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Water-Induced Thermogenesis Reconsidered: The Effects of Osmolality and Water Temperature on Energy Expenditure after Drinking

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A recent study reported that drinking 500 ml of water causes a 30% increase in metabolic rate. If verified, this previously unrecognized thermogenic property of water would have important implications for weight-loss programs. However, the concept of a thermogenic effect of water is controversial because other studies have found that water drinking does not increase energy expenditure. The objective of the study was to test whether water drinking has a thermogenic effect in humans and, furthermore, determine whether the response is influenced by osmolality or by water temperature. This was a randomized, crossover design. The study was conducted at a university physiology laboratory. Participants included healthy young volunteer subjects. Intervention included drinking 7.5 ml/kg body weight (approximately 518 ml) of distilled water or 0.9% saline or 7% sucrose solution (positive control) on different days. In a subgroup of subjects, responses to cold water (3 C) were tested. Resting energy expenditure, assessed by indirect calorimetry for 30 min before and 90 min after the drinks, was measured. Energy expenditure did not increase after drinking either distilled water (P = 0.34) or 0.9% saline (P = 0.33). Drinking the 7% sucrose solution significantly increased energy expenditure (P < 0.0001). Drinking water that had been cooled to 3 C caused a small increase in energy expenditure of 4.5% over 60 min (P < 0.01). Drinking distilled water at room temperature did not increase energy expenditure. Cooling the water before drinking only stimulated a small thermogenic response, well below the theoretical energy cost of warming the water to body temperature. These results cast doubt on water as a thermogenic agent for the management of obesity.
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Water-Induced Thermogenesis Reconsidered: The Effects
of Osmolality and Water Temperature on Energy
Expenditure after Drinking
Clive M. Brown, Abdul G. Dulloo, and Jean-Pierre Montani
Department of Medicine, Division of Physiology, University of Fribourg, 1700 Fribourg, Switzerland
Context: A recent study reported that drinking 500 ml of water
causes a 30% increase in metabolic rate. If verified, this previously
unrecognized thermogenic property of water would have important
implications for weight-loss programs. However, the concept of a
thermogenic effect of water is controversial because other studies
have found that water drinking does not increase energy expenditure.
Objective: The objective of the study was to test whether water
drinking has a thermogenic effect in humans and, furthermore, de-
termine whether the response is influenced by osmolality or by water
temperature.
Design: This was a randomized, crossover design.
Setting: The study was conducted at a university physiology laboratory.
Participants: Participants included healthy young volunteer
subjects.
Intervention: Intervention included drinking 7.5 ml/kg body weight
(518 ml) of distilled water or 0.9% saline or 7% sucrose solution
(positive control) on different days. In a subgroup of subjects, re-
sponses to cold water (3 C) were tested.
Main Outcome Measure: Resting energy expenditure, assessed by
indirect calorimetry for 30 min before and 90 min after the drinks, was
measured.
Results: Energy expenditure did not increase after drinking either
distilled water (P 0.34) or 0.9% saline (P 0.33). Drinking the
7% sucrose solution significantly increased energy expenditure
(P 0.0001). Drinking water that had been cooled to 3 C caused
a small increase in energy expenditure of 4.5% over 60 min (P
0.01).
Conclusions: Drinking distilled water at room temperature did
not increase energy expenditure. Cooling the water before drinking
only stimulated a small thermogenic response, well below the the-
oretical energy cost of warming the water to body temperature.
