Body Water Turnover Research Articles

High starch intake favours body weight control in neutered and spayed cats living in homes fed ad libitum.

Different starch-to-protein ratios were compared among neutered and spayed domiciled cats. Male and female obese and non-obese cats were fed kibble diets ad libitum for 4 months high in starch (HS (38 % crude protein (CP)): starch 32 %, protein 38 %; DM basis) or high in protein (HP (55 % CP): starch 19 %, protein 55 %) but similar in energy and fat in a crossover design. Physical activity was evaluated using an accelerometer, and body composition (BC), energy expenditure (EE) and water turnover (WT) using the doubly labelled water method. Results were compared in a 2 diet × 2 sex × 2 body condition factorial arrangement. Cats fed the HS (38 % CP) diet maintained a constant body weight, but lean mass (LM) tended to be reduced in female obese but to be increased in male non-obese (P < 0·08) and increased in female non-obese cats (P = 0·01). The HP (55 % CP) diet induced an increase in cat body weight and LM (P < 0·05) without altering BC proportion. EE tended to be higher in males (351 (se 8) kJ/kg0·67/d) than females (330 (se 8) kJ/kg0·67/d; P = 0·06), was unaffected by diet or BC, decreased as age increased (R 2 0·44; P < 0·01) and increased as physical activity increased (R 2 0·58; P < 0·01). WT was higher for the HP (55 % CP) diet (P < 0·01) and increased with EE (R 2 0·65; P < 0·01). The HS (38 % CP) diet favoured body weight control during 4 months of ad libitum feeding. Caution is necessary to balance protein in diets of female obese cats over 5 years, as they may have low energy and food intake, with LM loss.

Hydration Status in Older Adults: Current Knowledge and Future Challenges.

Adequate hydration is essential for the maintenance of health and physiological functions in humans. However, many older adults do not maintain adequate hydration, which is under-recognized and poorly managed. Older adults are more vulnerable to dehydration, especially those living with multiple chronic diseases. Dehydration is associated with adverse health outcomes in older adults, and acts as an independent factor of the hospital length of stay, readmission, intensive care, in-hospital mortality, and poor prognosis. Dehydration is a prevalent health problem in older adults, accounting for substantial economic and social burden. This review attempts to provide current knowledge of hydration including patterns of body water turnover, the complex mechanisms behind water homeostasis, the effects of dehydration on the health of the body, and practical guidance for low-intake dehydration in older adults.

Sex And Habitual Water Intake Are Related To Dimensions Of Mood

Water intake has previously been linked to dimensions of mood and other cognitive performance. However, it is yet to be determined if the relationships are solely because of changes in water intake (i.e., moving from high to low-volume consumption) or if they can be linked to habitual intake. Furthermore, sex differences related to the effect of water on mood have yet to be outlined. PURPOSE: To assess for differences in mood-dimensions across fluid volume demarcations and biological sex using objective measures of habitual water intake. METHODS: 51 women (42 ± 14y, 164 ± 6 cm, 72.0 ± 16.6 kg) and 49 men (40 ± 13 y, 177 ± 7 cm, 81.5 ± 16.0 kg) took part in the current study over 8 days. Participants consumed 0.05 g⸱kgLBM-1 of deuterium oxide (2H2O) at baseline. Then, 2H2O urine enrichment was measured 1 and 7 days after to determine total body water turnover (WTO) by dilution method. Participants simultaneously completed food diaries which were used to calculate metabolic water production given participant weight stability. Total water intake (TWI) was calculated as WTO-metabolic water production. The profile of mood state survey (POMS) and a visual analog scale to measure alertness were completed on the second day of observation. Data were dichotomized by sex and divided into HIGH (4.5 ± 1.4, 4.7 ± 1.1 L⸱d-1), MOD (2.9 ± 0.2, 3.3 ± 0.2 L⸱d-1), and LOW (2.2 ± 0.2, 2.7 ± 0.3 L⸱d-1) TWI tertiles, for women and men, respectively. RESULTS: Alertness and Vigor were significantly greater within women in HIGH versus MOD and LOW (all P ≤ 0.027), while Depression was lower in HIGH compared to LOW (P = 0.015). There were no significant differences in any mood-dimensions between any male TWI groups (all P ≥ 0.124). After controlling for macronutrient intake and physical activity, follow-up regression modeling in women, identified that the addition of TWI produced a significant change in the F score of the models for Depression, Anxiety, Vigor, and Total Mood Disturbance (all P ≤ 0.043). CONCLUSION: Within this sample, increased habitual water consumption was related to more favorable dimensions of mood in women, but not men. The conflicting results between sexes may be because of a larger TWI range in women relative to lean body mass and/or differences in fluid handling as evidenced by prior reporting on the divergence of urine concentrations between sexes.

