Water drinking induces thermogenesis through osmosensitive mechanisms

Hepatic interoception in health and disease

The liver is a large organ with crucial functions in metabolism and immune defense, as well as blood homeostasis and detoxification, and it is clearly in bidirectional communication with the brain and rest of the body via both neural and humoral pathways. A host of neural sensory mechanisms have been proposed, but in contrast to the gut-brain axis, details for both the exact site and molecular signaling steps of their peripheral transduction mechanisms are generally lacking. Similarly, knowledge about function-specific sensory and motor components of both vagal and spinal access pathways to the hepatic parenchyma is missing. Lack of progress largely owes to controversies regarding selectivity of vagal access pathways and extent of hepatocyte innervation. In contrast, there is considerable evidence for glucose sensors in the wall of the hepatic portal vein and their importance for glucose handling by the liver and the brain and the systemic response to hypoglycemia. As liver diseases are on the rise globally, and there are intriguing associations between liver diseases and mental illnesses, it will be important to further dissect and identify both neural and humoral pathways that mediate hepatocyte-specific signals to relevant brain areas. The question of whether and how sensations from the liver contribute to interoceptive self-awareness has not yet been explored.

Water and beverage consumption habits of adults in Turkey by gender and BMI: a cross-sectional survey

The study aims to determine water and beverage consumption status and related factors in daily nutrition of adults living in Turkey. This study was conducted with 6332 adults aged 18-65 years across Turkey. Demographics and anthropometric data of subjects, their daily water and beverage consumption habits were explored using the retrospective 24-hour recall method. Water and black tea were the most consumed beverages (1801.38 ± 11.06 mL/day, 455 ± 6.10 mL/day, respectively). Increased BMI was associated with a significantly decreased rate of insufficient fluid intake among the participants. Underweight individuals were found to be consuming less (by 0.558 times) fluid compared to those with normal BMI, while obese individuals appeared to have greater energy intake from daily fluid consumption (by 1.111 times). This study showed a relationship between water and beverage intake and anthropometric measurements, suggesting that further research on personalized water intake strategies is beneficial in weight management.

A Study of Fluid Intake, Hydration Status, and Body Composition of Pregnant Women in Their Third Trimester, and Relationships with Their Infant's Birth Weight in China: A Prospective Cohort Study

BACKGROUND

Water intake and hydration status may potentially influence maternal and child health. However, there is little research regarding this topic.

OBJECTIVES

This study aimed to investigate pregnant women's total fluid intake (TFI) levels, hydration status, and body composition and further explore their relationship with infant birth weight.

METHODS

A 7-day, 24 h fluid intake recorded was applied to determine participants' TFI levels. Morning urine samples were collected and tested to evaluate their hydration status. Maternal body compositions in their third trimester and infant birth weights were measured.

RESULTS

A total of 380 participants completed the study. The TFI was insufficient for pregnant women during their third trimester (median = 1574 mL), with only 12.1% of participants meeting the recommended adequate fluid intake level for pregnant women living in China (1.7 L per day). With the increasing TFI values, the urine osmolality decreased, which showed statistical significance among the four groups (χ2 = 22.637, p < 0.05). The participants displayed a poor hydration status. Meanwhile, the percentage of participants who were in dehydrated status decreased (χ2 = 67.618, p < 0.05), while body water content and basal metabolic rate increased with the increase in TFI levels (χ2 = 20.784, p < 0.05; χ2 = 14.026, p < 0.05). There were positive linear relationships between plain water intake, the basal metabolic rate of pregnant women and their infant birth weight (SE = 0.153, p < 0.05; SE = 0.076, p < 0.05).

CONCLUSIONS

Water intake was insufficient, and poor hydration status was common among pregnant women in China. There may be potential relationships between plain water intake, basal metabolic rate, and infant birth weight.

Effect of heat stress on the hypothalamic expression profile of water homeostasis-associated genes in low- and high-water efficient chicken lines

With climate change, selection for water efficiency and heat resilience are vitally important. We undertook this study to determine the effect of chronic cyclic heat stress (HS) on the hypothalamic expression profile of water homeostasis-associated markers in high (HWE)- and low (LWE)-water efficient chicken lines. HS significantly elevated core body temperatures of both lines. However, the amplitude was higher by 0.5-1°C in HWE compared to their LWE counterparts. HWE line drank significantly less water than LWE during both thermoneutral (TN) and HS conditions, and HS increased water intake in both lines with pronounced magnitude in LWE birds. HWE had better feed conversion ratio (FCR), water conversion ratio (WCR), and water to feed intake ratio. At the molecular level, the overall hypothalamic expression of aquaporins (AQP8 and AQP12), arginine vasopressin (AVP) and its related receptor AVP2R, angiotensinogen (AGT), angiotensin II receptor type 1 (AT1), and calbindin 2 (CALB2) were significantly lower; however, CALB1 mRNA and AQP2 protein levels were higher in HWE compared to LWE line. Compared to TN conditions, HS exposure significantly increased mRNA abundances of AQPs (8, 12), AVPR1a, natriuretic peptide A (NPPA), angiotensin I-converting enzyme (ACE), CALB1 and 2, and transient receptor potential cation channel subfamily V member 1 and 4 (TRPV1 and TRPV4) as well as the protein levels of AQP2, however it decreased that of AQP4 gene expression. A significant line by environment interaction was observed in several hypothalamic genes. Heat stress significantly upregulated AQP2 and SCT at mRNA levels and AQP1 and AQP3 at both mRNA and protein levels, but it downregulated that of AQP4 protein only in LWE birds. In HWE broilers, however, HS upregulated the hypothalamic expression of renin (REN) and AVPR1b genes and AQP5 proteins, but it downregulated that of AQP3 protein. The hypothalamic expression of AQP (5, 7, 10, and 11) genes was increased by HS in both chicken lines. In summary, this is the first report showing improvement of growth performances in HWE birds. The hypothalamic expression of several genes was affected in a line- and/or environment-dependent manner, revealing potential molecular signatures for water efficiency and/or heat tolerance in chickens.

The Berlin-Buch respiration chamber for energy expenditure measurements

PURPOSE

We present a methodological overview of a respiration chamber at the Experimental and Clinical Research Center in Berlin, Germany. Since 2010, we investigated 750 healthy subjects and patients with various diseases. We routinely measure resting energy expenditure (REE), dietary-induced thermogenesis, and activity energy expenditure.

METHODS

The chamber is a pull calorimeter with a total volume of 11,000 L. The majority of measurements is done with a flow rate of 120 L/min, yielding a favorable time constant of 1.53 h. The gas analysis system consists of two paramagnetic O₂ sensors and two infrared CO₂ sensors, one for incoming and one for outgoing air samples. O₂ and CO₂ sensors are calibrated simultaneously before each measurement with a 6 min calibration routine. To verify the accuracy of the whole the calorimetric system, it is validated every 2 weeks by 2 h acetone burning tests.

RESULTS

Validation factors (calculated/measured) of 20 representative 2 h acetone burning tests were 1.03 ± 0.03 for [Formula: see text], 1.02 ± 0.02 for [Formula: see text], 0.99 ± 0.02 for RER, and 1.03 ± 0.03 for EE. Four repeated 60 min REE measurements of a healthy woman showed variabilities of 231.9 ± 4.8 ml/min for [Formula: see text] (CV 2.1%), 166.0 ± 6.3 ml/min for [Formula: see text] (CV 3.8%), 0.73 ± 0.03 for RER (CV 4.6%), and 4.55 ± 0.07 kJ/min for EE (CV 1.6%).

CONCLUSIONS

The data presented show that our respiration chamber produces precise and valid EE measurements with an exceptionally fast responsiveness.

The Association between Healthy Beverage Index and Healthy and Unhealthy Obesity Phenotypes among Obese Women: A Cross-Sectional Study

BACKGROUND

Metabolic phenotypes are new dimensions of obesity. Two important types of these phenotypes are metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO). Studies showed that the components of the healthy beverage index (HBI) such as sugar-sweetened beverages (SSBs), milk, and fruit juices might have an association with MHO and MUO phenotypes.

METHODS

This cross-sectional study was performed on 210 women with the age range of 18-65 years and a body mass index (BMI) ≥25 kg/m². The age range of the study population was the main inclusion criterion. Dietary intakes were assessed using a 147-item food frequency questionnaire (FFQ), as well as biochemistry and anthropometric parameters, in all participants. Metabolic health phenotypes were considered using the Karelis score, whilst HBI was evaluated based on 8 categories of beverages consumed. Analysis was carried out using binary logistic regression.

