Researchers say water fills up the stomach without adding calories.
"People should drink more water and less sugary, high-calorie drinks. It's a simple way to facilitate weight management," study author Dr. Brenda Davy told the BBC News.
University of Rochester Medical Center obesity specialist Dr. Stephen Cook says, "It is one of the safest things we can recommend to help people lose weight."
The findings were reported Monday at the American Chemical Society's annual meeting in Boston.