Drinking water before meals can help dieters shed extra pounds, according to a new study published today.
Slimmers can lose an average of 2.3kg (5lb) extra if they drink two cups of water before meals, three times a day.
While it has long been believed that drinking water can help people feel full, there has been very little scientific evidence to support the claim.
So a team of experts in the US decided to test the theory on 48 adults split into two groups
The first group followed a low calorie diet but did not drink any extra water before meals.
Meanwhile, the second group followed the low calorie diet but also drank two cups of water before each meal.
Over the course of 12 weeks, those drinking water lost about 7kg (15.5lb) compared with the non-drinkers, who lost about 5kg (11lb).
All adults were aged 55 to 75.
The experts presented their findings at the National Meeting of the American Chemical Society (ACS) in Boston.
Dr Brenda Davy, senior author on the study, said it was the first randomised controlled trial looking at water consumption and dieting.
Earlier studies have shown that drinking two cups of water before each meal leads to people eating between 75 and 90 fewer calories during that meal.
She added: "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 five pounds more than dieters who did not increase their water intake."
Dr Davy, from Virginia Tech in Blacksburg, Virginia, said water may be so effective simply because it fills the stomach up with a liquid that has no calories.
Diet drinks containing artificial sweeteners may have a similar effect, she said, but people should avoid drinks high in sugar.
"People should drink more water and less sugary, high-calorie drinks," she said. "It's a simple way to facilitate weight management."
The study was funded by the charity the Institute for Public Health and Water Research.