RESULT

After controlling for a wide variety of confounding variables such as age, energy intake, BMI, education, physical activity, marriage, economic status, job, and supplementation, we found that the participants in the highest tertile of HBI had a lower risk of abnormal metabolic status than those in the lowest tertile (OR = 0.49; 95% CI: 0.07-3.21; P trend: 0.04), and it was not statistically significant, but we saw a significant trend.

CONCLUSION

In conclusion, it seems that higher adherence to HBI can minimize the risk of metabolic abnormality, based on a significant trend.

Total water intake by kilogram of body weight: Analysis of the Australian 2011 to 2013 National Nutrition and Physical Activity Survey

AIM

Water is critical for human survival, yet water intake equations may not reflect contemporary populations. This research aims to determine the total water intake of a representative Australian population, per kilogram of body weight (mL/kg) and stratified by age and sex.

METHODS

A secondary analysis of the 2011 to 2013 National Nutrition and Physical Activity Survey (n = 10 146) was conducted. Dietary intake from food and beverages was assessed by a 24-hour recall, with respondent's weight objectively measured. Data were descriptively analysed, with multiple linear regressions used to identify the impact of demographic and physiologic factors on total water intake (mL/kg).

RESULTS

The median (interquartile range) daily total water intake per kilogram of body weight for children (2-8 years), adolescents (9-18 years) and adults (19+ years) were 77.1 (57.4-100) mL/kg, 40.4 (29.3-53.4) mL/kg and 35.5 mL/kg (26.1-47.8), respectively. Increasing height and waist circumference were associated with reduced total water intake, with a change of -1.03 mL/kg (-1.43, -0.618) [coefficient (95% confidence interval)] in children for height and -0.448 mL/kg (-0.484, -0.412) in adults for waist circumference. Similarly, seasonality decreased intake, with greatest reductions in winter [adolescents: -4.11 mL/kg (-6.83, -1.40)]. In comparison, being male, living in rural areas and having a physical occupation were associated with greater intake, by 1.73 mL/kg (0.347, 3.10), 4.74 mL/kg (3.47, 6.00) and 2.82 (trade workers: 1.08, 4.59) in adults, respectively.

CONCLUSIONS

Total water intake (mL/kg) decreased with age in both sexes. The results highlight possibilities to incorporate other factors into water intake equations to improve their accuracy.

Sensory Circumventricular Organs, Neuroendocrine Control, and Metabolic Regulation

The central nervous system is critical in metabolic regulation, and accumulating evidence points to a distributed network of brain regions involved in energy homeostasis. This is accomplished, in part, by integrating peripheral and central metabolic information and subsequently modulating neuroendocrine outputs through the paraventricular and supraoptic nucleus of the hypothalamus. However, these hypothalamic nuclei are generally protected by a blood-brain-barrier limiting their ability to directly sense circulating metabolic signals—pointing to possible involvement of upstream brain nuclei. In this regard, sensory circumventricular organs (CVOs), brain sites traditionally recognized in thirst/fluid and cardiovascular regulation, are emerging as potential sites through which circulating metabolic substances influence neuroendocrine control. The sensory CVOs, including the subfornical organ, organum vasculosum of the lamina terminalis, and area postrema, are located outside the blood-brain-barrier, possess cellular machinery to sense the metabolic interior milieu, and establish complex neural networks to hypothalamic neuroendocrine nuclei. Here, evidence for a potential role of sensory CVO-hypothalamic neuroendocrine networks in energy homeostasis is presented.

Baseline drinking water consumption and changes in body weight and waist circumference at 2-years of follow-up in a senior Mediterranean population

BACKGROUND & AIMS

The association between drinking water consumption and adiposity has been poorly explored. Therefore, we aimed to analyse the associations between the frequency of drinking water consumption and body weight and waist circumference changes in an elderly Mediterranean cohort.

METHODS

A total of 1832 elderly participants (aged 55-75 years) with metabolic syndrome from the PREDIMED-Plus study with baseline data on drinking water and other beverages assessed by a validated 32-item Spanish fluid-intake questionnaire and with data on body weight (BW) and waist circumference (WC) at 1-year and 2-year were included in these prospective analyses. Multivariable linear regression models were fitted to assess the β-coefficients and 95% confidence interval (CI) for BW and WC changes in terms of categories of baseline drinking water consumption (tap water and bottled water). The theoretical effect on BW and WC of replacing several beverages with drinking water was assessed using mathematical models.

RESULTS

The baseline frequency of drinking water consumption was inversely associated with 1-year and 2-year changes in BW. β-coefficients (95%CI) across categories of water consumption (<2.5, 2.5 to <5, 5 to < 7.5, ≥7.5 servings/d) expressed in % of weight changes at 2 years of follow-up were 0.0, -0.80 (-1.48, -0.12), -1.36 (-2.18, -0.54), and -1.97 (-3.09, -0.86), respectively. Individuals in the two highest categories of drinking water consumption (5 to < 7, and ≥7.5 servings/d) also showed a higher decrease in WC (expressed as % of change) after 2 years of follow-up: -1.11 (-1.96, -0.25) and -1.45 (-2.66, -0.24) compared to the reference intake (<2.5 servings/day), after adjustment for potential confounding factors. The theoretical replacement of soups, beers, spirits, hot beverages, dairy beverages, and other beverages group with drinking water was associated with greater reductions in BW at one- and two-years of follow-up.

CONCLUSIONS

Drinking water consumption was inversely associated with 2-year adiposity changes in an elderly Mediterranean cohort at high cardiovascular risk. Our results also suggest that the consumption of drinking water instead of energy-containing beverages is associated with lower weight gain.

THE TRIAL REGISTRATION

ISRCTN89898870.

Effect of temperature and/or sweetness of beverages on body composition in rats

Sweetened beverages are mainly consumed cold and various processes are activated in response to external temperature variations. However, the effect of internal temperature variations through the ingestion of cold beverages is far from clear. Two experiments were conducted to investigate the effect of beverage temperature on body composition. Sprague-Dawley rats (5-6-week-old males) had free access to food and beverage for 8 weeks. Energy intake, body weight and body composition were monitored. In Expt 1, two groups of rats (n 9) consumed water at room temperature (NW about 22°C) or cold (CW about 4°C). In Expt 2, rats were offered room-temperature (N) or cold (C) sweetened water (10 % sucrose CSu (n 7) and NSu (n 8); or 0·05 % acesulfame K CAk (n 6) and NAk (n 8)) for 12 h, followed by plain water. Our results show that in Expt 1, CW had higher lean body mass (P < 0·001) and lower body fat gain (P = 0·004) as compared with NW. In Expt 2, body weight (P = 0·013) and fat (P ≤ 0·001) gains were higher in the non-energetic sweetened groups, while lean body mass was not affected by the type of sweeteners or temperature. In conclusion, cold water ingestion improved lean body mass gain and decreased fat gain because of increased energy expenditure, while non-energetic sweetener (acesulfame K) increased body fat gain due to improved energy efficiency. Internal cold exposure failed to increase energy intake in contrast to that of external cold exposure.

Transcription Factor TonEBP Stimulates Hyperosmolality-Dependent Arginine Vasopressin Gene Expression in the Mouse Hypothalamus

The hypothalamic neuroendocrine system is strongly implicated in body energy homeostasis. In particular, the degree of production and release of arginine vasopressin (AVP) in the hypothalamus is affected by plasma osmolality, and that hypothalamic AVP is responsible for thirst and osmolality-dependent water and metabolic balance. However, the osmolality-responsive intracellular mechanism within AVP cells that regulates AVP synthesis is not clearly understood. Here, we report a role for tonicity-responsive enhancer binding protein (TonEBP), a transcription factor sensitive to cellular tonicity, in regulating osmosensitive hypothalamic AVP gene transcription. Our immunohistochemical work shows that hypothalamic AVP cellular activity, as recognized by c-fos, was enhanced in parallel with an elevation in TonEBP expression within AVP cells following water deprivation. Interestingly, our in vitro investigations found a synchronized pattern of TonEBP and AVP gene expression in response to osmotic stress. Those results indicate a positive correlation between hypothalamic TonEBP and AVP production during dehydration. Promoter and chromatin immunoprecipitation assays confirmed that TonEBP can bind directly to conserved binding motifs in the 5'-flanking promoter regions of the AVP gene. Furthermore, dehydration- and TonEBP-mediated hypothalamic AVP gene activation was reduced in TonEBP haploinsufficiency mice, compared with wild TonEBP homozygote animals. Therefore, our result support the idea that TonEBP is directly necessary, at least in part, for the elevation of AVP transcription in dehydration conditions. Additionally, dehydration-induced reductions in body weight were rescued in TonEBP haploinsufficiency mice. Altogether, our results demonstrate an intracellular machinery within hypothalamic AVP cells that is responsible for dehydration-induced AVP synthesis.

