How drinking more water may help you lose weight

Water does more for the body than just quench your thirst. Here’s how it might even help you lose weight.
Published November 25, 2019 | Updated July 10, 2024
A person's hand holding a clear glass of water, with a shadow on a turquoise surface.A person's hand holding a clear glass of water, with a shadow on a turquoise surface.

For such a no-frills substance, water sure has a lot of buzz surrounding it. Wellness gurus claim the more you drink, the bigger the health benefits: better cognitive function, improved blood circulation, and even bigger fat burn. But does that weight-loss claim hold any water?

Can drinking water help you lose weight?

There’s no directly proven link that drinking water leads to weight loss, but the clear, calorie-free liquid plays a role in just about every bodily function, including metabolism. (After all, 60 percent of your body is made up of water.) Reaching for good old water to stay hydrated can only help you on your journey to lose weight.

Does drinking water help decrease appetite? 

Research is scant here, but there is anecdotal evidence that water can curb your appetite — possibly because some people mistake hunger for thirst, which is triggered by mild dehydration, according to Dr. Melina Jampolis, M.D., a California-based internist and board-certified physician nutrition specialist. It almost goes without saying, but if you’re always grabbing a snack when what your body actually needs is water, you might find yourself on a path to weight gain instead of loss.

Drinking water before consuming a meal may help you feel full and eat less. One small study of adults with obesity found that those who drank about two cups of water before dining for 12 weeks lost nearly three pounds more than those who didn’t have water before eating.

At the very least, proper hydration can promote feelings of satiety, since fluid helps food move through your GI tract during the digestion and absorption process, and helps send the “I’m done” signal to your brain, says Jampolis.

Does drinking water boost metabolism?

In theory, yes, the chilly temp of a beverage may contribute to a temporary metabolic increase from thermogenesis — or heat production—since your body has to burn calories in order to warm fluid to body temperature. But the effect is more of a slight nudge than a big boost, and it doesn't have much impact on your overall calorie burn or ability to lose weight.

Still, if a handful of ice cubes gets you to drink more water, go for it. “Even if the effect is negligible, it is important to stay hydrated,” says Elizabeth Huggins, RDN, a dietitian at Hilton Head Health.

Will drinking water help me burn fat?

There are several studies looking at animals that show taking in more water can stimulate lipolysis, the process that burns fat for energy, and some researchers think the effects could be similar in humans.

“We’re not certain of the mechanism, but mild dehydration decreases lipolysis, which may be due to hormonal changes,” says Jampolis, who read the study but wasn’t part of the data-review team.

Another credible theory: Water expands cell volume, which could play a role in fat metabolism. Still, research needs to be done on actual people before Jampolis will recommend drinking more than the daily recommended amount of water.

Could drinking water help reduce your overall liquid calorie intake?

Filling your glass with flat or sparkling water instead of juice, soda, or sweetened tea or coffee is an instant calorie saver. Need an example? When you opt for water over a 20-oz bottle of sugary cola, you’ll drink 250 fewer calories, says Huggins.

Does drinking water increase the effectiveness of exercise?

When you add workouts to your weight-loss plan, you probably want that effort to pay off in more calories burned and more lean muscle mass. Hydration makes that happen.

Your body uses water to dissolve and distribute electrolytes to your muscles. Electrolytes are electrically charged minerals — including sodium, potassium, and magnesium — that trigger the contractions required for movement. Even mild dehydration can lead to an electrolyte imbalance and cramping, notes Jampolis.

“When muscle cells are dehydrated, the process of building muscle is slowed, making your workouts much less effective,” says Jampolis.

It’s also important to pay attention to hydration during exercise, because the body loses fluids as it generates heat and cools itself through perspiration. Drinking up helps your body maintain its blood volume, which allows blood vessels at the skin’s surface to expand and regulate body temperature, according to Jampolis.

“If your body can’t dump excess heat via sweating, you’re setting yourself up for heat exhaustion or worse,” she says. “Adequate hydration can improve your workouts by decreasing fatigue, which can allow you to work out longer and potentially burn more calories.” This means it’s a good idea to hydrate before and throughout your workout — not just when you start to feel thirsty.

Does drinking water reduce bloat?

Water helps everything move through your digestive system, so it’s reasonable to assume drinking more water would help prevent constipation — one of the major causes of belly bulges and bloating. But there really isn’t any solid research to prove it.

Does drinking water affect your motivation?

In addition to muscle cramps, dehydration leads to several annoying-to-scary symptoms that could zap your motivation to get moving, including fatigue, dizziness, and confusion. “Any of these symptoms could affect your motivation to exercise, cook at home, and make better food choices,” says Jampolis.

4 other health benefits of drinking water

Drinking water to lose weight might be a priority for you, but it’s not the only reason to keep sipping. Here are a few more ways water supports your health and wellbeing.

1. Water may help boost your brainpower

Just like the rest of your body, your brain depends on water to work well — it’s actually made of 73 percent water. Research shows even mild dehydration (as little as two percent water loss) can impair your performance on tasks that require attention, cognitive functions and physical movement, and immediate memory skills.

2. Water regulates blood pressure

“Water plays a major role in keeping the blood flowing effectively,” says Huggins. “When you’re dehydrated, the plasma/blood cell ratio changes in a way that makes the blood thicker and more viscous. This makes it tougher for blood to flow where it needs to flow, increasing the stress placed on the heart.”

What’s more, when your body’s cells don’t have enough water, your brain pumps out a chemical that constricts the blood vessels. Research shows this can lead to hypertension or high blood pressure and can increase your risk of stroke and heart disease. Staying hydrated prevents your blood vessels from constricting so blood can flow normally.

3. Water helps remove waste

Drinking water keeps solid waste moving through your digestive tract, and helps it all come out more easily — meaning, you may be less likely to be constipated or experience pain from too-hard poops. But staying hydrated does more than just soften things up, it also helps to restore electrolyte balance and ease bowel discomfort after a bout of too-loose stool or diarrhea.

Not only that, but your kidneys need water to help filter out toxins and other waste from your bloodstream, which is then flushed out of your body when you urinate.

4. Water aids digestion

Drinking water with meals, snacks, and anytime you’re thirsty helps your body break down and digest food into absorbable nutrients.

So, how much water should you drink?

It’s common to aim for eight glasses of water a day, but you might need more. The amount of water someone needs can vary based on age, biological sex, health, physical activity, tendency to sweat, and more. That’s why the National Academy of Sciences, Engineering, and Medicine (NASEM) recommends 91 ounces (about 11 cups) a day for women and 125 ounces (about 15.5 cups) for men.

That said, according to NASEM, most people can “adequately meet their daily hydration needs by letting thirst be their guide.”

A quick way to see if you’re hydrated or not? Look at the color of your urine. “If it’s dark yellow, you aren’t drinking enough,” says Jampolis. “Aim for light yellow.”

The bottom line

Along with making healthy food choices and getting regular physical activity, drinking water for weight loss is a great habit to get into.

Switching from beverages that contain calories to water can help you reach and maintain your weight loss goal, and staying hydrated helps your body run more efficiently. “Water is critical in every cellular activity of our body and helps us feel better,” says Huggins.

Still, drinking water for weight loss should only be one small part of your wellness plan. It’s important to embrace a more comprehensive approach for total well-being, notes Jampolis.

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