Does Drinking Water Help You Lose Weight?

Written by Rachel Reiff Ellis
Medically Reviewed by Christine Mikstas, RD, LD on June 05, 2025
5 min read

You've probably heard many of the ways water is good for you – it helps move waste out of your body, helps your cells work the way they should, lubricates and cushions joints, and much more. Water keeps you alive and kicking.

But drinking water may also help you reach your weight loss goals. The reasons are many, but what it boils down to is this: The better hydrated you are, the better your body's systems function. And that includes the systems involved in weight maintenance. 

Your metabolism is all the chemical reactions that happen in your body to keep you alive. "High" metabolism means your body burns calories quickly, and "low" metabolism means it burns them more slowly. Doctors call this your metabolic rate. 

How much water you drink has a direct impact on your metabolism. Water is a critical part of your body's enzyme activities and biochemical reactions, including:

  • Glycolysis, or the breaking down of glucose for energy
  • Beta-oxidation, which is the burning of fat
  • Protein synthesis, the process where cells make protein 

Certain organs that play a part in metabolism need water to work well, including your liver and kidneys. 

"If you're dehydrated, the body may shift more metabolic burden to the liver, reducing its ability to burn fat," says Caroline Susie, RDN, LD, a spokesperson for the Academy of Nutrition and Dietetics.

Does drinking water burn calories?

Calories are a measure of energy. You take in calories through food, and that powers your body. The number of calories you take in has an effect on your weight. If the calories you use each day as you move and function are about the same as the calories you take in, your weight should stay about the same. This is because your body stores extra calories as fat. 

Water itself has zero calories and doesn't give you energy, but it does play a role in how your body uses calories.

Is it possible that the simple act of gulping down your H2O could burn calories? To a small extent, yes, says Susie. It's a process called water-induced thermogenesis.

And you may get an even greater effect if the water you drink is cold. Your body uses energy to make the fluids you drink warm up to body temperature, and the more energy that takes, the faster your metabolism.

"[A study] found that drinking 500 mL – or about 17 ounces – of water increased metabolic rate by approximately 30% in healthy men and women," Susie says.

Researchers clocked the start of the effect about 10 minutes after the people in the study drank their water, and things peaked around 20 to 30 minutes later. The result? About 24 kilocalories burned. 

Does drinking water burn fat?

Drinking water itself isn't going to burn belly fat. But staying hydrated plays an indirect part in fat loss because it supports certain systems in the body.

"Adequate hydration is essential for lipolysis, the breakdown of fat," says Susie. "The first step in fat metabolism is hydrolysis, which literally requires water. Staying well-hydrated also ensures efficient functioning of the liver and kidneys, which are involved in metabolizing stored fat."

When it comes to weight management and water, timing may also matter. Drinking water before meals will tend to both reduce your hunger and have modest weight loss benefits, says Marschall Runge, MD, PhD, executive vice president for medical affairs and CEO of Michigan Medicine and dean of the University of Michigan Medical School. 

"If you drink [about 17 ounces] half an hour before meals, there are studies that show modest weight loss and much better weight control," he says. "Your stomach expands, and that changes the hormones that we all have that signal our need to eat." 

In other words, filling your belly with water makes you feel fuller before you eat, and you tend to eat less as a result.

There's no one-size-fits-all answer to the "correct" amount of water you need to drink a day for optimal health. Your water needs vary by your size, age, medical conditions, activity level, and other things.

"The general recommendation is to drink 2 to 3 liters a day – that's about 10 cups of water a day, 10 eight-ounce cups," says Runge. "People who do that tend to have less trouble with overeating and tend to feel better."

Talk to your doctor about how much water you should be getting daily to meet your health and weight loss needs.

Water can also influence weight loss indirectly. Drinking enough water helps with:

  • Appetite control. It's common to mistake thirst for hunger and eat when what your body really needs is water.
  • Energy levels. Even mild dehydration can cause fatigue, leading to lower physical activity. This affects your overall energy level use.
  • Sleep quality. When you're hydrated, you sleep better. Dehydration messes with your sleep-wake cycle and reduces the amount of time you're asleep. Studies show that sleep deprivation disrupts your metabolism, increases your hunger hormones, and makes you less likely to exercise.
  • Better digestion. Water helps break down your food, soften your stool, and prevent constipation so the foods you eat digest well.

If you're taking GLP-1 receptor agonists like semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound) – especially for weight loss – staying well-hydrated becomes even more important, says Susie. 

"These medications can increase your risk of dehydration due to both side effects and reduced appetite, which can cause people to unintentionally drink too little water," she says. 

Another positive about staying well-hydrated while taking GLP-1 receptor agonists is that it makes you less likely to get constipated, which is another common complaint from people who take the drugs, says Runge.

"Part of what those meds do is they slow the progression of food through your stomach and through your digestive tract," he says. 

Some of the other common side effects of GLP-1 receptor agonist drugs that can lead to dehydration include:

  • Nausea
  • Vomiting
  • Diarrhea
  • Decreased appetite or thirst

If you're not intentional about your water intake, even mild symptoms can dehydrate you, so it's important to make it a priority, says Susie.

Drinking enough water helps your body work better, and that includes improving the processes that burn calories and fat. Drinking water, especially cold water, can slightly boost your metabolism and help you burn a few extra calories. Drinking water before meals can make you feel fuller, so you might eat less and lose weight more easily. Staying hydrated also helps you control your appetite, improve your energy and sleep, and support your digestion. If you're using certain weight loss medications like GLP-1 drugs, drinking plenty of water is extra important to avoid dehydration and related side effects.