Does Drinking Water Help Lose Weight? And 8 Other Hydrating Questions

Water does a body good, but is it really the miracle cure that some people claim? Here’s how drinking water really affects your body and your brain.

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Do I need 8 glasses a day?

Don’t go crazy refilling your Sigg; let thirst be your guide. How much water you need daily depends on your diet, size, and body chemistry.  Nobody really knows where the recommendation of eight glasses a day came from, according to a 2008 paper about water myths in the Journal of the American Society of Nephrology. Keep in mind that exercise blunts your thirst mechanism, meaning you may need to drink water before working out. Not a fan of water? Here are 7 other ways to stay hydrated.

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Does drinking water help lose weight?

Sipping water before meals may make you eat a little less and that can contribute to weight loss, although it’s certainly no magic bullet. However, Virginia Tech researchers found that people ate 75 to 90 fewer calories when they drank two cups of water right before a meal. Swapping sugary beverages for water is also a good ticket to a thinner waistline. (Weight loss is just one of the benefits of lime water for your health.)

Side view of black female athlete drinking water from bottle in the gym
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Can drinking water give me more energy?

In a 2012 Journal of Nutrition study, women found everyday tasks more difficult, had more trouble concentrating, and were more fatigued and irritable when they were mildly dehydrated. Bottom line: If you need a mental pick-me-up, go for a glass of the water before you sample a snack.

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Can you prevent headaches with water?

Some evidence suggests that not drinking enough water could trigger migraines, or make them last longer. One study in the Handbook Clinical Neurology found that migraine sufferers who drank 1.5 liters of water in addition to their daily fluid intake experienced 21 fewer hours of pain than a group given a placebo drug. If you’re prone to the excruciating headaches, it can’t hurt to drink more water with or between meals.

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Can water prevent heart disease?

Maybe. In a classic study of Seventh-day Adventists, those who drank five or more glasses of water had about half the risk of fatal heart disease than those who consumed two or fewer glasses. Researchers suspect even minor dips in hydration could make blood thicker and stickier, which may make it more prone to clotting. However, with studies like this, be careful about association versus causation, notes Reader’s Digest columnist Joel K. Kahn, MD, a cardiologist and author of The Holistic Heart Book. It’s possible that water drinkers had other habits in common that also lowered their risk, he notes.

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Does drinking more water prevent constipation?

Skimping on fluids is frequently blamed for slowing down digestion, but evidence suggests that drinking more only gets things moving for people who are very dehydrated, according to a 2010 paper in the journal Nutrition Review. In one study, the paper points out, increasing water intake by 50 percent didn’t have any effect in a group of children with chronic constipation, for example. While people with low fluid intake are at greater risk for constipation, it may be that other underlying factors—like a low-fiber diet—are the real issue.

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Can water help your body naturally detox?

If drinking more water helped us detox, it would likely be through improved kidney function. But this common claim doesn’t really hold up when you look at the science. “In fact, drinking large amounts of water surprisingly tends to reduce the kidney’s ability to function as a filter,” Stanley Goldfarb, MD, a University of Pennsylvania kidney expert, told National Public Radio.

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Will drinking water give me glowing skin, like supermodels claim?

Unless you’re severely dehydrated, drinking extra water is unlikely to affect your complexion. “If you get dehydrated, your body is going to pull water from your skin to maintain the concentration in your blood,” Richard Besser, MD, told This can make your eyes look sunken, and your skin appear older and more dry. “If you’re not dehydrated and you drink a lot of water, it’s just going to send you to the bathroom,” he said. As for people who swear by water’s anti-aging effects, drinking more of it likely means cutting out soda and other sweetened beverages that can age your skin. Here’s what actually happens to your body when you start drinking enough water.

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Can you overdose on water?

It is possible, but life-threatening dangerous overdoses often involve fraternity hazing or other deliberate attempts to drink huge amounts of water in short periods. When you drink too much water, your kidneys can’t flush it out and water saturates your blood. This excess water starts leave the bloodstream, entering and plumping up cells throughout the body. The problem, though, is when neurons in the brain begin to swell; constrained by the skull, they have precious little room to expand and this swelling can lead to seizures, coma, and death. Make sure you know these 9 signs that may mean you’re drinking too much water.

Medically reviewed by Elisabetta Politi, CDE, MPH, RD, on September 19, 2019
Reader's Digest
Originally Published in Reader's Digest