These results cast doubt on water as a thermogenic agent for
the management of obesity. (J Clin Endocrinol Metab 91:
3598 –3602, 2006)
T
HE HIGH PREVALENCE of overweight and obesity has
led to the search for compounds that can increase en-
ergy expenditure and fat oxidation, thereby promoting
weight loss. Because thermogenesis is partly regulated by
sympathetic activity, substances that interact with the sym-
pathetic nervous system can be considered as potential
agents for weight reduction (1). Sympathomimetic com-
pounds such as ephedrine are effective at increasing ther-
mogenesis (2) but can have undesirable side effects (3). Safe,
preferably nonpharmacological substances that can stimu-
late thermogenesis without causing side effects are therefore
sought. A surprising candidate for a thermogenic agent is
one of the most essential of all substances required for life:
water. Drinking half a liter of water increases activity of the
sympathetic nervous system as measured by enhanced
plasma norepinephrine levels (4) and muscle sympathetic
nerve activity (5). Boschmann et al. (6) hypothesized that the
sympathetic activation after water drinking might stimulate
thermogenesis. They reported that drinking 500 ml of water
increased resting energy expenditure by 30%. The response
started within 10 min of drinking the water, peaked at 30 40
min, and was sustained for more than an hour (6). The
water-induced thermogenesis was attributed to sympathetic
nervous system activation because ingestion of a
-adreno-
receptor blocker before drinking almost completely abol-
ished the response. Drinking water that had been heated to
37 C attenuated the thermogenic response by 40%, which led
to the suggestion that water-induced thermogenesis could be
partly attributed to the energy cost of warming the water to
body temperature (6). The authors extrapolated that increas-
ing daily water intake by 1.5 liters would augment energy
expenditure by approximately 200 kJ/d (6). If confirmed,
water-induced thermogenesis would have important impli-
cations for weight control programs. However, the concept
of water-induced thermogenesis is controversial. Several
studies in humans (7–16) have reported that water drinking
has little or no effect on resting energy expenditure (Table 1).
We therefore undertook the present study to further in-
vestigate the concept of water-induced thermogenesis. To
eliminate the possibility that dissolved impurities or other
substances in tap or mineral water might contribute to ther-
mogenesis, we used distilled water. On the basis that osmo-
lality might have a role in water-induced thermogenesis, we
also tested responses to physiological (0.9%) saline. As a
positive control, thermogenic responses were measured after
ingestion of the same volume of a 7% sucrose solution. Fi-
First Published Online July 5, 2006
Abbreviations: BMI, Body mass index; RQ, respiratory quotient;
VCO
2
, carbon dioxide production; VO
2
, oxygen consumption.
JCEM is published monthly by The Endocrine Society (http://www.
endo-society.org), the foremost professional society serving the en-
docrine community.
0021-972X/06/$15.00/0 The Journal of Clinical Endocrinology & Metabolism 91(9):3598–3602
Printed in U.S.A. Copyright © 2006 by The Endocrine Society
doi: 10.1210/jc.2006-0407
3598
nally, considering the suggestion that part of water-induced
thermogenesis might be attributed to the energy required to
warm the water to body temperature, we tested whether
ingestion of cold water would augment the thermic response.
Subjects and Methods
Subjects
Responses to ingestion of distilled water, 0.9% saline, and 7% sucrose
were measured in eight healthy volunteer subjects [six males, two fe-
males; aged 25 1 yr; height 176 3 cm; weight 69 2 kg; body mass
index (BMI) 22.5 0.7 kg/m
2
]. Statistical analysis showed that this
number of subjects was sufficient to detect, at a significance level (alpha)
of 0.05 and power (1-beta) of 0.96, a change in resting energy expenditure
of 6% with a sd of the response of 5%. Time-control experiments were
performed in five subjects (three males, two females; aged 26 2 yr;
height 176 3 cm; weight 64 3 kg; BMI 20.8 0.7 kg/m
2
). In six healthy
subjects (five males, one female; age 27 1 yr; height 179 3 cm; weight
66 3 kg; BMI 20.8 0.6 kg/m
2
), we assessed responses to ingestion of
cold water (3 C). None of the subjects had any diseases or were taking
medications. The subjects were requested to avoid doing physical exercise,
refrain from caffeine consumption for at least 24 h, and have nothing to eat
for 12 h and nothing to drink for 2 h before the experiments. Written
informed consent was obtained from each subject according to the Decla-
ration of Helsinki. The study protocol was approved by the institutional
ethics committee.
