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)

Abstract

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.

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)

“…Furthermore, women were more sensitive to water supplementation than men, which was consistent with other studies, with more aspects of body composition changed in women than that of men ( 31 ). A study conducted among 56 male wrestlers has reported that, after drinking a carbohydrate–electrolyte solution, the ECW significantly decreased incrementally from the pre-dehydration test to rehydration test; even after 2 hours of rehydration, the ECW did not return to the baseline level ( 53 ).…”

“…One study investigating the effects of different volumes of water on TBW has revealed that, after 500 mL of water supplementation, an increase in TBW by 0.21 kg was found in men, but not in women ( 67 ). Similarly, another study has shown that participants who consumed 1,000 mL of water had higher TBW than their counterparts who drank nothing ( 31 ). The intervals used for measuring the changes in the TBW, as well as the types of fluids supplied to the participants, could explain the differences in the abovementioned studies.…”

“…Studies have shown that total drinking fluids are associated with TBW, confirming the relationship between hydration status and body composition and that TBW/BW decreases with increasing dehydration among children ( 26 – 28 ). In addition, the impairments due to dehydration or water restriction on body composition have been evaluated clearly in studies conducted among people or animals ( 29 – 31 ). To our knowledge, only a few studies have analyzed the correlation between the body composition and water supplementation, in which the researchers did not obtain similar results ( 32 , 33 ).…”

Assessment of Hydration Status and Blood Pressure in a Tertiary Care Hospital at Al-Khobar

“…Although there are multiple techniques for the measurement of body fluid compartments, bioimpedance spectroscopy (BIS) remains a reliable, costeffective technology that identifies body composition by sending electrical waves and estimating resistance values from very high to very low resistance numbers [5]. In addition, BIS allows measuring water compartments separately (total body water (TBW), ECW, and ICW) [5,6].…”

Total body water and sicca symptoms in primary Sjögren's syndrome

“…Determining the body liquid volume has been useful in some diseases such as renal disorders and heart failure (7,8). Moreover, the ratio between extracellular and intracellular fluid has been proposed as an index of health status (9). Nevertheless, TBW has not been previously evaluated in patients with PSS who suffer from impaired production of tears and saliva, both of them as previously mentioned constituted by a high percentage of water.…”