Lowered blood pressure targets identify new, uncontrolled hypertensive cases: patient characteristics and implications for services in Thailand

BACKGROUND

According to the new hypertension treatment guidelines blood pressure (BP) readings need to be kept below or equal to 130/80 mmHg in patients aged less than 65 years old. This study shows the change in proportion of identified cases of uncontrolled blood pressure in light of these changes.

METHODS

The data was collected from 248 hypertensive patients who had visited an outpatient clinic at the Department of Family Medicine, Faculty of Medicine, Chiang Mai University, Thailand. Patients were classified into three groups: The 3 groups were: 1) controlled BP group (BP is 130/80 mmHg or lower); 2) newly identified uncontrolled group (BP between 130/80 mmHg and 140/90 mmHg) and 3) existing uncontrolled group (BP higher than 140/90 mmHg). Health behaviors, past history related to hypertensive disease and current pharmacological treatments were compared.

RESULTS

Of the total 248 patients, 56% were female and the mean age was 58.8 (sd 5.99) years old. Following application of the new guidelines, the group designated as uncontrolled increased from 21.7 to 74.2%, an additional 52.4% due to new BP targets. Higher BMI was associated with uncontrolled HT (p = 0.043). While the average number of medication taken was similar across the three groups, it was poor medication adherence (p < 0.013) which was associated with the uncontrolled disease.

CONCLUSIONS

Lower BP targets will increase the number of identified hypertensive patients. While intensifying pharmacological treatment may be considered, our study suggests that two behavioral factors should not be overlooked. Weight reduction and enhancement of medication adherence remains an important mainstream treatment strategy.

Portal vein innervation underlying the pressor effect of water ingestion with and without cold stress

Water-induced pressor response appears mediated through the activation of transient receptor potential channel TRPV4 on hepatic portal circulation in animals. We sought to elucidate the mechanism of portal vein signaling in this response. Forty-five rats were divided into four groups: control rats without water ingestion (WI), control rats with WI, portal vein denervation rats with WI (PVDWI), and TRPV4 antagonist-treated rats with WI (anti-TRPV4WI). Cardiovascular responses were monitored throughout the experiments. Data analysis was performed using descriptive methods and spectral and cross-spectral analysis of blood pressure variability (BPV) and heart rate variability (HRV). Key results showed that at baseline (PreCS) before cold stress trial (CS), WI elicited robust pressor and tachycardia responses accompanied by spectral power changes, in particular, increases of low-frequency BPV (LFBPV) and very-LFBPV (VLFBPV), but decrease of very-low-frequency HRV. PVDWI, likewise, elicited pressor and tachycardia responses accompanied by increases of high-frequency BPV, high-frequency HRV, LFBPV, low-frequency HRV, and VLFBPV. When compared with WI at PreCS, WI at CS elicited pressor and tachycardia responses accompanied by increases of high-frequency BPV, LFBPV, and VLFBPV, whereas in WI, the CS-evoked pressor response and the accompanied LFBPV and VLFBPV increases were all tended augmented by PVDWI. When compared with WI and PVDWI at both PreCS and CS, however, anti-TRPV4WI attenuated their pressor responses and attenuated their increased LFBPV, VLFBPV, and very-low-frequency HRV. The results indicate that the portal vein innervation is critical for a buffering mechanism in splanchnic sympathetic activation and water-induced pressor response.

Dose-dependent heart rate responses to drinking water: a randomized crossover study in young, non-obese males

PURPOSE

The aim of the study was to explore a potential dose effect of water on heart rate responses and markers of vagal tone modulation.

METHODS

This was a randomized crossover study involving eight men whose heart rate and heart rate variability parameters were continuously measured following ingestion of different volumes of still mineral water (200, 400, 600, and 800 mL).

RESULTS

A significant volume by time effect for heart rate (p < 0.005) was observed. Ingestion of all volumes of drink water of more 200 mL significantly decreased the heart rate. Significant time effects for heart rate variability parameters were observed.

CONCLUSION

Ingestion of a mineral water drink affected the heart rate in men in a time-dependent manner, possibly by changes in cardiac vagal modulation.

Hyperthermia induced by transient receptor potential vanilloid-1 (TRPV1) antagonists in human clinical trials: Insights from mathematical modeling and meta-analysis

Antagonists of the transient receptor potential vanilloid-1 (TRPV1) channel alter body temperature (T_b) in laboratory animals and humans: most cause hyperthermia; some produce hypothermia; and yet others have no effect. TRPV1 can be activated by capsaicin (CAP), protons (low pH), and heat. First-generation (polymodal) TRPV1 antagonists potently block all three TRPV1 activation modes. Second-generation (mode-selective) TRPV1 antagonists potently block channel activation by CAP, but exert different effects (e.g., potentiation, no effect, or low-potency inhibition) in the proton mode, heat mode, or both. Based on our earlier studies in rats, only one mode of TRPV1 activation - by protons - is involved in thermoregulatory responses to TRPV1 antagonists. In rats, compounds that potently block, potentiate, or have no effect on proton activation cause hyperthermia, hypothermia, or no effect on T_b, respectively. A T_b response occurs when a TRPV1 antagonist blocks (in case of hyperthermia) or potentiates (hypothermia) the tonic TRPV1 activation by protons somewhere in the trunk, perhaps in muscles, and - via the acido-antithermogenic and acido-antivasoconstrictor reflexes - modulates thermogenesis and skin vasoconstriction. In this work, we used a mathematical model to analyze T_b data from human clinical trials of TRPV1 antagonists. The analysis suggests that, in humans, the hyperthermic effect depends on the antagonist's potency to block TRPV1 activation not only by protons, but also by heat, while the CAP activation mode is uninvolved. Whereas in rats TRPV1 drives thermoeffectors by mediating pH signals from the trunk, but not T_b signals, our analysis suggests that TRPV1 mediates both pH and thermal signals driving thermoregulation in humans. Hence, in humans (but not in rats), TRPV1 is likely to serve as a thermosensor of the thermoregulation system. We also conducted a meta-analysis of T_b data from human trials and found that polymodal TRPV1 antagonists (ABT-102, AZD1386, and V116517) increase T_b, whereas the mode-selective blocker NEO6860 does not. Several strategies of harnessing the thermoregulatory effects of TRPV1 antagonists in humans are discussed.

Association between Hydration Status and Body Composition in Healthy Adolescents from Spain

At present, obesity and overweight are major public health concerns. Their classical determinants do not sufficiently explain the current situation and it is urgent to investigate other possible causes. In recent years, it has been suggested that water intake could have important implications for weight management. Thus, the aim of this study was to examine the effect of hydration status on body weight and composition in healthy adolescents from Spain. The study involved 372 subjects, aged 12-18 years. Water intake was assessed through the validated "hydration status questionnaire adolescent young". Anthropometric measurements were performed according to the recommendations of the International Standards for Anthropometric Assessment (ISAK) and body composition was estimated by bioelectrical impedance analysis. Water intake normalized by body weight was positively correlated with body water content (boys (B): r = 0.316, p = 0.000; girls (G): r = 0.245, p = 0.000) and inversely with body mass index (BMI) (B: r = -0.515, p = 0.000; G: r = -0.385, p =0.000) and fat body mass (B: r = -0.306, p = 0.000; G: r = -0.250, p = 0.001). Moreover, according to BMI, overweight/obese individuals consumed less water than normal weight ones. In conclusion, higher water balance and intake seems to be related with a healthier body composition. In conclusion, higher water balance and intake is associated with a healthier body composition.

Influence of Water Intake and Balance on Body Composition in Healthy Young Adults from Spain

The increasing prevalence of overweight and obesity has become an epidemic public health problem worldwide. In the last years, several investigations have suggested that water intake and retention could have important implications for both weight management and body composition. However, there is a lack of information about this issue globally, and mainly specifically in Spain. Thus, the aim of this study was to analyze the association between hydration status and body composition in a sample of healthy Spanish adults. The study involved 358 subjects, aged 18-39 years. The recently validated "hydration status questionnaire" was used to assess their water intake, elimination, and balance. Anthropometric measurements were performed according to the recommendations of the International Standards for Anthropometric Assessment (ISAK). Body composition variables were acquired by bioelectrical impedance analysis. Differences in anthropometric and body composition variables were assessed through the ANOVA test and considered significant at p < 0.05. Fluid intake was correlated with body water content. Inverse associations between water consumption, normalized by weight, with body weight, body fat mass, and waist circumference were found. Moreover, according to water balance, significant differences in body water content in females were observed. In conclusion, higher fluid intake seems to be related with a healthier body composition. Therefore, the improvement of water intake and water balance could be useful for overweight and obesity prevention, although further studies are needed to confirm the present findings.

