If you're cutting calories, drinking two cups of water before every meal can help you lose more weight than dieting alone. That’s the finding of a  study presented at the 240th National Meeting of the American Chemical Society in Boston.

“In spite of popular beliefs that this is a weight loss strategy, it had never actually been studied in a clinical trial,” says lead author Brenda Davy, PhD, associate professor in the Department of Human Nutrition, Foods and Exercise at Virginia Tech
 in Blacksburg.

This study followed 48 adults between the ages of 55 and 75 who were on a low-calorie diet for three months. Half the group was told to drink two eight-ounce glasses of water three times a day before every meal. The other half was given no instructions about what to drink or when. After 12 weeks, those who drank the prescribed amount of water before meals lost about 15.5 pounds. The group who didn’t lost about 11 pounds.

“The idea was that this may help to manage hunger and fullness and help them adhere to the low-calorie diet,” says Davy.

Davy believes water works by filling up the stomach with something that has no calories. But she warns that dieters shouldn't attempt this strategy with juice, soda or other high-calorie beverages.

“One important point is that, as Americans, we consume about 400 to 450 calories from beverages over the course of a day. So for people who do consume a lot of calorie-containing beverages, simply replacing the calorie-containing beverages with water could be a way to reduce our calorie intake,” Davy says.
 

Researchers don’t know if increasing water consumption beyond two glasses would increase weight loss even more. That's something they’d like to study in the future. But the researchers caution against taking this strategy to extremes. While rare, it is possible to drink too much water, leading to a condition called water intoxication, which can make you quite sick.

Lawrence Cheskin, MD, director of the Johns Hopkins Weight Management Center and associate professor in the Department of Health, Behavior & Society at Johns Hopkins School of Public Health in Baltimore says this study adds to the body of evidence on this weight-loss strategy, which is helpful.

“I recommend that people fill up their stomachs with something that is zero calories and not just right before a meal but during the day as well,” Dr. Cheskin says. “Sometimes people just need something in their stomach to feel more satisfied. So this is in line with what I recommend. I’m not sure it needs to be water. In fact, that’s not many people’s favorite beverage. I don’t see any problem with it being diet soda or Crystal Light or something with very few calories because you can be filled up just as much or more with other things, too.”