A simple CO2 equilibration method for measuring blood oxygen isotope compositions.

Blood water oxygen isotope compositions can provide valuable insights into physiological processes and ecological patterns. While blood samples are commonly drawn for medical or scientific purposes, blood fractions are infrequently measured for oxygen isotopic compositions (δ18 O) because such measurements are time consuming and expensive. We sampled blood from sheep, goats, and iguanas raised in field and animal laboratories into serum, EDTA, heparin, and uncoated plastic vials commonly used in medical and scientific research, then separated red blood cell (RBC) and plasma or serum blood fractions. These were injected into helium-flushed Exetainer tubes where they naturally outgassed endogenous CO2 (goat blood), or into He- and CO2 -flushed tubes (iguana blood). The CO2 gas was sampled on a GasBench II system, and δ18 O was measured by an isotope ratio mass spectrometer (IRMS). Repeated δ18 O measurements were stable over multiple days. The addition of desiccated blood solids to water standards had little impact on their δ18 O measurements, suggesting that organic molecular constituents within blood serum and plasma do not interfere with blood water δ18 O values. We observed slight but statistically significant δ18 O offsets between plasma, serum and RBC fractions. Mass-dependent body water turnover times for iguanas were derived from the data. We demonstrate that a simple blood-CO2 equilibration method using the GasBench can quickly, reliably and accurately characterize water δ18 O in the plasma, RBC, and whole blood fractions of mammalian and reptilian blood samples (precision ≤ 0.1‰). This method will expand the application of blood stable isotope analysis in physiological and medical research.

Contribution of Dietary Composition on Water Turnover Rates in Active and Sedentary Men

Body water turnover is a marker of hydration status for measuring total fluid gains and losses over a 24-h period. It can be particularly useful in predicting (and hence, managing) fluid loss in individuals to prevent potential physical, physiological and cognitive declines associated with hypohydration. There is currently limited research investigating the interrelationship of fluid balance, dietary intake and activity level when considering body water turnover. Therefore, this study investigates whether dietary composition and energy expenditure influences body water turnover. In our methodology, thirty-eight males (19 sedentary and 19 physically active) had their total body water and water turnover measured via the isotopic tracer deuterium oxide. Simultaneous tracking of dietary intake (food and fluid) is carried out via dietary recall, and energy expenditure is estimated via accelerometery. Our results show that active participants display a higher energy expenditure, water intake, carbohydrate intake and fibre intake; however, there is no difference in sodium or alcohol intake between the two groups. Relative water turnover in the active group is significantly greater than the sedentary group (Mean Difference (MD) [95% CI] = 17.55 g·kg−1·day−1 [10.90, 24.19]; p = < 0.001; g[95% CI] = 1.70 [0.98, 2.48]). A penalised linear regression provides evidence that the fibre intake (p = 0.033), water intake (p = 0.008), and activity level (p = 0.063) predict participants’ relative body water turnover (R2 = 0.585). In conclusion, water turnover is faster in individuals undertaking regular exercise than in their sedentary counterparts, and is, in part, explained by the intake of water from fluid and high-moisture content foods. The nutrient analysis of the participant diets indicates that increased dietary fibre intake is also positively associated with water turnover rates. The water loss between groups also contributes to the differences observed in water turnover; this is partly related to differences in sweat output during increased energy expenditure from physical activity.