Protocol
All measurements were performed in the morning, starting at 0830
0930 h, in a temperature-controlled (21 C) quiet room with the subjects
in a comfortable seated position.
Ingestion of distilled water, 0.9% saline, and 7% sucrose. The subjects at-
tended three experimental sessions according to a randomized crossover
design. Respiratory gas exchange was measured by indirect calorimetry
using an open-circuit ventilated hood system (Deltatrac monitor; Datex,
Helsinki, Finland). Resting energy expenditure and respiratory quotient
(RQ) were derived from the rates of oxygen consumption (VO
2
) and
carbon dioxide production (VCO
2
) using the Weir equation (17). The
precision of the gas analyzers, the calibration procedure, and the accu-
racy of the entire ventilated-hood system were regularly determined by
ethanol combustion tests lasting between 2 and 4 h. These ethanol tests
yield values for RQ of 0.67, with a coefficient of variation less than 2%
and differences between calculated and measured energy expenditure
of less than 3%. After an initial resting period of 30 40 min to allow gas
exchange values to reach a steady state, resting energy expenditure was
measured over 30 min. Then subjects ingested 7.5 ml/kg body weight
(mean volume 518 16 ml) of distilled water, 0.9% saline, or a 7%
sucrose solution over 3 min. The drinks were served at room temper-
ature. Gas exchange measurements were continued for a further 90 min
after the drink. Values were recorded every minute and then averaged
over 10-min intervals.
Time-control experiment. In five volunteers we tested the effects of a sham
drink. After resting energy expenditure was recorded over a 30-min
period, the subjects raised a vessel containing water (7.5 ml/kg body
weight) to their lips but did not ingest any of the water. Resting energy
expenditure was recorded for a further 90 min after the sham drink.
Ingestion of cold water. In a subgroup of six subjects, we tested the effects
of ingesting distilled water (7.5 ml/kg body weight, mean volume 4.95
ml) that had been cooled to 3 C.
Statistical analysis
All data are given as means sem. Responses to the distilled water,
0.9% saline, and 7% sucrose drinks were tested by ANOVA for repeated
measures. The postdrink values at 10-min time intervals were compared
with values recorded during the 30-min baseline period using Dunnett’s
test for multiple comparisons. Total changes in energy expenditure
(areas under the curve) after the three drinks were compared by
ANOVA for repeated measures with Tukey’s post hoc test to compare
pairs of drinks. Energy expenditure after ingestion of cold water was
compared with the corresponding baseline value by a paired t test. The
statistics were performed using statistical software (InStat version 3.01;
GraphPad Software, San Diego, CA). The level of statistical significance
was set at P 0.05.
Results
Responses to distilled water, 0.9% saline, and 7% sucrose
Resting values of VO
2
, VCO
2
, resting energy expenditure,
and RQ as recorded over 30 min before ingestion of each of
the drinks were similar and are shown in Table 2. The time
courses of the responses to the three drinks are shown in Fig.
1. Ingestion of distilled water did not significantly affect VO
2
(P 0.20), VCO
2
(P 0.60), resting energy expenditure (P
0.34), or RQ (P 0.14). Similarly, ingestion of 0.9% saline had
no significant effects on VO
2
(P 0.30), VCO
2
(P 0.15),
resting energy expenditure (P 0.33), or RQ (P 0.14). In
contrast, ingestion of 7% sucrose resulted in a significant and
sustained increase in VO
2
, VCO
2
, resting energy expendi
-
TABLE 1. Summary of several published studies measuring acute changes in energy expenditure after water drinking in humans
Study
Year of
publication
Water volume
No. of
subjects
Calorimetry
method
Reported increase in
energy expenditure?
