For a long time, drinking water has been thought to help with weight loss.
In fact, 30–59% of US adults who try to lose weight increase their water intake.
Many studies show that drinking more water may benefit weight loss and maintenance.
We’ve partnered with WW (Weight Watchers Reimagined) to help you understand how drinking water can help you lose weight.
Drinking Water Can Make You Burn More Calories
Most of the studies listed below looked at the effect of drinking one, 0.5 liter (17 oz) serving of water.
Drinking water increases the amount of calories you burn, which is known as resting energy expenditure.
In adults, resting energy expenditure has been shown to increase by 24–30% within 10 minutes of drinking water. This lasts at least 60 minutes
Supporting this, one study of overweight and obese children found a 25% increase in resting energy expenditure after drinking cold water.
A study of overweight women examined the effects of increasing water intake to over 1 liter (34 oz) per day. They found that over a 12-month period, this resulted in an extra 2 kg (4.4 lbs) of weight loss.
Since these women didn’t make any lifestyle changes except to drink more water, these results are very impressive.
Additionally, both of these studies indicate that drinking 0.5 liters (17 oz) of water results in an extra 23 calories burned. On a yearly basis, that sums up to roughly 17,000 calories — or over 2 kg (4.4 lbs) of fat.
Several other studies have monitored overweight people who drank 1-1.5 liters (34–50 oz) of water daily for a few weeks. They found a significant reduction in weight, body mass index (BMI), waist circumference and body fat.
These results may be even more impressive when the water is cold. When you drink cold water, your body uses extra calories to warm the water up to body temperature.
You can track your water intake through the WW app. Doing so can help you meet your goals while staying hydrated.
Drinking Water Can Make You Burn More Calories
Some people claim that drinking water before a meal reduces appetite.
There actually seems to be some truth behind this, but almost exclusively in middle-aged and older adults (11Trusted Source).
Studies of older adults have shown that drinking water before each meal may increase weight loss by 2 kg (4.4 lbs) over a 12-week period.
In one study, middle-aged overweight and obese participants who drank water before each meal lost 44% more weight, compared to a group that did not drink more water (4Trusted Source).
Another study also showed that drinking water before breakfast reduced the amount of calories consumed during the meal by 13%.
Although this may be very beneficial for middle-aged and older people, studies of younger individuals have not shown the same impressive reduction in calorie intake.
Drinking More Water is Linked to Reduced Calorie Intake and a Lower Risk of Weight Gain
Since water is naturally calorie-free, it is generally linked with reduced calorie intake.
This is mainly because you then drink water instead of other beverages, which are often high in calories and sugar.
Observational studies have shown that people who drink mostly water have up to a 9% (or 200 calories) lower calorie intake, on average.
Drinking water may also help prevent long-term weight gain. In general, the average person gains about 1.45 kg (3.2 lbs) every 4 years.
This amount may be reduced by:
It is especially important to encourage children to drink water, as it can help prevent them from becoming overweight or obese.
A recent, school-based study aimed to reduce obesity rates by encouraging children to drink water. They installed water fountains in 17 schools and provided classroom lessons about water consumption for 2nd and 3rd graders.
After one school year, the risk of obesity had been reduced by a whopping 31% in the schools where water intake was increased.
How Much Water Should You Drink?
Many health authorities recommend drinking eight, 8-oz glasses of water (about 2 liters) per day.
However, this number is completely random. As with so many things, water requirements depend entirely on the individual (20).
For example, people who sweat a lot or exercise regularly may need more water than those who are not very active.
Older people and breast-feeding mothers also need to monitor their water intake more closely.
As a good rule of thumb, you should always drink water when you’re thirsty, and drink enough to quench your thirst.
If you find you have a headache, are in a bad mood, are constantly hungry or have trouble concentrating, then you may suffer from mild dehydration. Drinking more water may help fix this.
Based on the studies, drinking 1-2 liters of water per day should be sufficient to help with weight loss.
Here’s how much water you should drink, in different measurements:
However, this is just a general guideline. Some people may need less, while others may need a lot more.
Also, it is not recommended to drink too much water either, as it may cause water toxicity. This has even caused death in extreme cases, such as during water drinking contests.
Take Home Message
Water can be really helpful for weight loss.
It is 100% calorie-free, helps you burn more calories and may even suppress your appetite if consumed before meals.
The benefits are even greater when you replace sugary beverages with water. It is a very easy way to cut back on sugar and calories.
However, keep in mind that you’re going to have to do a lot more than just drink water if you need to lose a significant amount of weight.
Water is just one, very small piece of the puzzle.
How much water should I drink?
We’ve all heard the old adage of 8 glasses of water a day, but in reality everyone has differing hydration needs. Instead, doctors recommend to pay attention to the signals your body is sending.
Generally, you should try to drink before you’re thirsty. By the time you feel parched, you’re already slightly dehydrated. Another way to keep tabs is to check your urine. It should be a pale yellow color. If it’s dark yellow, it’s time to drink some more water.
Read more: Need reminders to drink water? Try this smart water bottle.
If both of these don’t give you enough clues, one more interesting test is to examine your skin elasticity. To do so, use two fingers to pinch your skin on your lower arm or abdomen. Hold it for a few seconds to form a tent-like shape, then let go. If it snaps quickly back into place, you’re adequately hydrated. If it takes some time to return to its shape, you’re probably dehydrated.
The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.
Adda Bjarnadottir is a registered nutritionist in Iceland with a has a BSc and a master's degree in human nutrition. She started out as a writer for Authority Nutrition in 2015 and transitioned over to Healthline in 2017. She now manages writer communications, topic selection, and medical review of all nutrition content.