Hydration biomarkers and copeptin: relationship with ad libitum energy intake, energy expenditure, and metabolic fuel selection

Background/Objective

Evidence from non-human species indicate that hydration and arginine vasopressin (AVP) influence fuel selection, energy expenditure (EE), and food intake, but these relationships are unclear in humans. We sought to assess whether hydration biomarkers [24-h urine volume (UVol) and urine urea nitrogen concentration (UUN)] and copeptin (a surrogate for AVP) are associated with 24-h EE, respiratory quotient (RQ), and daily energy intake (DEI).

Subjects/Methods

In a secondary analysis of collected data, we selected healthy adults (Group 1, n = 177) who had 24-h whole-room indirect calorimetry measurements in energy balance with 24-h urine collection and fasting copeptin measurements (n=117), followed by 3 days ad libitum food intake. A separate group (Group 2, n=284) with hydration markers and calorimetry measurements was also studied. The main outcome measures were 24-h RQ, 24-h EE, DEI, substrate oxidation.

Results

In Group 1, lower 24-h UVol and higher 24-h UUN, indicating lower hydration, were correlated with lower 24-h RQ (r = 0.35, p <0.0001, and r = −0.29, p = 0.0001, respectively; results similar in Group 2) and predicted subsequent reduced DEI (r = 0.20, p = 0.01, and r = −0.27, p = 0.0003, respectively), adjusted for confounders. Copeptin was independently associated with 24-h lipid oxidation (r = −0.23, p = 0.01). In Group 2, lower hydration was associated with reduced 24-h EE (24-h UVol: r = 0.29, p <0.0001; 24-h UUN: r = −0.25, p <0.0001).

Conclusions

Hydration biomarkers were associated with metabolic differences characterized by altered food intake, fuel selection, and possibly EE. Independently, copeptin was associated with higher lipid oxidation.

Analysis of 2009⁻2012 Nutrition Health and Examination Survey (NHANES) Data to Estimate the Median Water Intake Associated with Meeting Hydration Criteria for Individuals Aged 12⁻80 in the US Population

In 2005, US water intake recommendations were based on analyses of Nutrition Health and Examination Surveys (NHANES) III data that examined if hydration classification varied by water intake and estimated the median water intake associated with hydration in persons aged 19–30. Given the upcoming 2020–2025 Dietary Guidelines review, this analysis addressed the same two aims with 2009–2012 NHANES data. Methods were updated by defining hydration criteria in terms of multiple measures (serum sodium 135–144 mmol/L and urine osmolality < 500 mmol/kg), expressing water intake as ml/kg, distinguishing plain water intake (PWI) from total water intake (TWI), using weighted age- and sex-specific multivariable models to control for determinants of water intake requirements, and selecting two study samples (the non-acutely ill US population and a sub-group without selected chronic disease risk factors). In the US population and sub-group, the relative risk (RR) of meeting the hydration criteria was significantly greater for individuals with TWI ≥ 45 mL/kg or PWI ≥ 20 mL/kg (for the US population 19–50 years of age: adjusted RR = 1.36, 95% CI: 1.10–1.68 for males; adjusted RR = 1.70, 95% CI: 1.49–1.95 for females. For the sub-group 51–70 years of age: adjusted RR = 2.20, 95% CI: 1.15–4.18 for males; adjusted RR = 2.00, 95% CI: 1.18–3.40 for females). The median (SE) TWI and PWI associated with meeting the hydration criteria for males and females 19–50 years of age were 42 (2) mL/kg and 14 (1) mL/kg and 43 (2) mL/kg and 16 (1) mL/kg, respectively. The significant association between water intake and hydration classification differs from the null association underlying the 2005 water intake recommendations and may lead to different reasoning and inferences for the 2020–2025 Dietary Guidelines.

Inter-correlations Among Clinical, Metabolic, and Biochemical Parameters and Their Predictive Value in Healthy and Overtrained Male Athletes: The EROS-CORRELATIONS Study

Objectives: The Endocrine and Metabolic Responses on Overtraining Syndrome (EROS) study identified multiple hormonal and metabolic conditioning processes in athletes, and underlying mechanisms and biomarkers of overtraining syndrome (OTS). The present study's objective was to reveal independent predictors and linear correlations among the parameters evaluated in the EROS study to predict clinical, metabolic, and biochemical behaviors in healthy and OTS-affected male athletes. Methods: We used multivariate linear regression and linear correlation to analyze possible combinations of the 38 parameters evaluated in the EROS study that revealed significant differences between healthy and OTS-affected athletes. Results: The testosterone-to-estradiol (T:E) ratio predicted the measured-to-predicted basal metabolic rate (BMR) ratio; the T:E ratio and total testosterone level were inversely predicted by fat mass and estradiol was not predicted by any of the non-modifiable parameters. Early and late growth hormone, cortisol, and prolactin responses to an insulin tolerance test (ITT) were strongly correlated. Hormonal responses to the ITT were positively correlated with fat oxidation, predicted-to-measured BMR ratio, muscle mass, and vigor, and inversely correlated with fat mass and fatigue. Salivary cortisol 30 min after awakening and the T:E ratio were inversely correlated with fatigue. Tension was inversely correlated with libido and directly correlated with body fat. The predicted-to-measured BMR ratio was correlated with muscle mass and body water, while fat oxidation was directly correlated with muscle mass and inversely correlated with fat mass. Muscle mass was directly correlated with body water, and extracellular water was directly correlated with body fat and inversely correlated with body water and muscle mass. Conclusions: Hypothalamic-pituitary responses to stimulation were diffuse and indistinguishable between the different axes. A late hormonal response to stimulation, increased cortisol after awakening, and the T:E ratio were correlated with vigor and fatigue. The T:E ratio was also correlated with body metabolism and composition, testosterone was predicted by fat mass, and estradiol predicted anger. Hydration status was inversely correlated with edema, and inter-correlations were found among fat oxidation, hydration, and body fat.

Complementary and compensatory dietary changes associated with consumption or omission of plain water by US adults

We examined within-person and between-person differences in self-selected diets of free-living individuals when they choose to consume or not to consume plain water. We used 2-days of dietary data from the NHANES 2005-2012 for this study. For within-person analyses, we compared recalls of respondents who reported water in one of the two available recalls (n = 1875 men and 1479 women). For between-person analysis, we compared dietary recalls of respondents who reported water in two, one of two, or zero of two recalls (n = 8632 men and 8907 women). The outcomes examined included reported intakes of 24-h energy from foods, beverages, and dietary and eating pattern attributes. We used covariate-adjusted regression methods for both types of analyses. For within-person analyses, the regression models included separate person-level fixed effects. Relative to the water day, on the no-water day, amount of beverages and energy contribution of beverages were significantly higher in both men (106 kcal) and women (43 kcal) (P ≤ 0.002). However, the water and the no-water days did not differ in 24-h energy intake, or the amount and energy from reported foods (P > 0.05). Energy density of foods, servings of fruits or vegetables and eating patterns did not differ between the water and the no-water day in both men and women (P > 0.05). For between-person analysis, however, intakes of energy and energy density of foods were higher, but density of sodium, potassium, and magnesium were lower among those who reported no water in both recalls. Overall, beverages partially substituted for plain water on the no-water day but qualitative dietary characteristics and eating patterns, which may relate to habitual food intake and personal preferences, were not appreciably different within individuals.

The Hormone FGF21 Stimulates Water Drinking in Response to Ketogenic Diet and Alcohol

Alcohol and ketogenic diets increase water consumption. Here, we show that the hormone FGF21 is required for this drinking response in mice. Circulating levels of FGF21 are increased by alcohol consumption in humans and by both alcohol and ketogenic diets in mice. Pharmacologic administration of FGF21 stimulates water drinking behavior in mice within 2 hr. Concordantly, mice lacking FGF21 fail to increase water intake in response to either alcohol or a ketogenic diet. The effect of FGF21 on drinking is mediated in part by SIM1-positive neurons of the hypothalamus and is inhibited by β-adrenergic receptor antagonists. Given that FGF21 also is known to suppress alcohol intake in favor of pure water, this work identifies FGF21 as a fundamental neurotropic hormone that governs water balance in response to specific nutrient stresses that can cause dehydration.

Cross-sectional association of dietary water intakes and sources, and adiposity: National Adult Nutrition Survey, the Republic of Ireland

Purpose

Drinking (plain) water intake has been associated with weight loss and reducing energy intake in intervention trials. In free-living populations, replacing other beverages with drinking water is associated with reduced obesity risk. However, the association of total water intake and its sources, and body fat distribution remain unevaluated. Thus, the aim of this study was to investigate total water intake and its sources and the association with anthropometric measures.

