For a long time, drinking water has been thought to help with weight loss.
This article explains how drinking water can help you lose weight.
Most of the studies listed below looked at the effect of drinking one, 0.5 liter (17 oz) serving of water.
Supporting this, one study of overweight and obese children found a 25% increase in resting energy expenditure after drinking cold water (7).
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 (8).
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 (8, 9, 10).
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.
Bottom Line:Drinking 0.5 liters (17 oz) of water may increase the amount of calories burned for at least an hour. Some studies show that this can lead to modest weight loss.
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 (11).
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 (4).
Another study also showed that drinking water before breakfast reduced the amount of calories consumed during the meal by 13% (12).
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.
Bottom Line: Drinking water before meals may reduce appetite in middle-aged and older individuals. This decreases calorie intake, leading to weight loss.
Since water is naturally calorie-free, it is generally linked with reduced calorie intake.
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 (18).
This amount may be reduced by:
- Adding 1 cup of water: Increasing your daily water consumption by 1 cup may reduce this weight gain by 0.13 kg (0.23 lbs).
- Replacing other drinks with water: Substituting a serving of a sugar-sweetened beverage with 1 cup of water may reduce the 4-year weight gain by 0.5 kg (1.1 lbs).
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 (19).
Bottom Line:Drinking more water may lead to decreased calorie intake and reduce the risk of long-term weight gain and obesity, especially in children.
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 (21).
As a good rule of thumb, you should always drink water when you're thirsty, and drink enough to quench your thirst.
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:
- Liters: 1–2.
- Ounces: 34–67.
- Glasses (8-oz): 4–8.
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.
Bottom Line: According to the studies, 1–2 liters of water per day is enough to assist with weight loss, especially when consumed before meals.
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.