Combining Models of Environment, Behavior, and Physiology to Predict Tissue Hydrogen and Oxygen Isotope Variance Among Individual Terrestrial Animals

Variations in stable hydrogen and oxygen isotope ratios in terrestrial animal tissues are used to reconstruct origin and movement. An underlying assumption of these applications is that tissues grown at the same site share a similar isotopic signal, representative of the location of their origin. However, large variations in tissue isotopic compositions often exist even among conspecific individuals within local populations, which complicates origin and migration inferences. Field-data and correlation analyses have provided hints about the underlying mechanisms of within-site among-individual isotopic variance, but a theory explaining the causes and magnitude of such variance has not been established. Here we develop a mechanistic modeling framework that provides explicit predictions of the magnitude, patterns, and drivers of isotopic variation among individuals living in a common but environmentally heterogeneous habitat. The model toolbox includes isoscape models of environmental isotopic variability, an agent-based model of behavior and movement, and a physiology-biochemistry model of isotopic incorporation into tissues. We compare model predictions against observed variation in hatch-year individuals of the songbird Spotted Towhee (Pipilo maculatus) in Red Butte Canyon, Utah, and evaluate the ability of the model to reproduce this variation under different sets of assumptions. Only models that account for environmental isotopic variability predict a similar magnitude of isotopic variation as observed. Within the modeling framework, behavioral rules and properties govern how animals nesting in different locations acquire resources from different habitats, and birds nesting in or near riparian habitat preferentially access isotopically lighter resources than those associated with the meadow and slope habitats, which results in more negative body water and tissue isotope values. Riparian nesters also have faster body water turnover and acquire more water from drinking (vs. from food), which exerts a secondary influence on their isotope ratios. Thus, the model predicts that local among-individual isotopic variance is linked first to isotopic heterogeneity in the local habitat, and second to how animals sample this habitat during foraging. Model predictions provide insight into the fundamental mechanisms of small-scale isotopic variance and can be used to predict the utility of isotope-based methods for specific groups or environments in ecological and forensic research.

Air temperature and diet influence body composition and water turnover in zoo-living African elephants (Loxodonta africana).

African elephants, the largest land animal, face particular physiological challenges in captivity and the wild. Captive elephants can become over- or under-conditioned with inadequate exercise and diet management. Few studies have quantified body composition or water turnover in elephants, and none to date have examined longitudinal responses to changes in diet or air temperature. Using the stable isotope deuterium oxide (2H2O), we investigated changes in body mass, estimated fat-free mass (FFM, including fat-free gut content) and body fat in response to a multi-year intervention that reduced dietary energy density for adult African elephants housed at the North Carolina Zoo. We also examined the relationship between air temperature and water turnover. Deuterium dilution and depletion rates were assayed via blood samples and used to calculate body composition and water turnover in two male and three female African elephants at six intervals over a 3-year period. Within the first year after the dietary intervention, there was an increase in overall body mass, a reduction in body fat percentage and an increase in FFM. However, final values of both body fat percentage and FFM were similar to initial values. Water turnover (males: 359 ± 9 l d−1; females: 241 ± 28 l d−1) was consistent with the allometric scaling of water use in other terrestrial mammals. Water turnover increased with outdoor air temperature. Our study highlights the physiological water dependence of elephants and shows that individuals have to drink every 2–3 days to avoid critical water loss of approximately 10% body mass in hot conditions.

Validation and Reliability of a Water Frequency Questionnaire to Estimate Daily Water Intake in Adults (P13-006-19)