Methods

Cross-sectional study of 1500 adults aged 18–90 years (Irish National Adult Nutrition Survey, 2008–2010). Total water intake and its sources were estimated using food records. Associations of total water, drinking water, beverage moisture and food moisture intakes split by tertile, and BMI (kg/m²), waist circumference (cm), and bio-impedance derived body fat (%) were evaluated using covariate-adjusted linear regression analyses including adjustment for energy intake and energy expenditure.

Results

Higher consumption of total water was associated with lower waist circumference [β-coefficient (95% CI), p trend, tertile 3 versus tertile 1: − 2.19 (− 4.06, − 0.32), 0.036], but not BMI [− 0.44 (− 1.16, 0.28), 0.336] or body fat [− 0.87 (− 1.91, 0.17), 0.146]. Higher consumption of drinking water and food moisture were associated with lower BMI [− 0.65 (− 1.30, − 0.01), 0.027; − 0.64 (− 1.41, − 0.13), 0.014, respectively], body fat [− 1.51 (− 2.43, − 0.59), 0.001; − 1.00 (− 2.12, − 0.12), 0.001], and waist circumference [− 2.83 (− 4.51, − 1.16), < 0.001; − 1.84 (− 3.86, − 0.19), 0.082]. Beverage moisture was not associated with any of the anthropometric measurements.

Conclusions

Consumption of drinking water and food moisture and not total water or beverage moisture were inversely associated with adiposity, independent of energy intake and expenditure. Advice encouraging drinking water and food moisture intake may be beneficial in addition to energy balance advice, in combating obesity.

Electronic supplementary material

The online version of this article (10.1007/s00394-018-1635-z) contains supplementary material, which is available to authorized users.

Hydration and obesity among outpatient-based population: H2Ob study

Recent evidence suggests that obese people are hypohydrated and that water consumption may be a useful indicator for the prevention and treatment of obesity. Nevertheless, there is no agreement regarding the best hydration status indicators and there are few data about the relationship between hydration and body weight. In the present study, we aim to analyze the correlation among hydration status with obesity measured by three different methods (plasma osmolarity, urinary specific gravity (USG) and urinary osmolarity) in a hospital-based outpatient population. We have carried out a cross-sectional study to evaluate the association between obesity and hydration status in 260 patients, average 56.5±15.7 years. Hydration status was estimated by means of plasma osmolarity, urine osmolarity and USG. We did show significant trend of higher urine osmolarity (P=0.03), USG (P=0.000) and plasma osmolarity (P=0.000) with an increase of weight status categories, more accurate in the case of plasma osmolarity. In a multivariate analysis, after controlled by confounders, we found that obesity was associated with plasma osmolarity (OR 1.09; 95% CI 1.02 to 1.17, P=0.009), urine osmolarity (OR 1.00; 95% CI 1.00 to 1.01, P=0.05) and USG (OR 1.02; 95% CI 1.00 to 1.04, P=0.05). Our results have shown a more accurate relationship between plasma osmolarity with all body mass index categories. This finding may have clinical implications that must be confirmed in further studies.

Effects of Advice to Drink 8 Cups of Water per Day in Adolescents With Overweight or Obesity: A Randomized Clinical Trial

IMPORTANCE

Health care professionals commonly recommend increased water consumption, typically to 8 cups per day, as part of a weight-reducing diet. However, this recommendation is based on limited evidence and virtually no experimental data from the pediatric population.

OBJECTIVE

To compare 2 standardized weight-loss diets among adolescents with overweight or obesity, either with or without additional advice and behavioral support to increase habitual water intake to 8 cups per day.

DESIGN, SETTING, AND PARTICIPANTS

A randomized clinical, parallel-group trial was conducted between February 2, 2011, and June 26, 2014, at Boston Children's Hospital, Boston, Massachusetts, among 38 adolescents with overweight or obesity who reported drinking 4 cups or less of water per day.

INTERVENTIONS

All participants in both groups received similar weight-reducing interventions, differentiated by advice about water intake (the water group received advice to increase water intake to 8 cups per day; the control group did not receive such advice) but controlled for other dietary recommendations and treatment intensity. The interventions included dietary counseling, daily text messages, and a cookbook with health guides. To support adherence to 8 cups of water per day, the water group received well-defined messages about water through counseling and daily text messages, a water bottle, and a water pitcher with filters.

MAIN OUTCOMES AND MEASURES

The primary outcome was 6-month change in body mass index z score. Data analyses followed the intention-to-treat principle.

RESULTS

All 38 participants (27 girls and 11 boys; mean [SD] age, 14.9 [1.7] years) completed the study. Both groups reported drinking approximately 2 cups of water per day at baseline. Self-reported change in water intake at 6 months was greater in the water group (difference from baseline, 2.8 cups per day [95% CI, 1.8 to 3.8]; P < .001) compared with that in the control group (difference from baseline, 1.2 cups per day [95% CI, 0.2 to 2.2]; P = .02) (difference between groups, 1.6 cups per day [95% CI, 0.2 to 3.0 cups per day]; P = .03). The 6-month change in body mass index z score did not differ between the water group (difference from baseline, -0.1 [95% CI, -0.2 to -0.0]; P = .005) and the control group (difference from baseline, -0.1 [95% CI, -0.2 to -0.0]; P = .008) (difference between groups, -0.0 [95% CI, -0.1 to 0.1]; P = .88).

CONCLUSIONS AND RELEVANCE

Advice and behavioral supports to consume 8 cups of water per day in the context of a weight-reducing diet did not affect body weight among adolescents with overweight or obesity. Despite intensive behavior supports, few adolescents achieved the target of 8 cups of water per day. Environmental interventions to reduce barriers to water consumption at school may be necessary in future research of the feasibility and effectiveness to achieve the target of an intake of 8 cups of water per day in adolescents.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01044134.

Tea catechin and caffeine activate brown adipose tissue and increase cold-induced thermogenic capacity in humans

Background: The thermogenic effects of green tea catechin have been repeatedly reported, but their mechanisms are poorly understood.Objective: The aim of this study was to investigate the acute and chronic effects of catechin on brown adipose tissue (BAT), a site specialized for nonshivering thermogenesis, in humans.Design: Fifteen healthy male volunteers underwent fluorodeoxyglucose-positron emission tomography to assess BAT activity. To examine the acute catechin effect, whole-body energy expenditure (EE) after a single oral ingestion of a beverage containing 615 mg catechin and 77 mg caffeine (catechin beverage) was measured. Next, to investigate the chronic catechin effects, 10 men with low BAT activity were enrolled. Before and after ingestion of the catechin beverage 2 times/d for 5 wk, cold-induced thermogenesis (CIT) after 2 h of cold exposure at 19°C, which is proportional to BAT activity, was examined. Both the acute and chronic trials were single-blinded, randomized, placebo-controlled, season-matched crossover studies.Results: A single ingestion of the catechin beverage increased EE in 9 subjects who had metabolically active BAT (mean ± SEM: +15.24 ± 1.48 kcal, P < 0.01) but not in 6 subjects who had negligible activities (mean ± SEM: +3.42 ± 2.68 kcal). The ingestion of a placebo beverage containing 82 mg caffeine produced a smaller and comparative EE response in the 2 subject groups. Multivariate regression analysis revealed a significant interaction between BAT and catechin on EE (β = 0.496, P = 0.003). Daily ingestion of the catechin beverage elevated mean ± SEM CIT (from 92.0 ± 26.5 to 197.9 ± 27.7 kcal/d; P = 0.009), whereas the placebo beverage did not change it.Conclusion: Orally ingested tea catechin with caffeine acutely increases EE associated with increased BAT activity and chronically elevates nonshivering CIT, probably because of the recruitment of BAT, in humans. These trials were registered at www.umin.ac.jp/ctr/ as UMIN000016361.

Antiobesity Effects of Hydroethanolic Extract of Jacaranda decurrens Leaves

Obesity is a worldwide epidemic that reduces life expectancy; therefore, the search for new alternative and effective treatments is ongoing. The aim of the present investigation was to identify the chemical compounds in the hydroethanolic extract of leaves of Jacaranda decurrens subsp. symmetrifoliolata and to evaluate their toxicity and antiobesity effects. High-performance liquid chromatography was used to identify the chemical constituents, and acute toxicity was evaluated in rats treated with doses of 2 and 5 g·kg-1 body mass. The antiobesity effect was determined in rats with hypercaloric diet-induced obesity. Our results revealed the presence of compounds, such as jacaric, ursolic, and oleic acids, as well as luteolin, quercetin, and kaempferol, in the extract. The acute toxicity tests revealed that rats treated with elevated doses of the extract showed no signs of toxicity. The extract induced reduction in total body mass and the white adipose tissue depots. The obese rats treated with the extract showed an increased fluid intake and feces excretion while their serum total cholesterol and triglyceride levels decreased compared to those in the controls, without any hematological changes. Taken together, the results showed that the constituents of J. decurrens extracts included phenolic compounds and exhibited antiobesity effects with no toxicity.

