Researchers reporting the results of a clinical trial at a conference in the US said they found participants who drank two cups of water before each meal lost an average of 5 pounds more weight over a 12-week calorie controlled diet than those who followed the same diet but did not drink the water.

Dr Brenda Davy, associate professor in the Department of Human Nutrition, Foods and Exercise in the College of Agriculture and Life Sciences at Virginia Tech in Blacksburg, Virginia, and senior author of the study, told the 240th National Meeting of the American Chemical Society (ACS) that is taking place in Boston 22 to 26 August, that theirs was the first randomized controlled trial to show that increasing water intake is an effective way to lose weight.

The study, which is yet to be published in a peer-reviewed journal, is a follow-on from an earlier one where Davy and her team found middle aged and older people consumed between 75 and 90 fewer calories per meal if they drank two cups of water just before they started eating.

In the latest study, Davy said they found:

“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.”

She urged people to cut down on sugary, high calorie drinks and drink more water:

“It’s a simple way to facilitate weight management,” said Davy.

Davy said while there are lots of anecdotal reports, some going back a long time, that water can help people lose weight, there is surprisingly little scientific evidence. Some studies have alluded to it, but this is the first “gold standard” clinically controlled trial to have looked at the claim by comparing those that did and those that did not drink water before meals.

For the study, Davy and colleagues enrolled 48 adults aged from 55 to 75 years and randomly assigned each to one of two groups: the water drinkers and the non-water drinkers.

The water drinkers drank two 8-ounce cups of water just before they started to eat each meal, while the non-water drinkers did not. An 8-ounce cup is half a pint, or just under a quarter of a litre (237 ml).

Both groups ate a low-calorie diet during the 12 weeks of the study. Over this period, the water drinkers lost an average of 15.5 pounds (7 kg) while the non-water drinkers lost 11 pounds (5 kg).

Davy said the reason drinking water before the meal works is simply because it has zero calories but you have the sensation of feeling partly full before you even start eating, resulting in fewer calories consumed during the meal.

She also said replacing sweetened calorie rich drinks during the day with water is also a good way to reduce calorie intake. For example a 12-ounce can of regular soda (about 350 ml) has about 10 teaspoons of sugar, or 150 calories.

Official bodies like the National Academies’ Institute of Medicine, an agency that advises the Federal Government, say healthy people should let natural thirst guide them on how much water to drink, but they generally recommend this should result in about 9 cups of fluids a day, including water, for women and 13 cups for men.

However, drinking too much water can be dangerous and results in a rare but serious condition called water intoxication, warned Davy.

Source: American Chemical Society.

Written by: Catharine Paddock, PhD