ObjectivesInvestigators sought to: 1) evaluate the validity of a water frequency questionnaire (WFQ) to estimate mean daily water intake (WI) in adults through comparison to the gold standard, deuterium oxide (D2O) disappearance, and 2) evaluate reliability of WFQ to estimate WI. MethodsData collection occurred over three weeks, with validity of WFQ (vs. D2O) assessed during week one (W1) and reliability assessed between W1 and week three (W3). Healthy, free-living adults (n = 103; 51% female; 41 ± 14 y; BMI, 26.5 ± 5.5 kg·m–2) consumed D2O (0.1 g·kg–1 lean mass) at the start of W1 and provided urine samples immediately before ingestion, the following day, and at the end of the week to calculate total body water turnover (WTO). Seven day beverage consumption during W1 and W3 was retrospectively estimated using the WFQ. The WFQ included 17 beverage types with specified volumes (e.g., water (8 oz); soft drink (12 oz)) and nine frequency options ranging from ‘Never or less than 1 per week’ to ‘7+ per day’. Investigators converted beverage volumes to mL and calculated WI for each week. Food frequency questionnaires were also completed at the end of both weeks. Diets were analyzed with Nutritional Data System for Research software to estimate water intake from solid foods and metabolic water production by macronutrient oxidation. Water from food and macronutrient oxidation were subtracted from WTO to estimate WI via D2O. WFQ reliability was assessed via intraclass correlation (ICC) and Cronbach α, and validity was assessed via Bland-Altman plots. ResultsThe mean difference in WI between D2O (2902 ± 1321 mL·day–1) and WFQ (2589 ± 1560 mL·day–1) was –308 ± 166 mL (P = 0.065). No systematic bias was observed between methods (R2 = 0.032, P = 0.071) as 3% of WI variance was explained by differences between methods. WFQ WI was not different between W1 (2589 ± 1560 mL·day–1) and W3 (2441 ± 1334 mL·day–1, P = 0.135). Cronbach α = 0.8415 demonstrated high internal consistency in WI estimation. The ICC was 0.834 (95% CI: 0.754, 0.887), demonstrating good test-retest reliability of WFQ. ConclusionsIn conclusion, the WFQ produced reliable WI estimates that were comparable to the gold standard of D2O assessment. This questionnaire may be a practical and easy method for assessing water intake in adults. Funding SourcesThe study was funded by Danone Research.

A user-friendly calculator for determining oxygen isotope composition of body water in cows based on the MK model and examples of its applications

Oxygen isotope composition (δ18O) of body water or protein shows potential for tracing production systems in animal products like milk. However, parameters influencing this value are difficult to investigate by controlled experiments due to fluctuating ambient conditions and due to the slow body water turnover that requires large amounts of isotopically constant diet (e.g. drinking water and feed moisture) to achieve equilibrium conditions. A mechanistic model (MK model) was developed as a promising assistant to predict environmental, physiological and animal management related influences on δ18O of body water. A user-friendly spreadsheet calculator (MK calculator) allows running this model. Measured data of milk and hair were used for validation and showed a root mean squared error of 1.3‰ (n = 796) and a Nash-Sutcliffe modeling efficiency of 95%. Examples of application are divers like (1) evaluating the interaction of ambient conditions with feeding strategies; (2) looking into influences of fraction of grass silage and its δ18O on δ18O of body water; (3) investigating the influence of moisture contents in grass, grass silage and hay; (4) predicting the influence of drinking water on δ18O of body water depending on feeding strategy; (5) assessing the half-life of body water depending on physiological state and ambient conditions. The MK calculator may be applied for a wide range of questions related to δ18O of body water like influences of animal behavior, of diseases, or of transhumance. The MK calculator is also easy to adapt to other animals than cows.

Hydration measured by doubly labeled water in ALS and its effects on survival

We present a study of hydration in ALS patients and its effects on survival. This was a multicenter study over 48 weeks in 80 ALS patients who underwent 250 individual measurements using doubly labeled water (DLW). Total body water (TBW) and water turnover (a surrogate for water intake) were 3.4% and 8.6% lower, respectively, in patients compared to age- and gender-matched healthy controls, and both significantly decreased over study duration. In 20% of patients, water turnover measured over 10 d was 2 standard deviations below the mean value in healthy controls. In a separate clinic cohort of 208 patients, water intake estimated from a de novo equation created from common clinical endpoints was a prognostic indicator of survival. Regardless of nutritional state assessed by BMI, survival was two-fold longer in the group above the median for estimated water intake, suggesting that hydration may be a more important predictor of survival than malnutrition. Risk factors for poor hydration were identified. Water intake equations recommended by US Centers for Medicare and Medicaid Services in healthy elderly were inaccurate for use in ALS patients. We developed equations to estimate TBW and water intake in ALS patients for use in clinics to accurately estimate hydration and improve clinical care.