Substitution Models of Water for Other Beverages, and the Incidence of Obesity and Weight Gain in the SUN Cohort

Obesity is a major epidemic for developed countries in the 21st century. The main cause of obesity is energy imbalance, of which contributing factors include a sedentary lifestyle, epigenetic factors and excessive caloric intake through food and beverages. A high consumption of caloric beverages, such as alcoholic or sweetened drinks, may particularly contribute to weight gain, and lower satiety has been associated with the intake of liquid instead of solid calories. Our objective was to evaluate the association between the substitution of a serving per day of water for another beverage (or group of them) and the incidence of obesity and weight change in a Mediterranean cohort, using mathematical models. We followed 15,765 adults without obesity at baseline. The intake of 17 beverage items was assessed at baseline through a validated food-frequency questionnaire. The outcomes were average change in body weight in a four-year period and new-onset obesity and their association with the substitution of one serving per day of water for one of the other beverages. During the follow-up, 873 incident cases of obesity were identified. In substitution models, the consumption of water instead of beer or sugar-sweetened soda beverages was associated with a lower obesity incidence (the Odds Ratio (OR) 0.80 (95% confidence interval (CI) 0.68 to 0.94) and OR 0.85 (95% CI 0.75 to 0.97); respectively) and, in the case of beer, it was also associated with a higher average weight loss (weight change difference = −328 g; (95% CI −566 to −89)). Thus, this study found that replacing one sugar-sweetened soda beverage or beer with one serving of water per day at baseline was related to a lower incidence of obesity and to a higher weight loss over a four-year period time in the case of beer, based on mathematical models.

Increased Hydration Can Be Associated with Weight Loss

This mini-review develops the hypothesis that increased hydration leads to body weight loss, mainly through a decrease in feeding, and a loss of fat, through increased lipolysis. The publications cited come from animal, mainly rodent, studies where manipulations of the central and/or the peripheral renin–angiotensin system lead to an increased drinking response and a decrease in body weight. This hypothesis derives from a broader association between chronic hypohydration (extracellular dehydration) and raised levels of the hormone angiotensin II (AngII) associated with many chronic diseases, such as obesity, diabetes, cancer, and cardiovascular disease. Proposed mechanisms to explain these effects involve an increase in metabolism due to hydration expanding cell volume. The results of these animal studies often can be applied to the humans. Human studies are consistent with this hypothesis for weight loss and for reducing the risk factors in the development of obesity and type 2 diabetes.

INGESTÃO DE ÁGUA NO SISTEMA NERVOSO AUTÔNOMO: UMA REVISÃO SISTEMÁTICA E META-ANÁLISE

RESUMO Verificar, por meio de uma revisão sistemática, o efeito da ingestão de água (IA) no sistema nervoso autônomo (SNA) e variáveis hemodinâmicas em indivíduos adultos. Foram analisados estudos publicados entre 2000 e 2015, tendo como referência a base de dados Medline via Pubmed, sendo utilizado na construção da frase de pesquisa o MeSH. Foram estabelecidos os seguintes critérios de inclusão: ensaios clínicos controlados e randomizados (ECCR) realizados em humanos, na língua inglesa. Como critério de exclusão: intervenções pouco claras, mal descritas ou inadequadas e na forma de resumos. Utilizou-se as seguintes variáveis para a seleção dos estudos: frequência cardíaca (FC), pressão arterial (PA), componente de alta frequência (AF) e resistência vascular periférica (RVP). Foi usada a sistematização PRISMA para a elaboração desta revisão e a realização de uma meta-análise com o objetivo de evidenciar matematicamente os resultados da frequência cardíaca após a ingestão de água em sete estudos que avaliaram esta variável. Fizeram parte desta revisão 10 ECCR envolvendo 246 indivíduos com idade entre 19 a 64 anos, sendo que 34,55% do sexo masculino. A maioria dos ECCR analisados apresentou alterações após a IA. As alterações comumente observadas foram: diminuição da FC (estatisticamente significativa p < 0,001), aumento da AF e RVP. Contudo, em relação à PA, os resultados demonstraram-se conflitantes, com estudos que evidenciaram aumento e outros que não observaram diferença significativa. Esta revisão evidencia os efeitos da IA no SNA, em especial na FC, AF e RVP, não obstante em relação às alterações hemodinâmicas expressas pela PA permanece ainda um óbice em relação à comunidade científica.

Negative, Null and Beneficial Effects of Drinking Water on Energy Intake, Energy Expenditure, Fat Oxidation and Weight Change in Randomized Trials: A Qualitative Review

Drinking water has heterogeneous effects on energy intake (EI), energy expenditure (EE), fat oxidation (FO) and weight change in randomized controlled trials (RCTs) involving adults and/or children. The aim of this qualitative review of RCTs was to identify conditions associated with negative, null and beneficial effects of drinking water on EI, EE, FO and weight, to generate hypotheses about ways to optimize drinking water interventions for weight management. RCT conditions that are associated with negative or null effects of drinking water on EI, EE and/or FO in the short term are associated with negative or null effects on weight over the longer term. RCT conditions that are associated with lower EI, increased EE and/or increased FO in the short term are associated with less weight gain or greater weight loss over time. Drinking water instead of caloric beverages decreases EI when food intake is ad libitum. Drinking water increases EE in metabolically-inflexible, obese individuals. Drinking water increases FO when blood carbohydrate and/or insulin concentrations are not elevated and when it is consumed instead of caloric beverages or in volumes that alter hydration status. Further research is needed to confirm the observed associations and to determine if/what specific conditions optimize drinking water interventions for weight management.

Water-induced thermogenesis and fat oxidation: a reassessment

Background/Objectives:

Drinking large amounts of water is often recommended for weight control. Whether water intake stimulates energy and fat metabolism is, however, controversial with some studies reporting that drinking half a litre or more of water increases resting energy expenditure (REE) by 10–30% and decreases respiratory quotient (RQ), whereas others report no significant changes in REE or RQ. The aim here was to reassess the concept of water-induced thermogenesis and fat oxidation in humans, with particular focus on interindividual variability in REE and RQ responses, comparison with a time-control Sham drink, and on the potential impact of gender, body composition and abdominal adiposity.

Subjects/Methods:

REE and RQ were measured in healthy young adults (n=27; body mass index range: 18.5–33.9 kg m⁻²), by ventilated hood indirect calorimetry for at least 30 min before and 130 min after ingesting 500 ml of purified (distilled) water at 21–22 °C or after Sham drinking, in a randomized cross-over design. Body composition and abdominal fat were assessed by bioimpedance techniques.

Results:

Drinking 500 ml of distilled water led to marginal increases in REE (<3% above baseline), independently of gender, but which were not significantly different from Sham drinking. RQ was found to fall after the water drink, independently of gender, but it also diminished to a similar extent in response to sham drinking. Interindividual variability in REE and RQ responses was not associated with body fatness, central adiposity or fat-free mass.

Conclusions:

This study conducted in young men and women varying widely in adiposity, comparing the ingestion of distilled water to Sham drinking, suggests that ingestion of purified water per se does not result in the stimulation of thermogenesis or fat oxidation.

Metabolic response to epigallocatechin-3-gallate in relapsing-remitting multiple sclerosis: a randomized clinical trial

BACKGROUND

Muscle weakness and fatigue are common symptoms in multiple sclerosis (MS). Green tea catechins such as (-)epigallocatechin-3-gallate (EGCG) are known to improve energy metabolism at rest and during exercise.

OBJECTIVE

We tested the hypothesis that EGCG improves energy metabolism and substrate utilization in patients with MS.

DESIGN

Eighteen patients (8 men) with relapsing-remitting MS (expanded disability status scale score <4.5, all receiving glatiramer acetate) participated in this randomized, double-blind, placebo-controlled, crossover trial at a clinical research center. All patients received EGCG (600 mg/d) and placebo over 12 wk (4-wk washout in between). After each intervention, fasting and postprandial energy expenditure (EE), as well as fat oxidation (FAOx) and carbohydrate oxidation (CHOx) rates, were measured either at rest or during 40 min of exercise (0.5 W/kg). At rest, blood samples and microdialysates from adipose tissue and skeletal muscle were also taken.

RESULTS

At rest, postprandial EE and CHOx, as well as adipose tissue perfusion and glucose supply, were significantly lower in men but higher in women receiving EGCG compared with placebo. During exercise, postprandial EE was lower after EGCG than after placebo, indicating an increased working efficiency (men > women). After placebo, exercise EE was mainly fueled by FAOx in both men and women. After EGCG, there was a shift to a higher and more stable CHOx during exercise in men but not in women.