Boschmann et al. (6) 2003 500 ml 14 Whole room 30% increase after 60 min
Brundin and Wahren (7) 1993 375 ml 7 Ventilated hood 2% increase over 2 h
De Jonge et al. (8) 1991 Not stated
a
9 Ventilated hood No
Dulloo and Miller (9) 1986 200 ml 8 Douglas bag No
Felig et al. (10) 1983 400 ml 3 Ventilated hood No
Gougeon et al. (11) 2005 750 ml 2 Ventilated hood No
Komatsu et al. (12) 2003 300 ml 8 Douglas bag 2.7% increase over 2 h
LeBlanc et al. (13) 1984 600 ml 8 Pneumotachograph No
Li et al. (14) 1999 280 ml 19 Ventilated hood No
Paolisso et al. (15) 1997 Not stated 8 Ventilated hood No
Sharief and Macdonald (16) 1982 4 ml/kg ideal body weight
(average 292 ml)
6 Ventilated hood No
a
But at least 410 ml.
TABLE 2. Resting values of gaseous exchange parameters and
resting energy expenditure recorded over 30 min immediately
before ingestion of the water, saline, and sucrose drinks
Water Saline Sucrose
VO
2
(ml/min)
224 14 218 13 228 14
VCO
2
(ml/min)
199 13 190 11 193 12
Resting energy expenditure
(kJ/min)
4.53 0.29 4.40 0.26 4.58 0.28
RQ 0.89 0.02 0.87 0.02 0.85 0.02
Brown et al. Water-Induced Thermogenesis Reconsidered J Clin Endocrinol Metab, September 2006, 91(9):3598 –3602 3599
ture, and RQ (all P 0.0001). The average 90-min increase
in resting energy expenditure (area under the curve) after the
sucrose drink was 33 4 kJ, compared with 2 6 kJ after
the distilled water drink and 7 5 kJ after the saline drink
(ANOVA, P 0.0002; Tukey post hoc test, water vs. saline, P
0.05; water vs. sucrose, P 0.001; saline vs. sucrose, P 0.01).
Individual responses to ingestion of the water and sucrose
drinks are compared in Fig. 2.
Time-control experiment
Responses to ingestion of the sham drink are included in
Fig. 1. The coefficient of variation for resting energy expen-
diture over the entire 2-h recording period was 2.3% (1.9%
before the sham drink and 2.4% after the sham drink). By
comparison, for the water drink, the coefficient of variation
for resting energy expenditure was 3.0% over the 2-h re-
cording period (2.0% before the drink and 2.7% after the
drink).
Responses to cold water
Drinking distilled water that had been cooled to3Cin-
creased resting energy expenditure in all six subjects (Fig. 3),
from 4.48 0.24 to 4.69 0.23 kJ/min (P 0.0068) over 60
min. The total increase in resting energy expenditure (area
under the curve) after 3 C water ingestion was 13 3 kJ after
60 min and 15 3 kJ after 90 min.
Discussion
It was reported that drinking half a liter of water at room
temperature increased resting energy expenditure by 30%
after an hour (6). This previously unrecognized thermogenic
property of water was suggested as a potential means for
increasing energy expenditure in the treatment of obese and
FIG. 1. Changes in VO
2
(A), VCO
2
(B), resting energy
expenditure (REE) (C), and RQ (D) after drinking
distilled water, 0.9% saline, or a 7% sucrose solution.
Responses to a sham drink are also plotted. The
drinks were ingested at time 0 min. Data points rep-
resent the mean value over the preceding 10 min (*,
P 0.05; **, P 0.01).
FIG. 2. Integrated changes in resting energy expenditure (REE) over
90 min in individual subjects after drinking water or a 7% sucrose
solution (**, P 0.01).
3600 J Clin Endocrinol Metab, September 2006, 91(9):3598 –3602 Brown et al. Water-Induced Thermogenesis Reconsidered
overweight individuals (6). The current study was designed
to reassess water-induced thermogenesis and investigate
whether osmolality or water temperature might influence
energy expenditure after drinking. Our results are, however,
inconsistent with the concept of water-induced thermogen-
esis. Resting energy expenditure remained unchanged after
drinking distilled water or a 0.9% saline solution. Drinking
water that had been cooled to 3 C increased resting energy
expenditure by only about 5%. In contrast, ingestion of a 7%
sucrose solution increased resting energy expenditure by 33
kJ over 90 min. This amounts to about 5% of the energy
content of the sucrose and is in line with the dietary-induced
thermogenesis reported elsewhere after carbohydrate inges-
tion (7, 14).
