It is often said that one of the things you should do every day, if you are trying to lose weight, is drink plenty of water.
Some advice online also says you should drink about a gallon (about 4.5 liters). The claim says that water helps burn calories and reduce appetite, which in turn leads to weight loss.
But while we all wish losing weight was that easy, there is unfortunately little evidence to support these claims.
Myth 1: Water helps burn calories
One small study of 14 young men found that drinking 500ml of water increased resting energy expenditure (the amount of calories the body burns before exercise) by about 24%.
And while that may sound great, this effect only lasted an hour. And it wouldn't translate into much of a difference at all. An adult weighing an average of 70 kg uses only 20 extra calories, or a quarter of a biscuit, for every 500 ml of water they drink.
Another study of just eight young adults saw an increase in energy expenditure when the water was cold in the refrigerator, with a very modest 4% increase in calories burned.
This may be because the body needs to use more energy in order to bring the water temperature up to body temperature, or because it takes more energy to filter the increased volume of fluid through the kidneys. Again, this effect only appeared for about an hour.
So, while this may be scientifically possible, the actual increase in calories burned is minimal.
It is also worth noting that all of this research was on healthy young adults. More research is needed to see if this effect also appears in other groups (such as middle-aged and older adults).
Myth 2: Water with meals reduces appetite
Again, this claim seems reasonable, because if your stomach were at least partially filled with water, there would be less room for food - and so you would end up eating less.
There are a number of studies that support this fact, especially those conducted on middle-aged and older adults.
But one study showed that middle-aged and older adults lost 2 kg over a 12-week period when they drank water before meals, compared to people who didn't drink any water with their meal.
On the other hand, the younger participants (between the ages of 21 and 35) did not lose any weight, regardless of whether or not they drank water before their meal.
But since the study did not use blinding (where information that might affect the participants is withheld until after the experiment is over), it means that the participants may have learned why they were drinking water before their meal. This may have prompted some participants to intentionally change how much they ate in the hope that this would lead to greater changes in weight loss.
However, this does not explain why this effect was not observed in younger people, so it will be important for future studies to investigate why this is the case.
Although there may be some appetite-reducing effects of water, it appears that it may not lead to a change in weight in the long term.
Water just isn't enough
There is a good reason why water alone is not effective in regulating appetite. If that had happened, prehistoric humans would have starved to death.
But although appetite and satiety do not exactly correspond to the ability to lose weight, it can be a useful starting point. Part of what helps us feel full is our stomach. When food enters the stomach, it stimulates stretch receptors which in turn trigger the release of hormones that tell us that we are full.
But since water is a liquid, and it empties quickly from our stomachs - that means it doesn't actually fill us up. Even more interesting is that due to the shape of the stomach, liquids can bypass any semi-solid food content that is being digested in the lower part of the stomach.
This means that water can still be emptied quickly from the stomach. Therefore, even if taken at the end of a meal, it may not necessarily increase your feeling of fullness.
And if you're trying to eat less to lose weight, drinking extra water may not be a great solution. But there is evidence to show that when water is mixed with other substances (such as fiber, soups, or vegetable sauces) it can delay how quickly the stomach empties, meaning you feel fuller for longer.
Replacing high-calorie drinks such as soda and alcohol with water may be an easy way to reduce the calories you consume each day, which may help with weight loss.
The report was prepared by Duane Mellor, Lead for Evidence-Based Medicine and Nutrition from Aston Medical School at Aston University.
Australian Scientists : Healthy foods can put you at risk of "fatal" diseases
Experts warn that so-called healthy foods can put you at risk of several diseases, the silent killers.
Brown bread, low-fat yogurt and protein bars were chosen for the study conducted by Australian scientists.
Despite being considered the healthy choice, these foods can actually increase the risk of a number of fatal diseases such as heart attacks and high blood pressure.
The researchers found that women who ate more highly processed superfoods such as these "healthy" choices increased their risk factor by 39%.
The team followed the diets of 10,006 women, ages 46 to 55, for 15 years.
"Ultra-processed foods tend to be lower in fibre, higher in salt and sugars, and all of these are known to be anti-heart disease prevention factors," Anushria Pant, from the University of Sydney, told the European Society of Cardiology conference in Amsterdam.
A lot of foods are advertised as "healthy" because they are low in calories, and when we look at the salt content, it's very high. We know that high salt means high blood pressure.
And she warned that British women may be at particular risk because their diet usually contains 57% of these foods. This is more than a third more than the highest amount in the study.
Previous research has linked ultra-processed foods to obesity, type 2 diabetes and cancer.
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health