CONCLUSIONS

Our data indicate that EGCG given to patients with MS over 12 wk improves muscle metabolism during moderate exercise to a greater extent in men than in women, possibly because of sex-specific effects on autonomic and endocrine control.

Opportunities for intervention strategies for weight management: global actions on fluid intake patterns

Water is an essential nutrient for all physiological functions and particularly important for thermoregulation. About 60% of our body weight is made of water. Under standard conditions (18-20 °C and moderate activity), water balance is regulated within 0.2 % of body weight over a 24-hour period. Water requirement varies between individuals and according to environmental conditions. Concerning considerations related to obesity, the health impact of fluid intake is commonly overlooked. Fluid intake advices are missing in most of food pyramids offered to the public, and water requirements and hydration challenges remain often neglected. The purpose of this paper is to emphasize and discuss the role of water consumption in the context of other important public health measures for weight management. Attention will be focused on fluid intake patterns and hydration-related questions in the context of global interventions and/or physical activity programs settled in weight management protocols.

Qualitative and/or quantitative drinking water recommendations for pediatric obesity treatment

OBJECTIVE

The qualitative recommendation to 'drink water instead of caloric beverages' may facilitate pediatric obesity treatment by lowering total energy intake. The quantitative recommendation to 'drink enough water to dilute urine' might further facilitate weight loss by increasing fat oxidation via cell hydration-mediated changes in insulin.

METHODS

This 8 week randomized intervention tested whether both qualitative-plus-quantitative (QQ) drinking water recommendations result in more weight loss than the qualitative recommendation alone (Q) in 25 children (9-12y) with body mass index at or above the 85th Percentile, given a reduced glycemic diet and usual physical activity. Random urine osmolality, saliva insulin, and body weight were assessed weekly. Mixed models explored if insulin mediated an effect of urine osmolality on weight loss.

RESULTS

In intention-to-treat analyses, QQ and Q participants did not differ significantly with respect to level of urine osmolality, saliva insulin, or weight loss. Only 4 out of 16 QQ participants complied with instruction to drink enough water to dilute urine, however. In completers analyses, the compliant QQ participants, who diluted urine osmolality from 910 ± 161 mmol/kg at baseline to below 500 mmol/kg over time (8 week mean±SE: 450 ± 67 mmol/kg), had significantly lower saliva insulin over time (8 week mean±SE: 13 ± 8 pmol/l vs. 22 ± 4 pmol/l) and greater weight loss (mean ± SE: -3.3 ± 0.7kg vs. -2.0 ± 0.5 kg) than compliant Q participants (7 out of 9 participants) who maintained elevated urine osmolality over time (8- week mean±SE: 888 ± 41 mmol/kg). Urine osmolality below 500 mmol/kg was significantly associated with weight loss. Change in saliva insulin partially explained the association.

CONCLUSIONS

QQ recommendations may increase weight loss for those able to dilute urine. Work is warranted to pursue cell hydration effects of drinking water for pediatric obesity treatment.

Effect of excessive water intake on body weight, body mass index, body fat, and appetite of overweight female participants

Objective:

Drinking plenty of water is commonly recommended in weight loss regimens; however, very limited scientific evidence is available to justify this. Here we studied the effect of drinking 1.5 L of water, over and above the usual intake on body weight, body mass index (BMI), body fat, and appetite score in overweight female participants.

Materials and Methods:

The study was done on 50 overweight female participants, who were instructed to drink 500 mL of water, three times a day 30 min before breakfast, lunch, and dinner. The 1.5 L water intake was over and above their daily water intake and was continued for 8 consecutive weeks. Body weight, BMI, body fat, and appetite score was measured pre and post-study; and the values were compared by paired t-test using Statistical Packages for Social Sciences (SPSS) version 14.0.1.

Results:

All the parameters tested were lower after 8 weeks: body weight (pre-study 65.86 ± 3.614 kg vs post-study 64.42 ± 3.704 kg; P < 0.01); BMI (pre-study 26.7002 ± 0.9423 vs post-study 26.1224 ± 1.0632; P < 0.01); sum of skinfold thickness (pre-study 79.626 ± 10.385 mm vs post-study 76.578 ± 10.477 mm; P < 0.01); and the appetite score (pre-study 36.880 ± 4.170 vs post-study 34.673 ± 3.845; P < 0.01).

Conclusions:

Our study establishes the role of drinking 1.5 L of excessive water in weight reduction, body fat reduction, and appetite suppression in overweight female participants.

Osmotic homeostasis

Alterations in water homeostasis can disturb cell size and function. Although most cells can internally regulate cell volume in response to osmolar stress, neurons are particularly at risk given a combination of complex cell function and space restriction within the calvarium. Thus, regulating water balance is fundamental to survival. Through specialized neuronal "osmoreceptors" that sense changes in plasma osmolality, vasopressin release and thirst are titrated in order to achieve water balance. Fine-tuning of water absorption occurs along the collecting duct, and depends on unique structural modifications of renal tubular epithelium that confer a wide range of water permeability. In this article, we review the mechanisms that ensure water homeostasis as well as the fundamentals of disorders of water balance.

Beyond the role of dietary protein and amino acids in the prevention of diet-induced obesity

High-protein diets have been shown to prevent the development of diet-induced obesity and can improve associated metabolic disorders in mice. Dietary leucine supplementation can partially mimic this effect. However, the molecular mechanisms triggering these preventive effects remain to be satisfactorily explained. Here we review studies showing a connection between high protein or total amino nitrogen intake and obligatory water intake. High amino nitrogen intake may possibly lower lipid storage, and prevent insulin resistance. Suggestions are made for further systematical studies to explore the relationship between water consumption, satiety, and energy expenditure. Moreover, these examinations should better distinguish between leucine-specific and unspecific effects. Research in this field can provide important information to justify dietary recommendations and strategies in promoting long-term weight loss and may help to reduce health problems associated with the comorbidities of obesity.

Effect of 'water induced thermogenesis' on body weight, body mass index and body composition of overweight subjects

CONTEXT

Drinking lots of water is commonly suggested as a part of weight loss regimens. However, only few systematic studies have addressed this notion. In this study, the effect of drinking 1500 ml of water, over and above the daily water intake on body weight, body mass index (BMI) and body composition of overweight subjects was assessed.

AIM

To evaluate the role of drinking excessive water in weight reduction and body fat reduction of overweight subjects.

SETTINGS AND DESIGN

This study was conducted on 50 overweight girls for eight weeks, during which they were instructed to drink 500 ml of water, three times a day, half an hour before breakfast, lunch and dinner, which was over and above their daily water intake.

MATERIAL AND METHODS

Body weight was measured in kilograms (kgs). BMI was calculated as weight in kilograms, which was divided by the square of height in metres. Body composition score was calculated as a sum of skin fold thickness in millimetres at three different sites, which was measured by using skin fold calipers. Pre and post-study body weight, body mass index and body composition scores were measured.

STATISTICAL ANALYSIS

SPSS, version 14.0.1 and paired t-test were used to find out the statistical significance of the results.

RESULTS

The mean values of the pre-study and post-study body weight, body mass index and body composition scores were 65.86 kg and 64.42 kg, 26.7002 and 26.1224 and 79.626 mm and 76.578 mm respectively. All the three results were highly significant statistically.

CONCLUSIONS

The decrease in body weight, body mass index and body composition scores of overweight subjects at the end of study period establishes the role of water induced thermogenesis in weight reduction of overweight subjects.

Association between water consumption and body weight outcomes: a systematic review

BACKGROUND

Drinking water is often applied as a dietary means for weight loss and overweight/obesity prevention, but no evidence-based recommendation exists for this indication.

OBJECTIVE

We summarized the existing evidence on the association between water consumption and body weight outcomes in adults of any body weight status.

DESIGN

In a systematic review, we retrieved studies from 4 electronic databases (MEDLINE, EMBASE, CINAHL, and COCHRANE), cross-references by PubMed functions and hand-searching, and experts' recommendations. Any type of study including adults aged >18 y that reported the association between daily water consumption and any weight-related outcome, such as body weight, body mass index, or body weight classifications, was eligible.

RESULTS

Of 4963 retrieved records, 11 original studies and 2 systematic reviews were included. In participants dieting for weight loss or maintenance, a randomized controlled trial, a nonrandomized controlled trial, and an observational longitudinal study showed that increased water consumption, in addition to a program for weight loss or maintenance, reduced body weight after 3-12 mo compared with such a program alone. In mixed-weight populations not primarily dieting for weight loss or maintenance, 2 short-term randomized trials showed no effect of water consumption on body weight; 6 cross-sectional studies showed inconsistent results.

