How Much Water Should You Drink Per Day?

Your body is about 60% water, give or take.

You are constantly losing water from your body, primarily via urine and sweat. To prevent dehydration, you need to drink adequate amounts of water.

There are many different opinions on how much water you should be drinking every day.

Health authorities commonly recommend eight 8-ounce glasses, which equals about 2 liters, or half a gallon. This is called the 8×8 rule and is very easy to remember.

However, some health gurus believe that you need to sip on water constantly throughout the day, even when you’re not thirsty.

As with most things, this depends on the individual. Many factors (both internal and external) ultimately affect your need for water.

Does Water Intake Affect Energy Levels and Brain Function?

Many people claim that if you don’t stay hydrated throughout the day, your energy levels and brain function start to suffer.

And there are plenty of studies to support this.

One study in women showed that a fluid loss of 1.36% after exercise impaired mood and concentration and increased the frequency of headaches.

Other studies show that mild dehydration (1–3% of body weight) caused by exercise or heat can harm many other aspects of brain function.

Keep in mind that just 1% of body weight is a fairly significant amount. This happens primarily when you’re sweating a lot.

Mild dehydration can also negatively affect physical performance, leading to reduced endurance.

TL;DR: Mild dehydration caused by exercise or heat can have negative effects on both your physical and mental performance.

Does Drinking a Lot of Water Help You Lose Weight?

There are many claims that increased water intake may reduce body weight by increasing your metabolism and reducing your appetite.

According to two studies, drinking 17 ounces (500 ml) of water can temporarily boost metabolism by 24–30%.

The researchers estimated that drinking 68 ounces (2 liters) in one day increased energy expenditure by about 96 calories per day.

Additionally, it may be beneficial to drink cold water because your body will need to expend more calories to heat the water to body temperature.

Drinking water about a half hour before meals can also reduce the number of calories you end up consuming, especially in older individuals.

One study showed that dieters who drank 17 ounces (500 ml) of water before each meal lost 44% more weight over 12 weeks, compared to those who didn’t.

Overall, it seems that drinking adequate amounts of water, particularly before meals, may have a significant weight loss benefit, especially when combined with a healthy diet.

What’s more, adequate water intake has a number of other health benefits.

TL;DR: Drinking water can cause mild, temporary increases in metabolism, and drinking it about a half hour before each meal can make you automatically eat fewer calories. Both of these effects contribute to weight loss.

Does More Water Help Prevent Health Problems?

Several health problems supposedly respond well to increased water intake:

  • Constipation: Increasing water intake can help with constipation, a very common problem.
  • Cancer: Some studies show that those who drink more water have a lower risk of bladder and colorectal cancer, although other studies find no effect.
  • Kidney stones: Increased water intake may decrease the risk of kidney stones.
  • Acne and skin hydration: There are a lot of anecdotal reports about how water can help hydrate the skin and reduce acne. So far, no studies have confirmed or refuted this.

TL;DR: Drinking more water may help with some health problems, such as constipation and kidney stones, but more studies are needed.

Do Other Fluids Count Toward Your Total?

Plain water is not the only drink that contributes to your fluid balance. Other drinks and foods can have a significant effect.

One myth is that caffeinated drinks, such as coffee or tea, don’t help you hydrate because caffeine is a diuretic.

In fact, studies show that the diuretic effect of these beverages is very weak.

Most foods are also loaded with water. Meat, fish, eggs and especially fruits and vegetables all contain significant amounts of water.

Together, coffee or tea and water-rich foods can help maintain your fluid balance.

Trust Your Thirst — It’s There for a Reason

Maintaining water balance is essential for your survival.

For this reason, your body has a sophisticated system for regulating when and how much you drink.

When your total water content goes below a certain level, thirst kicks in.

This is controlled by mechanisms similar to breathing — you don’t need to consciously think about it.

For the majority of people, there probably isn’t any need to worry about water intake. The thirst instinct is very reliable.

There really is no science behind the 8×8 rule. It is completely arbitrary.

That said, certain circumstances may call for increased water intake.

The most important one may be during times of increased sweating. This includes exercise and hot weather, especially in a dry climate.

If you’re sweating a lot, make sure to replenish the lost fluid with water. Athletes doing very long, intense exercises may also need to replenish electrolytes along with water.

Your water need also increases during breastfeeding, as well as several disease states like vomiting and diarrhea.

Furthermore, older people may need to consciously watch their water intake because the thirst mechanisms can start to malfunction in old age.

How Much Water Is Best?

At the end of the day, no one can tell you exactly how much water you need. This depends on the individual.

Try experimenting to see what works best for you. Some people may function better with more water than usual, while for others it only results in more frequent trips to the bathroom.

If you want to keep things simple, these guidelines should apply to the majority of people:

TL;DR:

  • When you’re thirsty, drink.
  • When you’re not thirsty anymore, stop.
  • During high heat and exercise, make sure to drink enough to compensate for the lost fluids.

814 Comments
  • steve plum
    Posted at 14:16h, 23 June

    good info

  • Aptil M Benes
    Posted at 23:38h, 22 June

    Made me thirsty

  • Rosemary Williams
    Posted at 15:31h, 22 June

    Thanks good to know!!!

  • Kent Feig
    Posted at 00:02h, 22 June

    Thank you

  • Wendy Lastivka
    Posted at 21:58h, 21 June

    Great information!

  • Paula Shoaf
    Posted at 19:50h, 21 June

    Good info

  • Good read
    Posted at 22:48h, 20 June

    Water is good

  • Christina Thomas
    Posted at 21:03h, 20 June

    Thank you for the info

  • Latila Powell
    Posted at 03:52h, 20 June

    We all need lots of water.

  • Latila Powell
    Posted at 03:49h, 20 June

    Water!

  • Laquane Turner
    Posted at 00:14h, 20 June

    Good to know. Water is essential.

  • Beverly Zywiczynski
    Posted at 17:08h, 19 June

    Thanks for the info!

  • Gregorio Gonzalez
    Posted at 22:54h, 18 June

    It gets really hot in the cargo warehouse I work at. Using the8x8 rule(eight 8 ounce glasses) will help staying focused and in good health. Thanks for the information.

  • Clarisa J Santos
    Posted at 22:29h, 18 June

    I love water! Tastes so good! My husband always tells me that he’s never met anyone who drinks as much H2O as I do haha

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