It must rate as one of the simplest diets, but scientists have nevertheless shown that drinking water before meals causes significant weight loss.
Over the course of three months people who sipped two glasses of water before eating lost about 15 pounds compared to the 11 pounds lost by a comparable group of people following the same low-calorie diet.
The study suggests that water could help to reduce calorie intake either by swelling the stomach and making a person feel more full, or by making it less likely that someone will sip sugary drinks with their meal.
Brenda Davy, an associate professor at Virginia Tech in Blacksburgh, told the annual meeting of the American Chemical Society that the research was the first scientifically controlled study of whether water could play a role in dieting.
"We found in earlier studies that middle-aged and older people who drank two cups of water before eating a meal ate between 75 and 90 fewer calories during that meal. In this recent study, we found that over the course of 12 weeks, dieters who drank water before meals, three times per day, lost about 5 pounds more than dieters who did not increase their water intake," Dr Davy said.