects participated in this study. Body composition analyses of the subjects were performed for five times using foot to foot BIA; first at baseline and four times, after 15 minutes of each 500 mL water intakes. There was overestimation in body fat mass compared to the baseline and increased significantly after water intakes in males (2.08% in 500 mL, 3.80% in 1000 mL, 5.88% in 1500 mL, and 7.92% in 2000 mL, p < 0.05) and in females (3.4% in 500 mL, 5.7% in 1000 mL, 7.8% in 1500 mL, and 9.4% in 2000 mL, p < 0.05). In contrast, there was markedly underestimation of total body water and fat-free mass in males (35% and 50%) and females (17% and 22%), respectively, at the end of the study. Thus, overestimation of body fat mass and lower estimation of total body water and fat-free mass with closely to the amount of water retention using BIA application should be considered in health-related clinical practice.

Classification Accuracy of Body Mass Index for Excessive Body Fatness in Kuwaiti Adolescent Girls and Young Adult Women

PURPOSE

Adolescent obesity, as defined by BMI, is amongst the highest in the world in Kuwait. This study aimed to determine the extent to which BMI might be underestimating obesity as defined by excessive fatness in Kuwaiti female adolescents and young adults.

METHODS

A total of 400 apparently healthy Kuwaiti female university students (mean age 18.0 years, SD 0.6) were recruited. Excessive fatness was defined as body fat percentage ≥30, measured using the Tanita model TBF-310 Bio-impedance system with the manufacturer's equation. Obesity was defined as recommended by the WHO in adult participants - those aged ≥19.1 years - as BMI≥30 kg/m². In the adolescent participants (age <19.1 years) obesity was defined as recommended by the WHO as a BMI-for-age Z score of ≥2.00. The accuracy of BMI-defined obesity to identify excessively fat individuals was determined by estimating the prevalence of obesity using high BMI and prevalence of excessive fatness, and by calculating sensitivity and specificity and predictive values.

RESULTS

Median BMI was 27.8 kg/m² (range 15.1-51.2) and median body fat percentage was 32.0 (range 5.0-54.0). The prevalence of excessive fatness was 62% (247/400 individuals were excessively fat), while the prevalence of obesity according to BMI was 42% (169/400 individuals were obese according to their BMI). The sensitivity of BMI to identify the excessively fat individuals was moderate (66%) but specificity was high (96%). The positive predictive value of BMI was 96% and the negative predictive value was 64%.

CONCLUSION

BMI-based measures substantially underestimate the prevalence of excessive fatness in Kuwaiti adolescent females. Obesity is even more prevalent, and requires more urgent attention, than is apparent from BMI-based measures used in most research and national surveys. BMI may also be too crude for use as an exposure or outcome variable in many epidemiological studies of Arab adolescent girls and adult women.

Bioelectrical Impedance Analysis Is Not Sufficient for Determining Water Deficit in Hypernatremic Patients

BACKGROUND Hypernatremia is associated with poor outcomes in critically ill patients, and an accurate assessment of water volume is important to determine appropriate fluid hydration. Bioelectrical impedance analysis (BIA) is a new, noninvasive, and relatively easy method for measuring hydration status. This study aimed to investigate whether bioelectrical impedance measurements of body water could reduce the frequency of blood sampling for fluid replacement in patients with hypernatremia. MATERIAL AND METHODS Fifty-one hospitalized patients were studied with hypernatremia, defined as a serum sodium ≥150 mmol/L determined by laboratory testing. Laboratory and BIA measurements were compared, and water deficiency was calculated with a conventional formula (sodium-corrected Watson formula) and measured by BIA. RESULTS The value of the absolute fluid overload (AFO) equivalent to the overhydration (OH) value, determined using BIA, did not accurately represent water deficit in patients with hypernatremia (r=0.137, P=0.347). Although the total body water (TBW) measured by BIA showed a significant correlation with that determined by the conventional formula (r=0.861, P<0.001), there was a proportional bias (r=0.617, P<0.001). The intracellular water (ICW) measured by BIA underestimated the TBW level calculated by the conventional formula by about 14.06±4.0 L in the Bland-Altman analysis. CONCLUSIONS It is not currently possible to replace blood testing with BIA for assessing volume status in hypernatremic patients. However, ICW value measured by BIA might represent plasma sodium level more accurately than extracellular water (ECW) or TBW value in patients with hypernatremia.