Now for the water diet (and yes, it really works)

Scientists believe that drinking water can help you to lose weight.

Scientists say drinking water can help you lose weight.

There is a certain type of woman who sips water. Or at least who likes to be seen to be sipping water. She arrives, blow-dried, at the office or school gate carrying an oversized tote. It houses her chic black+blum water carrier with charcoal filter or an on-trend bkr glass water bottle — a favourite of celebrities including Reese Witherspoon, Gisele Bündchen and Jessica Alba — in this season’s colourway of bellini (soft peach) or Sunday (duck-egg blue). She is dewy-skinned and poised, unfazed by the daily treadmill on which we find ourselves. And invariably she is thin.

For the aqua-obsessive, drinking the stuff so openly and so often — even if it’s from bog-standard Volvic or Evian plastic bottles — is never about thirst. Water represents far more than that for those who swallow the endless claims that it leaves you bright-eyed and flushes out toxins. Consuming it is a statement of lifestyle purity, a smug swipe at those of us who take our fluids in more sugary, caffeine-loaded forms.

And there is always the underlying suggestion that water is in some way responsible for their slenderness. For most of those who carry a 500ml water bottle and fill it four or five times a day, the premise has always been that it offsets hunger. Of all the far-fetched benefits associated with drinking copious amounts of water, it is the one that has refused to die.

Scientists have dismissed as largely unproven most of the advantages we thought we knew water held. The idea that it boosts complexion or detoxes the body is considered flawed. Even the widely accepted recommendation to drink eight glasses a day for hydration and good health has been shown to be the stuff of urban legend. Yet when it comes to its use as a slimming aid, the unthinkable is happening — scientists are turning the tide in favour of the “water diet”.

Last week, researchers from the University of Illinois declared, in a paper published in the Journal of Human Nutrition and Dietetics, that the aqua brigade might be on to something. Drinking water, they found, helps you to eat considerably fewer calories as well as less sugar, salt and cholesterol. The study was of considerable size — 18,311 adults were interviewed about what they ate and drank on two days.

Ruopeng An, an assistant professor of kinesiology, and his team showed that drinking up to three glasses of plain water more than usual each day correlated with a consumption of 69 to 206 fewer calories than usual. In just over two weeks that could equate to a pound of fat lost without changing what you eat or how you exercise.

What’s more, the water-drinkers also ate up to 18g less sugar and 235mg less sodium. This, An suggested, was partly due to people substituting water for their usual sweetened drinks, cutting their energy intake, but also because having water in their belly left them feeling fuller.

The concept of pre-loading with water — or drinking it before a meal — is also captivating scientists. Last year, researchers at the University of Birmingham suggested, in their 12-week study of overweight and obese patients, that ordinary tap water could be a potent weight-loss tool. The 84 people who took part were given a weight-management consultation with advice about diet and exercise before being split into two groups. The first group were advised to imagine that they had a full stomach before having breakfast, lunch and their evening meal; the second were instructed to drink 500ml of water half an hour before eating each of their daily meals.

The results of the study, which was funded by the Royal College of General Practitioners and the industry-backed European Hydration Institute, were impressive. Over 12 weeks the water drinkers lost an average 1.3kg (2.87lbs) more than the group who drank no water. T hose who had stuck with their plan and pre-loaded at every meal lost 4.3kg (9.48lb), the kind of weekly losses expected at slimming groups.

Dr Amanda Daley was one of the researchers at the University of Birmingham’s School of Health and Population Sciences who reported the findings in the journal Obesity. She says the results strongly indicated that water is undervalued as a diet aid. “We gave subjects a bottle that would hold 500ml of fluid and just asked them to fill it with tap water and to drink it in one go half an hour before eating,” Daley says. “It seems to act in a particular way, to have more of a satiating effect, when people drink a whole glass of water as opposed to small sips throughout the day.”

So convinced are they of water’s merits that Daley and her co-authors are planning a larger trial over 12 months. “It is such a simple message and something that most people could adopt quite easily,” she says. “We recommended tap water because it’s accessible and inexpensive. You don’t need to buy water in bottles for it to have this effect.”

Yet many people do. Sales of bottled water are at an all-time high in the UK with a market worth pounds 2 billion. According to the market researcher Nielsen, sales rose by 10 per cent in the year to the end of March 2015. Another study suggests that annual bottled water consumption exceeds 40 litres a person, up from 26.9 litres in 2001. However, some sectors of the population barely drink water at all.

Clinical recommendations produced by the European Food Safety Authority say we need 35ml of fluid per kilogram of our body weight every day. For most people that equates to 8-12 cups a day or 2 litres for women and 2.5 litres for men. It doesn’t have to be water, but experts favour it over other drinks, because it is free from calories and additives.

Although there are risks of over-drinking water, leading to intoxication or hyponatraemia, cases are few and far between and you would need to drink two or three times the daily quota to be at risk. “The health-conscious and gym-goers tend to drink enough,” says the nutrition consultant to the bottled water industry, Dr Emma Derbyshire, “but the old, the young and the overweight are thought to be under-consuming water.” Dehydration is a worrying side-effect, but so is an expanding waistline.

Even registered dietitians, who are notoriously reluctant to back anything but the most stringent evidence when it comes to weight-loss claims, have warmed to the water diet. “Water is a key component of our calorie intake and has more influence on the amount we eat than we realise,” says Anna Daniels, a spokeswoman for the British Dietetics Association. “This latest study underlines the need for people to have a better understanding of the benefits of drinking it.”

Daniels favours frequent sipping over pre-loading water before a meal which, she says, can hamper digestion. “Drinking a large amount of water in one go has the potential to dilute the stomach acids needed in the digestive process,” she explains. “I’d recommend little and often. ”

However, you drink it, though, expect the pay-off to be impressive.

“So many people confuse feelings of mild hunger with mild thirst and look for a snack rather than a glass of water,” says the dietitian Dr Sarah Schenker. “Drink more water and it will fill you up a bit, help to reduce snacking and help you to lose weight. Who’d complain at that?”

The Times