Water. It’s the most fundamental prerequisite for life. It makes up roughly 60% of our bodies. And it’s one of the first things to be recommended to anyone trying to get fit, healthy and lose weight. But exactly how much water should you be drinking if you want to lose weight? And, while we’re on the subject, how does water help you to lose weight?
Firstly, even though the title of this article refers to a specific volume of water, there is no “special” level of consumption that has particular benefits. How much water a person requires depends on many different factors like age, gender, body mass, activity level and climate. A young man who runs 4 times per week and lives in a Mediterranean country will need to drink much more water than a sedentary pensioner in Scandinavia.
While recommending that everyone should drink a gallon of water a day is clearly an oversimplification, the logic behind it is clear: most people would benefit from increasing their water intake. Drinking more water is one of the first moves 30 – 59% of US adults make when trying to lose weight, and they’re not wrong; there is plenty of evidence that drinking water help weight loss and maintenance.
In this article I’m going to explain how drinking water can support your weight loss programme and how to know if you’re drinking enough. Water is an essential nutrient and has plenty of health benefits, some of which I’ll mention later, but there are two main ways it affects your weight. Water has a strong impact on your metabolism as well as significantly influencing your behaviour.
Not surprisingly, the amount of water you drink has an effect on how your body uses food for energy. There is good evidence that drinking water increases your resting energy expenditure, that is the amount of calories your body burns without changing your activity levels. Several studies have shown that drinking a large glass (500ml) of water increases the resting energy expenditure of adults by between 24% and 30% for at least an hour after consumption. Similar effects have also been observed in studies on obese children and overweight women who increased their water intake. By moderately increasing their water intake they all increased the amount of calories they burned without exercise.
What is even more impressive is that, even without any other lifestyle changes, the effect of drinking a little more water adds up to substantial weight loss over the long term. The above mentioned study tracking the overweight women showed that on average they lost an additional 2kg when they increased water consumption.
Other studies where overweight people drank between 1L and 1.5L per day showed overall weight loss, BMI reduction, lower waist circumference and fat loss. What’s interesting here is that the increases in water consumption that have been shown to be effective for weight loss are all pretty moderate. Between 500ml and 1.5L water per day is enough to have a serious effect on your metabolism.
Another interesting feature of water’s effect on your metabolism is that the increase in resting energy expenditure is greater when the water is colder. Basically, this happens because your body needs to expend more energy in order to heat the water up to your body temperature. One easy way to take advantage of this would be by drinking a medium sized glass of water with plenty of ice during the day. It’s a really easy habit to establish and over the long run it could have a major effect on the effectiveness of your weight loss.
Besides increasing your calorie expenditure, drinking more water can help you lose weight by changing your behaviour. You can think of the first way that water does this as the “replacement effect”. Think about it: every time you drink water you’re not drinking something that contains calories like fruit juice, soda, milk, coffee, beer or anything else. Even if you don’t explicitly replace these drinks that contain calories with water, trying to drink more water will cut down on the calories you do drink. You can only drink so much in a given time period, and if you always reach for water first you’ll have less room for everything else.
Replacement of sweetened drinks with water has been shown to decrease weight gain and total energy intake. Moreover, the provision of water fountains and education about the benefits of water in schools decrease the risk of children becoming overweight by 31%.
Besides replacing calories consumed through other beverages, water also has an effect on your feelings of hunger and satiety. When we feel hunger, the feeling arises from a complex combination of factors including blood sugar levels, hormones and how full our bellies are. Water fills some space in your digestive system, sending a signal to your brain that you don’t need to eat just yet and turning down feelings of hunger. And this isn’t just speculation, several studies have shown that drinking water before meals decreases appetite, reduces the amount of calories consumed and increases weight loss.
However, this effect has only been shown in older adults and could potentially be counterproductive to overall health if it leads to not eating enough good quality, nutrient dense food. But the fact remains that it could be very useful for someone trying to implement a well planned calorie-restricted diet. In a case like this drinking water between meals can prevent feelings of hunger and improve adherence to the diet.
Other Health Benefits of Water
So by now it should be clear that water has a big role to play in any weight loss programme but what if you’re already at your ideal weight? There are many reasons to drink plenty of water beyond how it can help shedding a few pounds.
In case you haven’t noticed yourself, water has a huge effect on physical and mental performance. You can become dehydrated when you lose as little as 2% of your body’s water content, and athletes can lose between 6% and 10% of their water content during intense training or competition. Dehydration saps motivation, increases fatigue and harms your body’s temperature control – all things you need to avoid if you want to get the most from your exercise.
As well as harming physical performance dehydration can impact your mental performance by reducing several aspects of brain function. The type of fluid loss that’s common after a moderate intensity session in the gym can harm concentration, impair mood and increase the frequency of headaches. Even more worrying, the same common level of dehydration can bring on feelings of anxiety as well as making your working memory less effective. Drinking plenty of water when you are thirsty, and even adding a pinch of sea salt to your water after exercise, can help prevent these detrimental aspects of dehydration.
Another big benefit to be had from drinking plenty of water is how it improves digestion. Dehydration is a risk factor for constipation so it makes sense that drinking plenty of water is part of the recommended treatment. Carbonated water is particularly effective at relieving constipation, although the reason why is still unclear. Also related to digestion is the beneficial effect of water on kidney stones. Increasing water consumption raises the volume of water passing through the kidneys, diluting the mineral content and slowing or stopping the formation of stones.
Even if you are not actively trying to lose weight there are lots of good reasons to make sure you drink plenty of water and stay hydrated. The improved mental and physical performance from being well hydrated is so enjoyable that I make sure to start my day with a large glass of water, fresh lemon juice and a pinch of salt.
How to Know How Much is Enough
These days it’s very popular to recommend drinking vast volumes of water in order to reap seemingly magical benefits of hydration. The reality is much more mundane. If you eat a healthy diet (like this one) you will get plenty of water from your food. Staple foods like potato, fish, meat and eggs are all around 75% water and most vegetables have an even higher water content. If you eat plenty of these, along with the occasional soup or stew, you might not need as much water as you think. Thankfully, nature has equipped you with a good guide to know how much water to drink: Thirst. If you are not trying to lose weight then sipping water (tea and coffee without milk or sweeteners are just as good) when you feel thirsty is going to keep you hydrated. After exercise more water helps, particularly with added electrolytes (like salt!).
If you are trying to lose weight then drinking a little more water than you normally would can be helpful. Certainly replacing all other beverages that contain calories with water is a great idea but you certainly don’t need to drink a gallon of water a day to get the benefits.