Validation Testing Demonstrates Efficacy of a 7-Day Fluid Record to Estimate Daily Water Intake in Adult Men and Women When Compared with Total Body Water Turnover Measurement

Background: Mean daily water intake from fluids (WATER-FL) has proven to be difficult to measure because of a range of nonvalidated data collection techniques. Few questionnaires have been validated to estimate WATER-FL against self-reported diaries or urinary hydration markers, which may limit their objectivity.Objectives: The goals of this investigation were 1) to assess the validity of a 7-d fluid record (7dFLR) to measure WATER-FL (WATER-FL-7dFLR) through comparison with WATER-FL as calculated by measuring deuterium oxide (D2O) disappearance (WATER-FL-D2O), and 2) to evaluate the reliability of the 7dFLR in measuring WATER-FL.Methods: Participants [n = 96; 51% female; mean ± SD age: 41 ± 14 y; mean ± SD body mass index (in kg/m2): 26.2 ± 5.1] completed body water turnover analysis over 3 consecutive weeks. They completed the 7dFLR and food diaries during weeks 2 and 4 of the observation. The records were entered into nutritional software to determine the water content of all foods and fluids consumed. WATER-FL-D2O was calculated from water turnover (via the D2O dilution method), minus water from food and metabolic water. The agreement between the 2 methods of determining WATER-FL were compared according to a Bland-Altman plot at week 2. The test-retest reliability of 7dFLR between weeks 2 and 4 was assessed via intraclass correlation (ICC).Results: The mean ± SD difference between WATER-FL-7dFLR and WATER-FL-D2O was -131 ± 845 mL/d. In addition, no bias was observed (F[1,94] = 0.484; R2 = 0.006; P = 0.488). When comparing WATER-FL-7dFLR from weeks 2 and 4, no significant difference (mean ± SD difference: 71 ± 75 mL/d; t[79] = 0.954; P = 0.343) and an ICC of 0.85 (95% CI: 0.77, 0.90) was observed.Conclusions: The main findings of this study were that the use of the 7dFLR is an effective and reliable method to estimate WATER-FL in adults. This style of questionnaire may be extremely helpful for collecting water intake data for large-scale epidemiologic studies.

Use of water turnover method to measure mother's milk flow in a rat model: Application to dams receiving a low protein diet during gestation and lactation.

Assessment of milk production is of utmost relevance for pediatricians and scientists interested in early life nutrition. The weight-suckle-weight (WSW) method, which consists of weighing babies before and after they suckle their mother, uses the difference in body weight as an estimate of milk intake. However, this is prone to many sources of error. In the current study, we used for the first time the water turnover method and compartmental analysis with deuterated water (D2O) as a non-toxic tracer to quantify in vivo milk production in a rat model. We assessed the effect of a nutritional intervention presumed to affect milk production, a maternal dietary protein restriction during gestation and lactation, which results in the birth of pups with intrauterine growth restriction. The specific aim of this study was to determine milk production with the body water turnover method in rat dams receiving during gestation and lactation, either a control diet (NP) or an iso-caloric low-protein diet (LP). In NP dams, mass of dam’s total body water, output flow constant from dam to litter (K21) and median milk flow, calculated between days 11 to 14 after pup birth, were 282.1 g, 0.0122 h-1 and 3.30 g/h for NP dams, respectively. Maternal dietary protein restriction (-59%) during perinatal period led to a 34% reduction in milk flow (NP versus LP). With the WSW method, milk flow varied from 1.96 g/h to 2.37 g/h between days 11 to 14 for NP dams. The main advantage of the D20 method compared to the WSW method stems from its higher precision, as attested by the narrowest range of measured values of milk flow ([2.90; 3.75] and [0.98; 6.85] g/h, respectively) for NP group. This method could be suitable for testing the effectiveness of candidate galactologue molecules presumed to enhance milk production in the lactating rat model.

