All the content published in our website is fact checked to validate its accuracy. Visit our guidelines web page to learn more about our strict processes regarding how we review our content's sources: reliable and reputable journals, media websites, universities, colleges, organizations, and professionals. Our articles are based on scientific evidence, and the references are included in its footnotes, which are clickable links to sound scientific papers.
First published: 11.Oct.2018
Overview
Does water promote weight loss?
Several studies have shown that there is a positive correlation between drinking more water than one usually drinks, and weight loss.
In other words: drink more water, and you will very likely lose weight.
The biochemical reason for this weight loss is not yet clearly understood. Furthermore, some studies have reported no weight loss at all.
In this article, we will look into the scientific evidence and discuss some of the possible mechanisms that cause weight loss when hydration is increased.
In 2015, a team led by Dr. Helen Parretti (1) studied a group of 84 obese adults. They gave them advice on how to improve their diet and increase physical activity.
The subjects were split into two groups: one of them had to drink 500 ml (half a quart or 17 fl. oz) of water half an hour before eating their main meals; the other group (control) had to imagine that they had a full stomach before eating.
Study's Outcome
After 12 weeks those who drank water before their meals lost an extra 2.87 lb (1.3 kg) compared to the control group.
Those who drank water before all three main meals lost 9.48 lb (4.3 kg) while those who only had water before one main meal, or not at all, only lost 1.76 lb (0.8 kg).
Take-home point
If you are an overweight adult and drink one-half quart of water before each of your main meals, you could shed some body weight.
A Contradicting Study
In a more limited study, (McKay 2018) (2) studied 49 participants who consumed either one, two, or three 500 ml bottles (just over a pint) of water during the morning and then measured their caloric intake and hunger at lunchtime.
They found that only "normal" weight subjects ate less at lunch (with a lower caloric intake); obese or overweight participants were not affected by drinking water before their meal and ate the same quantity as usual.
Perhaps the limited scope (in duration and intensity - they only drank water before one meal) of this study is the reason for its outcome that disputes Parretti's findings.
Increased Hydration works for those who are Dieting
Muckelbauer (2013) (3) conducted a systematic review of scholarly articles about the link between water consumption and weight loss; the team concluded that "Studies of individuals dieting for weight loss or maintenance suggest a weight-reducing effect of increased water consumption".
In other words, drinking water if you are dieting does help you lose weight.
But they added that mixed-weight populations that were not focused on weigh-loss "showed no effect of water consumption on body weight [or] showed inconsistent results" (such as the effect noticed by McKay), they believed that this was due to the lack of good-quality studies.
Drinking water for weight loss works well with Older Adults
The following studies reported that increasing water consumption helped middle-aged and older adults lose weight.
The weight loss was less in young adults.
In the first study (Dennis, 2012) (4) obese adults aged between 55 and 75 years with a Body Mass Index of 25 to 40, were split into two groups, one drinking half a quart (500 ml) of water before each meal and the other drinking none.
Both groups also followed a low-calorie diet for 12 weeks.
The study found that:
Those drinking water before their main meals lost an additional 4.4 lbs. (2 kg) compared to the "non-water group".
The "water" group also had a 44% greater weight loss than the non-water group.
Another study (Davy, 2008) (5) gave "older" obese subjects (mean age of 61.3 years) a 500 ml (half a quart) premeal drink of water. It found a "13% reduction in meal energy intake" which "was not related to sex, age, body mass index, or habitual daily water consumption."
In other words, they ate less, and this was due to having consumed water before their meal.
Energy Intake3>
Energy Intake (EI) is how many calories are consumed during a meal.
A third study (Walleghen, 2007) (6) compared the energy intake during meals of healthy non-obese subjects which were grouped into young (age: 21 - 35 years) and older (age: 60 - 80 years) cohorts. Each group was further subdivided into sub-groups that were either given water or not.
Walleghen and her team found that:
Young subjects ate the same amount of calories whether they had or hadn't drank water.
Older subjects who had drank water ate fewer calories (8.5% less) than those who hadn't.
Hunger (satiety) and fullness were higher in older subjects.
All those who had drank water (older and younger) had better fullness ratings than those who hadn't drank water.
