For a long time, drinking water has been thought to help with weight loss.
In fact, 30–59 percent of U.S. adults who try to lose weight increase their water intake (1, 2).
Many studies show that drinking more water may benefit weight loss and maintenance (3).
This article explains 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 (4).
In adults, resting energy expenditure has been shown to increase by 24–30 percent within 10 minutes of drinking water. This lasts at least 60 minutes (5, 6).
Supporting this, one study of overweight and obese children found a 25 percent increase in resting energy expenditure after drinking cold water (7).
A study of overweight women examined the effects of increasing water intake to more than 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 more than 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.
Drinking Water Before Meals Can Reduce Appetite
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).
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 (4, 11).
In one study, middle-aged overweight and obese participants who drank water before each meal lost 44 percent 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 percent (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.
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