Boschmann et al. (6) reported that drinking water that had
been warmed to 37 C reduced the postdrink increase in
energy expenditure by 40%. The extent of this attenuation in
water-induced thermogenesis closely matched the calculated
energy required to heat the water from room temperature to
body temperature (about 30 kJ for 500 ml) (6). On that basis,
drinking cold water should augment the thermogenic effect.
Indeed, we found that drinking distilled water that had been
cooled to 3 C slightly increased resting energy expenditure
by an average of 15 kJ over 90 min. However, this is sub-
stantially lower than the calculated energy required to heat
the water from 3 to 37 C (495 ml 34 C 16830 cal 70 kJ),
suggesting that most of the energy required for warming the
water to body temperature is more likely to be met by a
reduction in body heat loss, probably by the peripheral va-
soconstriction that occurs after water drinking (5).
The 30% increase in energy expenditure after water drink-
ing reported by Boschmann et al. (6) is impressive, but it is
not supported by previously published studies (7–16) or the
results of the current study. What could be the explanation
for the apparent water-induced thermogenesis? One clue
could be in the fact that Boschmann et al. (6) measured energy
expenditure by whole-room indirect calorimetery, as op-
posed to the ventilated hood or mouthpiece techniques that
we and others (7–16) have used. Ventilated hood and mouth-
piece apparatus have a small dead space, thereby permitting
rapid attainment of steady-state gas concentrations. In con-
trast, whole-room calorimeters may require1hormore to
attain steady-state conditions because of their large size in
relation to ventilation rate (18) and are therefore less suitable
for acute measurements. Boschmann et al. (6) used a run-in
period of only 15 min before starting to measure resting
energy expenditure. It is possible that their data reported
from 30 min later, after water drinking, might be a conse-
quence of a slow response time of the whole-room calorim-
eter and simply reflect earlier activities within the chamber.
Unfortunately, Boschmann et al. (6) did not provide any
information about the size of their chamber or the time re-
quired to reach a steady state.
Water-induced thermogenesis might also result from sub-
stances dissolved in the water. Boschmann et al. (6) did not
state in their paper whether they used tap water, bottled
water, or distilled water. Tap water and bottled water contain
a number of dissolved electrolytes and impurities that could
potentially stimulate a thermogenic effect. In the current
study, we excluded this possibility by using distilled water.
Various studies have indicated that drinking half a liter of
water increases the activity of the sympathetic nervous sys-
tem (4, 5). The hypothesis that water drinking might also
stimulate the metabolism therefore seems reasonable. It is,
however, important to note that sympathetic activation does
not uniformly affect all physiological functions. Sympathetic
nervous system activity to several organs (such as heart,
liver, kidneys, and pancreas) is increased in response to diet,
but it is uncertain as to whether they contribute to dietary-
induced thermogenesis (19). An increase in sympathetic ac-
tivity to skeletal muscle has been reported after water drink-
ing (5). Yet in humans, infusion of norepinephrine does not
result in a detectable increase in thermogenesis in forearm
skeletal muscle (20). Therefore, sympathetic activation ob-
served after water drinking (particularly to skeletal muscle)
might not necessarily lead to an increase in metabolic rate.
Instead, the increase in sympathetic neural activity after wa-
ter drinking is accompanied by peripheral vasoconstriction
and a reduction in limb blood flow (5).
The confirmation of water-induced thermogenesis would
have important public health implications, not least because
water drinking might be useful as a safe, cheap, and non-
pharmacological method of reducing weight. Using an ex-
perimental setup capable of rapidly detecting small changes
in energy expenditure, we were unable to find a thermogenic
effect of distilled water at room temperature. Consequently,
our results cast doubt on a role for water as a thermogenic
agent in the management of obesity.
Acknowledgments
Received February 22, 2006. Accepted June 27, 2006.