Their Conclusions: "pre-meal water consumption reduces meal energy intake in older but not younger adults."
Why does drinking water cause Weight Loss?
Which are the mechanisms that cause you to lose weight by increasing water consumption?
Below we will look into three possible ways that drinking more water impacts your metabolism leading to weight loss:
1. Water is a Zero Calorie liquid
Water itself is a zero-calorie drink, so for some people, replacing soft drinks, sweetened beverages such as coffee or tea, or fruit juices with water is a calorie lowering alternative.
Calories in Food
The international unit for energy in food is the kilojoule or kJ. However, the most commonly used unit is what everyone calls calorie (abbreviated Cal).
One Cal is equivalent to 1000 "small" calories, or in other words, one Cal is equal to one kilocalorie (kcal).
Just as an example, a 12 fl oz can (355 ml) of regular Coca-Cola has 140 Cal, all of them from sugar! (1.4 oz. - 39 g of sugar in the can).
A sports drink like a Lemon Lime Gatorade also has 140 Cal (20 fl oz - 591 ml) all of them carbohydrates including 1.3 oz. - 36g of sugar.
Alcoholic beverages are also loaded with calories (a 12 fl oz Budweiser packs 145 Cal).
Switching from a sugar or a high-fructose laden drink to plain water can contribute to a lower energy intake and, potentially, to lower body weight.
Tate (2012) (7) explored this option by studying a group of obese and overweight adult men and women with an average Body Mass Index or BMI of 36.3.
What is BMI?
Body Mass Index or BMI is a relationship between a person's height and weight. Although it does not measure your body fat directly, it provides a good estimate of a person's weight type (obese, overweight, normal, or underweight).
It is widely used because it is an easy and inexpensive way to define a person's body fat.
Tate's subjects substituted caloric beverages with non-caloric ones: either water (Water Group) or diet beverages (DB).
A control group (AC) was not instructed on what beverages to drink. All participants were given information on how to modify their diets to lose weight. The trial lasted six months, and the study found that:
All three groups lost some weight, but very little: on average it was approximately a drop of 2%.
The "Water Group" lost 2.03% of their weight, the "DB" group lost 2.5%, while the "AC" control group lost the least weight: 1.76%.
The fasting glucose (blood sugar) improved in the "water" group. The "DB" group improved too but was similar to the "AC" control group.
Those who were assigned to the beverage replacement groups ("water" and "DB") were 2 times as likely to have achieved a 5% weight loss than were the "AC" participants.
The authors concluded that: "replacement of caloric beverages with noncaloric beverages as a weight-loss strategy... could have public health significance and is a simple, straightforward message."
Should you drink Water or Diet Beverages?
Tate's study showed that water or a diet beverage is less fattening than a sweetened drink. But, which one is better?
A study (Madjd, 2015) (8) addressed this issue. It involved overweight and obese women with a BMI of 27 to 40, aged 18 to 50, who usually drank Diet Beverages (DB). The authors split them into two groups during a 24-week weight loss program:
One group replaced their DB with water ("water" group), while the other continued drinking DB. The results were the following:
The "water" group lost 15.7% more weight than the DB group (average of 19.5 lb - 8.8 kg vs. 16.8 lb - 7.6 kg).
"Water" group's fasting insulin also improved more than that of the DB subjects.
The fasting glucose and waist circumference were similar in both groups.
The authors reported that "Replacement of DBs with water after the main meal may lead to greater weight reduction during a weight-loss program [and] may also offer clinical benefits to improve insulin resistance."
Take-home point: Water is better
Drink water or sugar-free sodas and you will lose more weight than if you drink regular sodas or fruit juice.
Water allows more weight loss than sugar-free beverages and it improves insuline sensitivity.
Another study (An, 2013) (9) reviewed data involving almost 125,000 men and women over four years and found that: everyone gains weight over the years.
All of the participants gained an average of 3.2 lb (1.45 kg) during the study. Which confirms the current global "fattening" trend.
However "increasing plain water and coffee intake was inversely associated with weight gain" meaning that those who drank more water and coffee gained less weight than the other subjects.
