Hydration is key for many factors involved in weight loss, including digestion and muscle function. To stay hydrated, females need around 9 cups of water per day and males need around 13 cups. Drinking adequate water may help people lose weight.

Researchers are still unsure why drinking more water helps a person to lose weight, but many studies show some positive correlation between increased water consumption and weight loss.

This article outlines six reasons that drinking water may help a person lose weight. It also looks at how much water a person should drink each day.

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When the stomach senses that it is full, it sends signals to the brain to stop eating. Water can take up space in the stomach, leading to a feeling of fullness and reducing hunger.

A person may also think they are hungry when they are actually thirsty. Drinking a glass of water before reaching for something to eat can help curb unnecessary snacking.

In an older 2014 study, 50 overweight females drank 500 milliliters (mL) of water 30 minutes before breakfast, lunch, and dinner, in addition to their regular water consumption, for 8 consecutive weeks.

The participants experienced a reduction in body weight, body fat, and body mass index (BMI). They also reported appetite suppression.

A study from the previous year yielded similar results.

Learn more about BMI.

Some research indicates that drinking water can help to burn calories.

In another 2014 study, 12 people who drank 500 mL of cold and room temperature water experienced an increase in energy expenditure.

They burned 2–3% more calories than usual in the 90 minutes after drinking the water.

Water may also temporarily increase the body’s resting energy expenditure or the number of calories burned while resting.

Drinking cold water may further enhance water’s calorie-burning benefits because the body expends energy, or calories, by heating up the water for digestion.

When the body is dehydrated, it cannot correctly remove waste as urine or feces.

Water helps the kidneys to filter toxins and waste while retaining essential nutrients and electrolytes. When the body is dehydrated, the kidneys retain fluid.

Dehydration can also result in hard or lumpy stools and constipation. Water keeps waste moving by softening or loosening hardened stools.

Water also helps the body to recover from digestive problems, such as diarrhea and indigestion.

When waste builds up in the body, people may feel bloated, swollen, and tired. Bloating can add inches to a person’s waist.

Staying hydrated is a good way to avoid retaining waste, which may add a few extra pounds.

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It is easy to accumulate liquid calories by drinking soda, juice, or sweetened coffee or tea.

Many people also ignore how many calories they consume in sports drinks or alcoholic beverages.

Replacing even a few high-calorie drinks each day with water or other no-calorie beverages, such as herbal tea, may have long-term weight loss benefits.

In a study from 2015, female participants drank 250 mL of water after lunch each day while attending a 24-week weight loss program. They lost 13.6% more weight than people in the same program who drank the same volume of diet beverages after lunch.

Another study involved 15,765 adults without obesity at the start of the study. They replaced one sugar-sweetened beverage or beer per day with water. Using mathematical models, the results showed that this small change related to a higher incidence of weight loss and less obesity over 4 years.

Without water, the body cannot properly metabolize stored fat or carbohydrates.

The process of metabolizing fat is called lipolysis. The first step of this process is hydrolysis, which occurs when water molecules interact with triglycerides (fats) to create glycerol and fatty acids.

Drinking enough water is essential for burning off fat from food and drink, as well as stored fat.

A mini-review from 2016 found that increased water intake led to increased lipolysis and a loss of fat in animal studies.

One of the most important components of any weight loss plan is exercise.

Water helps muscles, connective tissues, and joints to move correctly. It also helps the lungs, heart, and other organs to work effectively as they ramp up activity during exercise.

Being hydrated reduces the risk of things that can get in the way of a good workout, such as muscle cramps and fatigue.

Always drink water before, during, and after exercise to avoid dehydration.

Keeping water close at hand is essential, especially if exercising in hot, humid, or very sunny conditions.

Read about how often to work out for health, strength, and weight loss.

There is no standard recommendation for how much water to drink. Some people require more or less water, depending on a variety of factors, including:

  • activity level
  • age
  • body size
  • temperature
  • humidity
  • sun exposure
  • health status

The Academy of Nutrition and Dietetics suggests estimates for the total water required daily. Most people get around 20% of their required fluid intake from food. The table below shows estimates of how many cups of water males and females need per day from food and drinks combined and from drinks alone.

From food and beveragesFrom beverages alone
Fluid per day for females11.5 cups9 cups
Fluid per day for males15.5 cups13 cups

It is important to note that some beverages can be dehydrating, so do not count toward a person’s daily fluid intake. Examples include sugar-sweetened and alcoholic beverages.

Read more about dehydrating drinks.

The following tips can help to increase water intake:

  • Drink at least one 8-ounce glass of water with each meal.
  • Carry water in a reusable water bottle.
  • Drink extra water when exercising or during physical activity.
  • Drink extra water when it is warm, humid, or very sunny.
  • Keeping a glass of water near the bed.
  • Eat more soups and liquid-rich meals, such as curries, stews, and smoothies.
  • Eat fruits and vegetables with high water contents, especially berries, grapes, melons, tomatoes, celery, cucumbers, and lettuce.

Below are answers to some frequently asked questions about water and weight loss.

How much water should you drink to lose weight?

People can try drinking more water than the recommended amount, which may increase satiety, reduce hunger, and help them lose weight. The Academy of Nutrition and Dietetics recommends 9 cups of water daily for females and 13 for males. This is in addition to the water people get from their food.

Can water fasting help you lose weight?

Water fasting involves drinking only water and eating no food. People do not consume calories so they will likely lose weight quickly on a water fast. However, water fasting can have adverse effects on the body, and people must consult a doctor before embarking on a water fast.

Drinking plenty of water and other hydrating beverages may help with weight loss in various ways. It can help people feel fuller and reduce hunger, reduce the calories people consume from fluids, and help the body remove waste efficiently.
Females need around 9 cups of water daily, on top of the amount they consume through food. Males need around 13 cups.