Address all correspondence and requests for reprints to: Dr. Clive M.
Brown, Department of Medicine, Division of Physiology, University of
Fribourg, Rue du Muse´e 5, 1700 Fribourg, Switzerland. E-mail:
clivemartin.brown@unifr.ch.
This work was supported by grants from the Swiss Foundation for
Nutrition Research and the Swiss Heart Foundation.
Author disclosure summary: C.M.B., A.G.D., and J.-P.M. have noth-
ing to declare.
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3602 J Clin Endocrinol Metab, September 2006, 91(9):3598 –3602 Brown et al. Water-Induced Thermogenesis Reconsidered
... Therefore, safe, preferably non-pharmacological substances that can stimulate thermogenesis without causing side effects come to the fore. A surprising candidate for a thermogenic agent is water, one of the most important of all essential substances for life [27]. On average, the consumption of 500 mL water significantly and rapidly increases sympathetic activity with increased plasma norepinephrine levels [28]. ...
... However, these findings could not be replicated by the different study groups. In another study by Brown et al. [27] to test whether water consumption has a thermogenic effect in humans and also to determine whether this is affected by osmolality or water temperature, individuals were given 7.5 mL/kg body weight of distilled water or 0.9% saline or 7% sucrose solutions were given on different days. REE as assessed by indirect calorimetry was measured 30 min before and 90 min after the drinks. ...
... For 90 min, 7% sucrose solution REE increased 33 kJ, and water consumption chilled to 3 °C increased 15 kJ. As a result, the consumption of distilled water at room temperature did not increase energy consumption, while cooling the water before drinking caused only a minor thermogenic effect [27]. It is thought that this difference between studies may be due to differences in REE measurement techniques or other methodological issues, because water-induced thermogenesis can also be caused by substances dissolved in water. ...
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... Although the exact mechanism of these effects requires further study, one hypothesis could be the activation of gastrointestinal thermoreceptors (El Ouazzani, 1984). This is because the body regulates the temperature of fluids or nutrients immediately after receiving them, leading to increased calorie burning (Hrudey et al. 2006;Brown et al. 2006). Cold receptor activation of the gastrointestinal tract also inhibits vasopressin release from the paraventricular nucleus of the hypothalamus (Salata et al. 1987). ...
... In addition, drinking cold water can disrupt the natural process of absorbing nutrients from the food consumed in the digestive tract. It is possible that by drinking cold water, the bloodstream from the digestive tract is focused on regulating body temperature (Webber et al. 1980;Brown et al. 2006) which can cause dehydration of the body in the form of mucus (Wang et al. 2012). Moreover, it was reported that cold water can affect thyroid function and metabolism (Amri, 2018). ...
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... While drinking cold water has been widely promoted as a weight loss strategy on the basis that it induces the body to burn calories to heat up the water for the maintenance of a homeostatic internal body temperature [32], in our study, participants who drank preferentially cold water was associated with a higher BMI and WC. This suggests that the effect of cold water intake in boosting energy expenditure may not be sufficient enough to make a meaningful difference in body weight (about 7 kcal over 90minutes when drinking 1L of water at room temperature) [33] and other adverse effects associated with cold water intake, such as restriction of digestion and blood flow due to contraction of muscle and blood vessels and weakened immunity, may outweigh [34][35][36]. ...
