Drinking water with a meal DOES fill you up: Scans reveal exactly how both the stomach expands and brain reacts to make you feel full
- Scientists used MRI scans to study stomachs and brains when eating
- They asked participants to drink large or small glass of water
- Stomach expanded and sent signals to the brain suggesting it was full
- Follows study which found dieters lost more when drinking with meals
Drinking a large glass of water with a meal can help you feel fuller, a new study has found
Dieters have long been told one key to shedding unwanted pounds is drinking more water before or during meals.
Now scientists believe they have discovered exactly why it can make people feel full.
Scans taken of both the stomach and brain while eating show how one responds to the other during treatment.
Researchers from Wageningen University in the Netherlands compared the images taken a different times during meals, to how full people felt.
They found a simple change such as drinking more water can alter messages sent from the stomach which are interpreted as fullness by the brain.
It means anyone looking to lose weight or cut down on eating would benefit from a large drink with their meals.
The study follows another published in the journal Obesity which found dieters lost an extra 4lb over 12 weeks when they drank 500ml of water with a meal.
In the experiment, people were asked to drink a milkshake on an empty stomach, which was followed by a small, 50ml glass, or large 350ml glass of water
MRI scans were used to see how the different amounts of water affected stretching of the stomach.
The large glass of water doubled the stomach content compared to the small glass - and those who drank the large glass also felt less hunger and felt fuller.
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Scientists said the new approach - combining information obtained simultaneously from MRI images of the stomach, feelings reported by participants, and brain scans - offer new insights into how feelings of fullness work.
For example, they found that activation part of the brain area called the mid-temporal gyrus, part of the brain associated with emotion, which seemed to be influenced by the increased water load in this experiment.
'Combining these types of measurements is difficult, because MRI scanners are usually set-up to perform only one type of scan,' said Guido Camps, lead author of the study.
'We've been able to very quickly switch the scanner from one functionality to another to do this type of research'
The MRI scan shows a person's stomach after drinking a milkshake with a small glass of water (in red)
When participants drank a much larger glass, it caused their stomach to swell more and feel fuller
The more the stomach was extended, from 4mm (left) to 10mm (right) from drinking water, the more brain activity there was in the insula region of the brain (yellow)
'In conclusion, we've found that simply adding water increases stomach distension, curbs appetite in the short term and increases regional brain activity.'
The scientists developed the combined MRI method as part of the European Nudge-it research project, which seeks to discover simple changes that promote healthier eating.
They will use it to search for a brain signature that leads people to decide to stop eating, to determine how strategies like water with a meal can be effective at feeling fuller sooner.
The study will be reported this week at the annual meeting of the Society for the Study of Ingestive Behaviour in Portugal.
WHY WE SHOULD EAT WATER, NOT DRINK IT
Health enthusiasts are arguing we should actually be eating more water-rich foods and drinking less.
Drinking water can cause it to pass straight through our system, flushing out vitamins and minerals as it does - while eating it allows it to get into our cells,
‘Healthy hydration is about the water you hold in the body, not the water you drink that passes straight through,’ says Dr Howard Murad, associate clinic professor of medicine at the University of California, Los Angeles, and author of The Water Secret.
The water in food is surrounded by other molecules that help it get into our cells more easily, and ensure it stays in our system for long enough to be put to good use.
Health enthusiasts are arguing we should actually be eating more water-rich foods - such as cucumbers, lettuce, courgettes and radishes - and drinking less
‘When we eat water-rich foods, we absorb water more slowly because it is trapped in the structure of these foods,’ says Dr Murad.
‘That slow absorption means the water in food stays in our bodies longer, and brings a multitude of additional benefits.’
In an average day, a quarter of our liquid comes from our food. Almost all food has some water in it (even a slice of bread can be as much as 33 per cent).
Fruit and vegetables are the most water-laden, with cucumbers, lettuce, courgettes and radishes boasting more than 95 per cent.
In fact, studies show that fruit and vegetables can hydrate the body twice as effectively as a glass of water.
One study, by researchers at the University of Aberdeen Medical School, found that the natural sugars, proteins, mineral salts and vitamins in water-rich fruits and vegetables means they also supplement the nutrients lost through exercise.
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