For a long time, drinking water has been thought to help with weight loss.

In fact, in a 2019 study that took place between 2015 and 2016, 26.3%Trusted Source of participants reported “drinking a lot of water” in an attempt to lose weight.

Some research suggests that drinking more water is linked with weight loss, but the evidence is insufficient to suggest a direct cause-and-effect relationship.

Read on to learn more about whether drinking water can help you lose weight.

Water consumption is associated with increased sympathetic activity. Your body’s sympathetic system activates things like heart rate and metabolism.

Therefore, drinking water may help increaseTrusted Source your metabolic rate and how much energy (or calories) you burn.

In a 2023 study, researchers found that people who drank 200–250 milliliters (mL) or 6.8–8.5 ounces (oz) of warm water after each meal lost more weight and registered a lower BMI than the control group who didn’t.

In an older study, participants were given water, saline solution, or sucrose to drink. They were then measured for these drinks’ impact on their resting energy expenditure or how many calories they burned at rest.

Room temperature water had no effect, while cooled water showed a small increase of 23 calories burned daily. That said, the sucrose drink showed a much more significant increase in energy expenditure.

This raises doubts about the effectiveness of water by itself for managing obesity. More research should focus specifically on the effect of hot versus cold fluids on energy expenditure.

When you drink water instead of other beverages, which may be high in calories and sugar, you are naturally reducing calorie consumption.

In addition, some people claim that drinking water before a meal reduces appetite. But is this true?

One 2018 studyTrusted Source suggests that drinking water before meals may help make you feel less hungry and eat less, but only in people of average weight and body mass index (BMI). It’s unclear how well this applies to people who are overweight or have obesity.

Research from 2016Trusted Source suggests the following:

• When you are not dieting or monitoring your nutrition, choosing to drink water over high calorie drinks may help you consume fewer calories.
• For people who have problems with their metabolism or have obesity, drinking water may help burn more calories.
• Drinking water can stimulate your body to break down fat without raising your blood sugar or insulin, which may also support weight loss.

That said, another 2018 studyTrusted Source showed no evidence that drinking more water has any effect on body weight among adolescents who are overweight or have obesity. Here too, it can only be concluded that more research is necessary on this subject.

Drinking water may also help prevent long-term weight gain. According to a 2013 studyTrusted Source, the average person gains about 1.45 kg (3.2 lb) every 4 years.

According to the study, subjects who consumed 1 extra cup of water daily lowered their weight gain by 0.13 kg (0.23 lb). Those who substituted a serving of a sugar-sweetened beverage with 1 cup of water reduced their 4-year weight gain by 0.5 kg (1.1 lb).

Sugar-sweetened beverages can include a drink such as a can of Pepsi, which contains 25 calories and almost 7 g of sugar.Trusted Source

In a newer 2019 reviewTrusted Source, researchers found that the results of all the studies indicated that drinking more water was linked with more weight loss.

The weight loss ranged between 0.4–8.8 kg, and the mean weight loss was 5%. However, the researchers said the most weight loss was seen when water was the beverage of choice rather than high caloric options. This, once again, suggests that water consumption itself did not cause weight loss.

Many health authorities recommend drinking eight 8-oz glasses of water (about 2 L) per day.

However, a 2017 studyTrusted Source actually found no concrete association between drinking this specific amount of water daily and weight loss in adolescents who were overweight or had obesity.

In addition, water requirements actually dependTrusted Source entirely on the individual. For example, people who sweat a lot or exercise regularly may need more water than those who are not as active. Older people and nursing parentsTrusted Source also need to monitor their water intake more closely.

Keep in mind that you also get water from many foods and beverages, such as coffee, tea, meat, fish, milk, and especially fruits and vegetables.

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 dry skin, dark urine, or feel unusually tired, you may be mildly dehydrated. Drinking more water may helpTrusted Source fix this.

Here’s how much fluids you should typically drink in a day in different measurements:

• Liters: 2.2 L for females and 3 L for males
• Ounces: 74 oz for females and 101 oz for males
• Glasses (8 oz): 9 cups for females and 13 cups for males

However, this is just a general guideline. Some people may need less, while others may need a lot more. For specific information about your water intake, you can talk with a healthcare professional.