CONCLUSIONS

Studies of individuals dieting for weight loss or maintenance suggest a weight-reducing effect of increased water consumption, whereas studies in general mixed-weight populations yielded inconsistent results. The evidence for this association is still low, mostly because of the lack of good-quality studies. This trial was registered at www.crd.york.ac.uk/Prospero as CRD42012002585.

Changes in water and beverage intake and long-term weight changes: results from three prospective cohort studies

OBJECTIVE

To examine the long-term relationship between changes in water and beverage intake and weight change.

SUBJECTS

Prospective cohort studies of 50013 women aged 40-64 years in the Nurses' Health Study (NHS, 1986-2006), 52987 women aged 27-44 years in the NHS II (1991-2007) and 21988 men aged 40-64 years in the Health Professionals Follow-up Study (1986-2006) without obesity and chronic diseases at baseline.

MEASURES

We assessed the association of weight change within each 4-year interval, with changes in beverage intakes and other lifestyle behaviors during the same period. Multivariate linear regression with robust variance and accounting for within-person repeated measures were used to evaluate the association. Results across the three cohorts were pooled by an inverse-variance-weighted meta-analysis.

RESULTS

Participants gained an average of 1.45 kg (5th to 95th percentile: -1.87 to 5.46) within each 4-year period. After controlling for age, baseline body mass index and changes in other lifestyle behaviors (diet, smoking habits, exercise, alcohol, sleep duration, TV watching), each 1 cup per day increment of water intake was inversely associated with weight gain within each 4-year period (-0.13 kg; 95% confidence interval (CI): -0.17 to -0.08). The associations for other beverages were: sugar-sweetened beverages (SSBs) (0.36 kg; 95% CI: 0.24-0.48), fruit juice (0.22 kg; 95% CI: 0.15-0.28), coffee (-0.14 kg; 95% CI: -0.19 to -0.09), tea (-0.03 kg; 95% CI: -0.05 to -0.01), diet beverages (-0.10 kg; 95% CI: -0.14 to -0.06), low-fat milk (0.02 kg; 95% CI: -0.04 to 0.09) and whole milk (0.02 kg; 95% CI: -0.06 to 0.10). We estimated that replacement of 1 serving per day of SSBs by 1 cup per day of water was associated with 0.49 kg (95% CI: 0.32-0.65) less weight gain over each 4-year period, and the replacement estimate of fruit juices by water was 0.35 kg (95% CI: 0.23-0.46). Substitution of SSBs or fruit juices by other beverages (coffee, tea, diet beverages, low-fat and whole milk) were all significantly and inversely associated with weight gain.

CONCLUSION

Our results suggest that increasing water intake in place of SSBs or fruit juices is associated with lower long-term weight gain.

Challenges of linking chronic dehydration and fluid consumption to health outcomes

The purpose of this article is to review the effects of chronic mild dehydration and fluid consumption on specific health outcomes including obesity. The electronic databases PubMed and Google Scholar were searched for relevant literature published from the time of their inception to 2011, with results restricted to studies performed on human subjects and reports in the English language. Key words included the following: dehydration, hypohydration, water intake, fluid intake, disease, and the names of specific disease states. Strength of evidence categories were described for 1) medical conditions associated with chronic dehydration or low daily water intake, and 2) randomized-controlled trials regarding the effects of increased water consumption on caloric intake, weight gain, and satiety. This process determined that urolithiasis is the only disorder that has been consistently associated (i.e., 11 of 13 publications) with chronic low daily water intake. Regarding obesity and type 2 diabetes, evidence suggests that increased water intake may reduce caloric intake for some individuals. Recommendations for future investigations include measuring total fluid intake (water + beverages + water in solid food), conducting randomized-controlled experiments, identifying novel hydration biomarkers, and delineating hydration categories.

The influence of oral water load on energy expenditure and sympatho-vagal balance in obese and normal weight women

INTRODUCTION

Oral water load may increase the energy expenditure (EE) by stimulation of sympathetic dependent thermogenesis. Thus, drinking of water may be helpful in weight reduction. The aim of the study is to assess the influence of water load on energy expenditure and sympathetic activity in obese and normal weight women.

MATERIAL AND METHODS

Forty-five women were included. Energy expenditure was measured twice, in the morning and after oral water load, by the indirect calorimetric method. The heart rate variability parameters low frequency (LF), high frequency (HF), LF/HF index, standard deviation of normal RR intervals (SDNN) and root mean square difference among successive RR normal intervals (rMSSD) were used for the indirect assessment of the sympatho-vagal balance.

RESULTS

Resting energy expenditure (REE) was significantly higher in obese than in normal weight women (1529 ±396 kcal/day vs. 1198 ±373 kcal/day; p = 0.02). In both study groups after water load EE increased significantly (by 20% and by 12%, corresponding to 8.6 kcal/h and 5.2 kcal/h respectively), while, LF/HF index increased simultaneously. The increase of energy expenditure (EE) did not exceed the energetic cost of water heating, from room to body temperature - 15 kcal/1000 ml. There was no correlation between changes of energy expenditure (EE) and heart rate variability (HRV) parameters.

CONCLUSIONS

The increase of EE induced by water load is mostly related to the heating of the consumed water to body temperature. The assessment of autonomic balance by means of standard HRV indices had been found insufficient for detection of actually operating mechanisms.

Liver afferents contribute to water drinking-induced sympathetic activation in human subjects: a clinical trial

Water drinking acutely increases sympathetic activity in human subjects. In animals, the response appears to be mediated through transient receptor potential channel TRPV4 activation on osmosensitive hepatic spinal afferents, described as osmopressor response. We hypothesized that hepatic denervation attenuates water drinking-induced sympathetic activation. We studied 20 liver transplant recipients (44±2.6 years, 1.2±0.1 years post transplant) as model of hepatic denervation and 20 kidney transplant recipients (43±2.6 years, 0.8±0.1 years post transplant) as immunosuppressive drug matched control group. Before and after 500 ml water ingestion, we obtained venous blood samples for catecholamine analysis. We also monitored brachial and finger blood pressure, ECG, and thoracic bioimpedance. Plasma norepinephrine concentration had changed by 0.01±0.07 nmol/l in liver and by 0.21±0.07 nmol/l in kidney transplant recipients (p<0.05 between groups) after 30–40 minutes of water drinking. While blood pressure and systemic vascular resistance increased in both groups, the responses tended to be attenuated in liver transplant recipients. Our findings support the idea that osmosensitive hepatic afferents are involved in water drinking-induced sympathetic activation in human subjects.

Deletion of the mammalian INDY homolog mimics aspects of dietary restriction and protects against adiposity and insulin resistance in mice

Reduced expression of the Indy (I'm Not Dead, Yet) gene in D. melanogaster and its homolog in C. elegans prolongs life span and in D. melanogaster augments mitochondrial biogenesis in a manner akin to caloric restriction. However, the cellular mechanism by which Indy does this is unknown. Here, we report on the knockout mouse model of the mammalian Indy (mIndy) homolog, SLC13A5. Deletion of mIndy in mice (mINDY(-/-) mice) reduces hepatocellular ATP/ADP ratio, activates hepatic AMPK, induces PGC-1α, inhibits ACC-2, and reduces SREBP-1c levels. This signaling network promotes hepatic mitochondrial biogenesis, lipid oxidation, and energy expenditure and attenuates hepatic de novo lipogenesis. Together, these traits protect mINDY(-/-) mice from the adiposity and insulin resistance that evolve with high-fat feeding and aging. Our studies demonstrate a profound effect of mIndy on mammalian energy metabolism and suggest that mINDY might be a therapeutic target for the treatment of obesity and type 2 diabetes.

Hydration and Health

Daily adequate water intake to maintain euhydration is arguably the most important nutrient requirement for humans. Within a margin of error, the body regulates the maintenance of body fluid balance and especially that of the plasma volume, through mechanisms that stimulate thirst and/or modify the rate of urine production. However, there are circumstances such as with excessive sweating during exercise in the heat, osmotic diarrhea, or excessive fluid consumption, or water intoxication where normal mechanisms of regulation may be inadequate to compensate for acute changes in hydration status and result in life threatening consequences. Health and onset of disease may be affected by the chronic hydration state of individual. The risks of colorectal cancer, nephrolithiasis in those with a history of kidney stones, and bladder cancer may be reduced by more frequent water consumption. Recent research suggests that appropriate timing of water intake around meal occasions may help reduce energy intake and contribute to maintenance of body weight in overweight individuals. Definitive benefits of hydration on cardiovascular and oral health and general immune system function remain to be determined. It is also unclear whether the health benefits of water and fluid ingestion are a function of the process of frequent fluid intake or the maintenance of a potentially expanded state of hydration.