An's team concluded that "substitution of sugar-sweetened beverages or fruit juices by non-caloric beverages, like plain water, is related to less weight gain."
The table below summarizes their findings. Adding an extra cup of one of these drinks reduces weight gain by (slows down putting on weight!):
Adding one extra cup per day of:
Reduction in weight gain
Water
-0.29 lb (-0.13 kg)
Coffee
-0.31 lb (-0.14 kg)
Tea
-0.07 lb (-0.03 kg)
Diet Beverages
-0.22 lb (-0.10 kg)
Replacing one serving per day of a sugar-sweetened beverage for a cup of water led to 1.1 lb less weight gain (0.49 kg) during the four years compared to those who kept on drinking sweetened drinks.
If one serving of fruit juice was replaced by water the subjects experimented 0.77 lb (0.35 kg) less weight gain than those who made no changes.
The message is clear: replace sugar-sweetened beverages with unsweetened ones such as water, tea, coffee, or diet beverages, and you may not lose weight, but you will gain less weight than if you stuck to your "bad" habits.
Coffee or Water?
Killer (2014) (10) compared the effects of drinking coffee or water on hydration.
They debunked the idea that drinking coffee should be avoided to maintain a fluid balance: Killer studied 50 young men who drank either 800 ml (4 cups) of coffee or water and found that "There were no significant changes in TBW (Total Body Water) from beginning to end of either trial."
The coffee drinkers lost a bit more sodium through their urine.
The other finding was a small yet progressive daily weight fall in both Coffee and Water groups of almost one pound (0.4 kg).
Another plausible mechanism is that an increased water intake drives "thermogenesis" (you burn more energy to "digest" the water) which in turn leads to weight loss:
Thermogenesis
Thermogenesis or the "Thermogenic Effect" of food is the energy required for digesting and absorbing food, and the stimulating influence that food has on the body. The word combines the Greek words "Thermos" (heat, warmth) and "Genesis" (origin).
Studies on additional energy expenditure
A study by Girona (2014) (11) had twelve subjects drink half a quart (500 ml) of cold and room-temperature water.
The researchers found that the subject's energy expenditure increased by 3% above their usual levels during the 90 minutes that followed drinking the water.
They concluded that the body consumed additional energy to heat the water to body temperature.
Another positive side effect was a reduction in the heart rate and therefore less workload for the heart.
From a physical point of view, heating one ounce (28 g) water from around 50°F (10°C) to body temperature (98.6°F - 37°C) requires an expenditure of only 0.8 Calories. That means that drinking one glass of cold water would only burn extra 5.4 Calories compared to drinking water at body temperature. But with a daily intake of 70 ounces of water it adds up to almost 400 Cal.
Boschmann, (2003) (12) studied the effect of water on thermogenesis and found that:
Drinking 500 ml of water increased the metabolic rate by 30% with a thermogenic response of around 24 Calories. Half of this was due to having to warm water from room temperature to body temperature. But why did the body burn even more energy than was needed to heat the water? They didn't explain this effect.
They concluded that this thermogenic effect "should be considered when estimating energy expenditure ... during weight loss programs."
However, another study (Brown, 2006) (13) failed to replicate this finding, detecting only a small 4.5% increase in energy expenditure under similar conditions.
But another study confirmed that water-induced thermogenesis helped overweight girls lose weight (Vinu, 2013) (14):
Vinu's subjects drank 500 ml of water before each of the three main meals during eight weeks, resulting in a bodyweight and BMI decrease of 2.2%.
Take-home point:
Your body burns extra calories to digest the water, especially if it is cold.
3. Water suppresses appetite
This is based on the idea that once the stomach fills up with water, it signals the brain-stimulating a feeling of fullness and satiety.
This "appetite suppression" theory has been studied with mixed results:
Dennis (4) found that "Water consumption acutely reduces meal energy intake (EI) among middle-aged and older adults..." implying that fewer calories were eaten due to a feeling of satiety after drinking water.
McKay's study (2) didn't find a lower caloric intake in obese subjects (only "normal" weight participants ate less during lunch after having drank water), yet they did detect that "water intake suppressed liking of food items in all participants and hunger in females."