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Water intake has been suggested to be associated with weight control, but evidence for optimal water intake in terms of amount, timing, and temperature is sparse. Additionally, genetic predisposition to obesity, which affects satiety and energy expenditure, might interact with water intake in regulating individual adiposity risk. We conducted a cross-sectional study recruiting 172 Korean adults. Information on water intake and lifestyle factors was collected through self-reported questionnaires, and height, weight, and waist circumference (WC) were measured by researchers. The oral buccal swab was performed for genotyping of FTO rs9939609, MC4R rs17782313, BDNF rs6265 and genetic risk of obesity was calculated. Linear regression was performed to estimate mean difference in body mass index (BMI) and WC by water intake and its 95% confidence interval (95% CI). As a sensitivity analysis, logistic regression was performed to estimate odds ratio (OR) of obesity/overweight (BMI of ≥23kg/m²; WC of ≥90cm for men and of ≥80cm for women) and its 95% CI. Drinking >1L/day was significantly associated with higher BMI (mean difference: 0.90, 95% CI 0.09, 1.72) and WC (mean difference: 3.01, 95% CI 0.62, 5.41) compared with drinking ≤1L/day. Independent of total water intake, drinking before bedtime was significantly associated with lower BMI (mean difference: -0.98, 95% CI -1.91, -0.05). The results remained consistent when continuous BMI and WC were analyzed as categorical outcomes. By perceived temperature, drinking >1L/day of cold water was associated with higher BMI and WC compared with drinking ≤1L/day of water at room-temperature. By genetic predisposition to obesity, a positive association between water intake and WC was confined to participants with low genetic risk of obesity (P interaction = 0.04). In conclusion, amount, timing, and perceived temperature of water intake may be associated with adiposity risk and the associations might vary according to genetic predisposition to obesity.
... For instance, drinking water before a meal induces gastric distension, which reduces appetite and increases satiety, subsequently leading to lower energy intake [11][12][13]. Additionally, water intake has been suggested to influence plasma norepinephrine levels, which promote sympathetic activities such as stimulating thermogenesis, thereby increasing energy expenditure [14,15]. ...
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Background: Water consumption is believed to be a key factor in weight management strategies, yet the existing literature on the subject yields inconsistent findings. To systematically assess the scientific evidence regarding the effect of water intake on adiposity, we conducted a systematic review and meta-analysis of randomized controlled trials (RCTs) among overweight and obese populations. Methods: PubMed and Embase were searched for relevant articles published up to December 2023. The summary weighted mean difference (WMD) and 95% confidence interval (CI) were estimated using the DerSimonian–Laird random-effects model. Results: In this meta-analysis of eight RCTs, interventions to promote water intake or to substitute water for other beverages as compared to the control group resulted in a summary WMD of −0.33 kg (95% CI = −1.75–1.08, I² = 78%) for body weight, −0.23 kg/m² (95% CI = −0.55–0.09, I² = 0%) for body mass index (BMI), and 0.05 cm (95% CI = −1.20–1.30, I² = 40%) for waist circumference (WC). Among RCTs substituting water for artificially sweetened beverages, summary WMD was 1.82 kg (95% CI = 0.97–2.67, I² = 0%) for body weight and 1.23 cm (95% CI = −0.03–2.48, I² = 0%) for WC. Conversely, among RCTs substituting water for sugar-sweetened beverages, summary WMD was −0.81 kg (95% CI = −1.66–0.03, I² = 2%) for body weight and −0.96 cm (95% CI = −2.06–0.13, I² = 0%) for WC. Conclusions: In conclusion, water intake may not significantly impact adiposity among overweight and obese individuals. However, replacing sugar-sweetened beverages with water might offer a modest benefit in inducing weight loss.
... Skin blood flux DF Dominant frequency EDF European data format RMSSD Root mean square of successive differences ST 36 Zusanli acupoint ECG Electrocardiogram EGG Electrogastrogram HRV Heart rate variability TCM Traditional Chinese Medicine Fig Figure SD Standard deviation SE Standard error ANOVA Analysis of variance Although people prefer to drink cold water during endurance exercise 1 , few reports have studied the effects of drinking water of temperatures in healthy humans [2][3][4] . Studies about the effect of water temperature on blood flux are especially scarce. ...
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Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, there is still a lack of relevant research on whether there are left and right differences in these SkBF change. In the current study, a total of 60 subjects were recruited. Skin blood perfusion of the bilateral lower extremities was recorded simultaneously before and after drinking saline of different temperatures saline by using Laser Doppler flowmetry (LDF). The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed. The results indicated that after drinking saline, the laterality index of SkBF at the lower extremities was different and the laterality index changes of SkBF were mainly reflected in the frequency interval V (0.4–1.6 Hz). There was a weak negative correlation between the laterality index of endothelial NO-dependent component and change rate of root mean square of successive differences (RMSSD) after drinking 4 °C saline. However, after drinking 30 °C saline, there was a weak positive correlation between neurogenic component and RMSSD The distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality.