Water Turnover, Urinary Markers Of Hydration, And Mood In Men And Women

PURPOSE: Past research has identified relationships between daily total water intake (TWI) measured by diet diary with dimensions of mood in free living, and laboratory confined men and women. However, diet records have been associated with subjective errors and thus these findings should be confirmed in objective of body water turnover (WTO). METHODS: 49 women (42±14y, 164±6cm, 71±16kg) and 46 men (40±14y, 177±7cm, 81±16kg) volunteered for WTO measurement via deuterium oxide dilution technique over two consecutive weeks. Total water intake (TWI) was calculated as WTO (L·d-1) - metabolic water production. The Profile of Mood State questionnaire (POMS) was administered in the morning on the 4th day of each week. Physical activity was assessed with the International Physical Activity Questionnaire. The influence of the prior days, and acute hydration status (via urine osmolality) on mood was considered with; a) 24h urine collections comprised of the full day leading up to, and, b) single urine samples collected immediately prior to completion of the POMS. Measurements were averaged between weeks. Multivariate linear regression was completed to assess if WTO or either of the hydration markers predicted any of the 6 POMS sub-scales or the composite mood measurement of total mood disturbance, over and above the influence of age, body mass index, and MET minutes of physical activity completed during the week. RESULTS: The vigor sub-scale of was significantly associated with WTO, (Fchange[1,94]=5.00, R2change=0.05, Beta=0.23, P=0.03). This finding was not apparent in relationships with 24h urine osmolality (Fchange[1,94]=2.58, R2change=0.03, Beta=0.16, P=0.11) or single sample urine osmolality (Fchange[1,94]=2.65, R2change=0.03, Beta=-0.17, P=0.10). No other sub-scales or TMD were significantly related to WTO, or hydration indices, after accounting for the covariates. CONCLUSIONS: This study confirms a positive relationship between mood and fluid intake using direct measurement of WTO. The lack of significance to urinary hydration markers is indicative of the multi-faceted composition of urine concentration (i.e., kcal, protein intake, etc.). However, daily WTO is modestly associated with mood and should be further explored in controlled laboratory conditions to further elucidate this relationship.

The Integration of Gastrointestinal and Renal Function in Nectar‐Feeding Birds

Nectar‐feeding birds face a constant challenge in terms of water balance, experiencing water loading when feeding and potential dehydration when fasting. A growing collection of studies is revealing how species across different orders deal with this osmoregulatory challenge. To meet their high mass‐specific energy demands these birds must often deal with exceptionally high proportionate water fluxes. Birds that ingest large volumes of water may either eliminate excess water in the kidney or regulate the volume of water absorbed in the gastrointestinal tract. Across species, renal filtration during feeding periods generally does not exceed allometric predictions and is not highly responsive to water loading, but renal fractional water reabsorption varies with water load as expected. Hummingbirds (Apodiformes) absorb a constant, high proportion of ingested water across the gastrointestinal tract, while sunbirds and honeyeaters (Passeriformes) modulate intestinal water absorption, potentially avoiding significant water loads when feeding on dilute diets. Data suggest that these passerine nectarivores regulate transepithelial water flux independently of sugar absorption, opening the door to intriguing questions about how water transport is regulated in the vertebrate gastrointestinal tract. Despite reducing their intestinal water absorption, these birds show linear increases in water flux and fractional body water turnover as water intake increases, suggesting that the modulation of fractional water absorption is not sufficient to completely offset dietary water loads. Species in both orders exhibit significant diel variation in renal filtration, essentially shutting down renal filtration during overnight fasts and thus avoiding dehydration. Convergence in diet has led to the evolution of many similar traits in hummingbirds and sunbirds, but the physiological traits of these two groups that allow the processing of a watery and sugary diet may be very different.

Hydrogen and oxygen stable isotope fractionation in body fluid compartments of dairy cattle according to season, farm, breed, and reproductive stage.