Walleghen's study (6) suggests that hunger is suppressed in older adults due to their slower gastric emptying time which is around 34% (12 minutes) longer than that of younger adults. This may give time for the brain to recognize satiety and signal to stop eating.
Walleghen also found that "healthy older adults report less hunger and more fullness in response to a meal" than younger adults, suggesting that aging may explain the different sensations of hunger or fullness.
Water and Hormones interact
The stomach has stretch receptors in it that detect its change in size as it fills with food (or, in our case, water). These receptors send signals to the brain to indicate satiety.
Additionally, the first phase of digestion begins in the duodenum, the first segment of the small intestine, and the cells located in the walls of the small intestine release "gut hormones" known as Cholecystokinin (CCK) which affect the brain reducing the feeling of hunger.
Kusano (2005) (15) looked into the effects of water on the gastrointestinal tract following a meal. They found that drinking 500 ml of water 1 hour after a standard 560 Kcal meal increased the level of CCK in the blood, reducing the sensation of hunger.
A study by Camps (2018) (16) explored the effect of "gastric distention" or stomach stretching after a meal and how it interacts with the brain. They set up an MRI scan to measure both stomach content and blood flow in the brain after the subjects drank either a low volume (50 ml) or a high volume (350 ml) of water.
They found that those who drank the "high volume" of water had significantly increased fullness and decreased hunger than those who drank the "low volume" of water.
The increased water load activated a brain area called the mid-temporal gyrus which may have some yet unknown role in satiety.
Thornton (2016) (1718) proposed that hydration leads to bodyweight loss mainly through a reduction in feeding and a loss of fat due to increased lipolysis.
Thornton pointed out that "this increased water intake... produced a marked decrease in adiposity... unblock[ing] fat metabolizing mechanisms... the increased water intake per se allows cells to hydrate better and thus regulate fat metabolism better."
Lipolysis: Fat Metabolism
Lipolysis is a process that breaks down fats and turns them into glycerol and free fatty acids to provide energy to the body.
The increase in lipolysis after drinking water may be due to the increase in cell volume as the cells absorb the extra water. This in turn increases mitochondrial activity (the mitochondria produce the cell's energy and regulate cellular metabolism).
Heightened metabolism then increases lipolysis in the fatty tissue.
Another mechanism proposed by Thornton involves the kidneys: higher hydration causes the release of atrial natriuretic peptide (ANP) which activates a protein called uncoupling protein 1 (UCP1), which increases fat metabolism and a loss of body weight. ANP also increases sodium excretion by the kidneys.
Take-home point:
Water makes you feel less hungry and helps burn fat.
Conclusions
There is considerable evidence supporting the notion that drinking unsweetened beverages (water, diet drinks, coffee, or tea) will help you lose weight.
In the meantime, you should check if you are well hydrated. Work out your fluid intake and compare it with the recommended guidelines of the National Academy of Medicine (NAM) for adults:
91 ounces of total water for women (2.7 liters)
125 ounces of total water for men (3.7 liters)
"Total water" means water from all the beverages and foods consumed each day. Estimate that 20% of your water comes from food (vegetables, beef, eggs, meat, fruits).
Can I use coconut oil on my face? Can it treat eczema? Pros and Cons, uses of coconut oil for your skin and hair. Antioxidant, UV protection. See the recipe for a body lotion
Your skin may be sensitive to cosmetics or their ingredients, learn how about sensitivity tests and if your skin is sensitive or sensitized. Treatments, tips on safe use of cosmetics
Aloe Vera, a natural aid for skincare. Pamper your skin and face and cool acne. Learn the benefits and side effects to heal wounds, moisturize, and how to use it...
The material appearing on Fit-and-Well.com is for educational use only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment.
We do not endorse products or services that are advertised on the web site. Advertisers and advertisements that appear on this website are served by a third party advertising company.
Fit and Well: Health, Fitness, Diet & Food information website Our website is a reliable source of up-to-date, scientifically proven information on health, fitness, wellbeing, diet, food, and nutrition.
Our mission: Educate and inspire with reflective evidence-based reasoning. Information and News that you can trust.