... Tis family of cardiac natriuretic [52,53]. Another feasible mechanism is that increased water intake (as a part of healthy beverages) drives thermogenesis [54][55][56][57] that also would results to a reduction in weight gain. ...
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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.
... Although people prefer to drink cold water [1], few reports have studied the effects of water temperature on healthy humans [2][3][4]. Especially, studies about the effect of water temperature on blood ux are scarce. Scientists have suggested that the water effect does not depend on gastric distension, but on the water osmolality, which could cause an autonomic cardiovascular response in humans through osmotic sensing nerve bers in the intestinal or portal circulation [5,6]. ...
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Background: Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, the distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality. The aim of this study was to analyze the laterality of skin blood flux after drinking saline (0.9%) at different temperatures by monitoring blood flux in the bilateral lower extremities. Methods: A total of 60 subjects were recruited for this study, and all subjects completed all measurements. Subjects were randomly divided into a 4 °C group, 10 °C group and 30 °C group. For every subject, skin blood perfusion of bilateral Zusanli acupoints (ST 36) was recorded simultaneously before and after drinking 500 ml of 0.9% saline using a PeriFlux System 5000. The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed. Results: The results indicated that after drinking saline at different temperatures, the laterality index of skin blood flux at the lower extremities was different. Drinking 30 °C saline can increase the laterality index of the lower extremities. The results of wavelet analysis showed that the laterality index changes of skin blood flux were mainly reflected in the frequency interval V (0.4-1.6 Hz). Stimulation at 4 °C and 10 °C resulted in a decrease in the dominant frequency (DF) of the electrogastrogram and an increased root mean square of successive differences (RMSSD) of the RR interval. There was a weak negative correlation between the laterality index of frequency interval I or II and root mean square of successive differences. Conclusion: There was laterality of blood perfusion in the lower extremities after drinking saline at different temperatures.
... Although humans prefer to drink water at a temperature below standard room temperature 1 , studies about the effect of water temperature on blood ux are scarce. Only a few reports have studied the effects of water temperature on healthy humans [2][3][4] . Scientists have suggested that the water effect does not depend on gastric distension, but on the water osmolality, which could cause an autonomic cardiovascular response in humans through osmotic sensing nerve bers in the intestinal or portal circulation 5,6 . ...
Preprint
Full-text available
Background: Skin blood flux (SkBF) changes caused by drinking cold water are generally associated with vagal tone and osmotic factors in the digestive system. However, the distribution and regulation of bilateral blood flow are not symmetrical but exhibit a certain laterality. The aim of this study was to analyze the laterality of SkBF after drinking saline (0.9%) at different temperatures by monitoring blood flux in the bilateral lower extremities. Methods: A total of 60 subjects were recruited for this study, and all subjects completed all measurements. Subjects were randomly divided into a 4 °C group, 10 °C group and 30 °C group. For every subject, skin blood perfusion of bilateral Zusanli acupoints (ST 36) was recorded simultaneously before and after drinking 500 ml of 0.9% saline using a PeriFlux System 5000. The electrogastrogram (EGG) was also monitored, and the dominant frequency of the EGG and heart rate variability were analyzed. Results: The results indicated that after drinking saline at different temperatures, the laterality index of SkBF at the lower extremities was different. Drinking 30 °C saline can increase the laterality index of the lower extremities. Stimulation at 4 °C and 10 °C resulted in a decrease in the DF of the EGG and an increased RMSSD of the RR interval. Although this laterality is mainly contributed to by frequency interval V, there was a weak negative correlation between the laterality index of frequency interval I or II and RMSSD. Conclusion: There was laterality of blood perfusion in the lower extremities after drinking saline at different temperatures.
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