Environmental temperature affects water turnover and isotope fractionation by causing water evaporation from the body in mammals. This may lead to rearrangement of the water stable isotope equilibrium in body fluids. We propose an approach to detect possible variations in the isotope ratio in different body fluids on the basis of different homoeothermic adaptations in varying reproductive stages. Three different reproductive stages (pregnant heifer, primiparous lactating cow, and pluriparous lactating cow) of two dairy cattle breeds (Italian Friesian and Modenese) were studied in winter and summer. Blood plasma, urine, faecal water, and milk were sampled and the isotope ratios of H (2H/1H) and O (18O/16O) were determined. Deuterium excess and isotope-fractionation factors were calculated for each passage from plasma to faeces, urine and milk. The effects of the season, reproductive stages and breed on δ 2H and δ 18O were significant in all the fluids, with few exceptions. Deuterium excess was affected by season in all the analysed fluids. The correlations between water isotope measurements in bovine body fluids ranged between 0.6936 (urine-milk) and 0.7848 (urine-plasma) for δ 2H, and between 0.8705 (urine-milk) and 0.9602 (plasma-milk) for δ 18O. The increase in both isotopic δ values in all body fluids during summer is representative of a condition in which fractionation took place as a consequence of a different ratio between ingested and excreted water, which leads to an increased presence of the heavy isotopes. The different body water turnover between adult lactating cattle and non-lactating heifers was confirmed by the higher isotopic δ for the latter, with a shift in the isotopic equilibrium towards values more distant from those of drinking water.

Body composition, water turnover and physical activity among women in Narok County, Kenya.

BackgroundIn developing countries where access to water and food is not guaranteed, women may have to travel long distances or engage in intense physical activities to gather food. This may compromise their water requirements and overall nutritional status. The aim of the study was to determine water turnover, physical activity and body composition among women in Kenya and to describe the differences between rural and urban Kenyan women.MethodsThirty women from Narok County who were not pregnant at the time of the study were recruited. Body mass index (BMI) was calculated by dividing weight in kilograms by height in meters squared. Deuterium dilution was used to determine total body water (TBW) and water turnover was measured from deuterium elimination. Fat-free mass (FFM) was calculated by assuming a constant hydration fraction of 73.2%. Accelerometers (Actigraph GT3X) were used to assess physical activity and expressed as Vector magnitude counts per day (VM/day). Simple and multiple linear regressions were used to define the determinants of water turnover.ResultsMean BMI was 23.4 ± 4.1 and 21.5 ± 3.8 among rural and urban women respectively. The prevalence of overweight (BMI > 25 kg/m2) was 24.1% and of underweight (BMI < 18.4 kg/m2) was 25%. The mean total body water (TBW) was 29.3 ± 4.2 liters (L) and water turnover was 3.2 ± 0.8 liters per day (L/day). Water loss was positively associated with BMI (R2 = .45, p < 0.001, n = 28) and Fat mass index (FMI) (R2 = .41, p < 0.001, n = 28). Water loss was also positively associated with physical activity (PA) (R2 = .25, p < 0.05, n = 22). Multiple regression analysis showed that physical activity in addition to BMI in the model explained an additional 15% of the variation in water turnover (r2 = 0.53, p < 0.05; ∆r2 = 0.15, p < 0.05, n = 22) compared to BMI alone (r2 = 0.38, p < 0.005 n = 22).ConclusionBMI together with physical activity were the strongest predictors of water loss.

Total body water and water turnover rates in the estuarine diamondback terrapin (Malaclemys terrapin) during the transition from dormancy to activity.

Water and salt concentrations in an animal's body fluids can fluctuate with changing environmental conditions, posing osmoregulatory challenges that require behavioral and physiological adjustments. The purpose of this study was to investigate body water dynamics in the estuarine diamondback terrapin (Malaclemys terrapin), a species that undergoes seasonal dormancy in salt marsh habitats. We conducted a field study to determine the total body water (%TBW), water turnover rate (WTR) and daily water flux (DWF) of female terrapins in south eastern North Carolina pre- and post-emergence from winter dormancy. Terrapins were injected with [(2)H]deuterium on two occasions and washout of the isotope was monitored by taking successive blood samples during the period of transition from dormancy to activity. The WTR and DWF of dormant terrapins were significantly lower than those of active terrapins (WTR(dormant)=49.70±15.94 ml day(-1), WTR(active)=100.20±20.36 ml day(-1), DWF(dormant)=10.52±2.92%TBW day(-1), DWF(active)=21.84±7.30%TBW day(-1)). There was no significant difference in %TBW between dormant and active terrapins (75.05±6.19% and 74.54±4.36%, respectively). The results from this field study provide insight into the terrapin's ability to maintain osmotic homeostasis while experiencing shifts in behavioral and environmental conditions.

Gastrointestinal and renal responses to variable water intake in whitebellied sunbirds and New Holland honeyeaters

Nectarivores face a constant challenge in terms of water balance, experiencing water loading or dehydration when switching between food plants or between feeding and fasting. To understand how whitebellied sunbirds and New Holland honeyeaters meet the challenges of varying preformed water load, we used the elimination of intramuscular-injected [(14)C]-l-glucose and (3)H2O to quantify intestinal and renal water handling on diets varying in sugar concentration. Both sunbirds and honeyeaters showed significant modulation of intestinal water absorption, allowing excess water to be shunted through the intestine when on dilute diets. Despite reducing their fractional water absorption, both species showed linear increases in water flux and fractional body water turnover as water intake increased (both afternoon and morning), suggesting that the modulation of fractional water absorption was not sufficient to completely offset dietary water loads. In both species, glomerular filtration rate was independent of water gain (but was higher for the afternoon), as was renal fractional water reabsorption (measured in the afternoon). During the natural overnight fast, both sunbirds and honeyeaters arrested whole kidney function. Evaporative water loss in sunbirds was variable but correlated with water gain. Both sunbirds and honeyeaters appear to modulate intestinal water absorption as an important component of water regulation to help deal with massive preformed water loads. Shutting down glomerular filtration rate during the overnight fast is another way of saving energy for osmoregulatory function. Birds maintain osmotic balance on diets varying markedly in preformed water load by varying both intestinal water absorption and excretion through the intestine and kidneys.

Energy expenditure and water turnover in hunting dogs in winter conditions

Hunting with dogs in winter conditions is practised in the Nordic countries. The present study aimed at determining daily energy expenditure (DEE) and body water turnover (BWT) by the doubly labelled water technique in eight hunting dogs (body-weight (BW) range 14-27 kg) working 3 h/d for 3 d (-6 °C) on ground covered with 20-40 cm of loose snow, to provide information on energy and water requirements. The mean distance run during the hunting period was recorded by the global positioning system and averaged 19.4 km/d. DEE increased with increasing BW (P < 0.001) and varied between 7.20 and 16.6 MJ/d (mean 11.0 MJ/d) corresponding to 950-1350 kJ/kg BW(0.75) per d (mean 1170 kJ/kg BW(0.75) per d). The larger dogs tended to run longer than the smaller dogs and therefore spent more energy per kg BW(0.75) but not significantly (P>0.05). DEE values determined were close to the values measured for hunting dogs running for 3 h/d in hot climates, suggesting that climate within the range of the two studies has little impact on energy expenditure per h running activity. Compared with the work of sled dogs per km travelled running on a track, the work performed by the hunting dogs was suggested to be higher when running in a loose snow layer. However, DEE was much lower because sled dogs ran for a longer distance each day. Mean BWT was 217 ml/kg BW(0.75) or 19 ml/kJ metabolisable energy.

Seasonal body composition, water turnover, and field metabolic rates in porcupines (Erethizon dorsatum) in Alaska

Abstract Winter extremes of temperature and food shortage limit the distribution of arctic animals. North American porcupines (Erethizon dorsatum) are one of the most widely distributed mammals in North America and range from deserts to arctic tundra. In Alaska porcupines remain active at low winter temperatures (i.e., −39°C) while consuming woody plants that are low in nitrogen (N) and high in both fiber and plant secondary metabolites. Porcupines conserved lean body mass in winter by using fat stores. Fat mass declined from 50% ± 3% to 27% ± 7% of body mass over winter. Animals with small fat stores might be more reliant on food intake during winter, because proportional fat loss was correlated positively with total fat mass at the start of winter. Fat losses were minimized by lowering rates of energy expenditure. Field metabolic rate was 440 ± 18 kJ kg−0.77 day−1. Water turnovers were slow at 26.62 ml kg−0.75 day−1 in wild porcupines. Body temperatures were not reduced to save energy; core temperatures...