Hydration Dos and Don’ts

Your car will conk out if you don’t top off the fluids -- and your body is no different. But making sure you stay well hydrated can become a challenge when you start a new exercise regimen. That’s because your daily fluid requirements rise by 25% to 30% when you get up off the sofa and increase your physical activity.

Keeping your fluids in balance isn’t only necessary for a great workout, but it's essential for sound overall health, says Amy Kimberlain, RDN, a nutritionist at Baptist Health South Florida in Miami. “Good hydration keeps all your biological systems working well,” she says. “And you just feel better.”

Here are some dos and don’ts that can keep your engine running with the right fluids.

DO make water your go-to beverage for staying hydrated.

At least 60% of your body is made up of water, says Kimberlain, who’s also a spokesperson for the Academy of Nutrition and Dietetics, but you lose some throughout the day when you go to the bathroom, perspire, and even breathe. “We need to replace that water in order to keep our bodies working properly.”

Your daily water loss increases dramatically when you hit the treadmill or take an aerobics class. Picture a liter-size bottle of water. If you work out vigorously for an hour, your body loses at least that much water and possibly more, mostly through sweat, says physiologist Luke Belval, PhD, a post-doctoral research fellow at the Institute of Exercise and Environmental Medicine at Texas Health Presbyterian Hospital of Dallas. “Drinking water replaces the main thing that you lose during exercise,” says Belval, who’s also an expert on hydration for athletes.

DO tailor your water intake to your individual needs.

But how much water do you need after a workout and throughout the day? The old advice to drink eight glasses of water daily isn’t based on science. For starters, that’s too low. A typical woman might require 9 cups of water daily, while a man needs 12.5 cups, Kimberlain says. Some portion of that can come from other beverages, including coffee and tea, which, despite what you may have heard, don’t “dry you out” and do have a net hydration benefit.


The amount of water you should drink a day is highly individualized and depends on several things, Belval says. For example, a glance around any crowded gym confirms that some people sweat more than others. If you exercise outdoors on a hot day, you’ll lose more water than if you’re in an air-conditioned gym.

To decide how much water to drink and when to fill up, Belval says to follow another piece of advice: Let thirst be your guide. “Thirst is a really good indicator of whether or not you need more water,” he says. That’s because thirst is a mechanism your brain triggers when it senses that the concentration of water in your blood has dipped too low.

But there are some exceptions to this rule. During exercise, your brain’s thirst mechanism doesn’t work as efficiently, Belval says, so it makes sense to keep a water bottle handy and take sips now and then. Also, as you age your thirst detector may become less sensitive, which is a good reason to drink water throughout the day.

DO watch out for dehydration.

Belval has a simple test to see if you’re getting enough water from day to day. You can remember it by the acronym WUT, which stands for weight, urine, and thirst. If you check two of these three boxes, you may not drinking enough.

  • Weight fluctuations: Get on the scale when you wake up every morning. If you lose a pound or more overnight, and you exercised for an hour the day before, that could mean you didn’t replace the water you lost, Belval says.
  • Urine: Check the color of your pee. It should look like lemonade. If it’s more like apple juice, that’s a sign of dehydration.
  • Thirst: Waking up parched every day is a telltale sign that your water tank is low.

Other signs of dehydration include headache, fuzzy memory, and cranky mood.


DON’T bother with pricey “workout” water.

You may have seen pricey bottled water infused with electrolytes in a convenience or nutrition store. Electrolytes are minerals like sodium, potassium, and calcium that play a variety of critical roles in your body, such as keeping a steady balance of water in your system. Companies that sell these products say since your body loses electrolytes during exercise, it’s important to drink water and other beverages spiked with these minerals during a workout to boost performance and stave off fatigue. But that’s only true if you work out at high-intensity for over 90 minutes, Belval says. During shorter workouts, the amount of electrolytes you lose is low and easily replaced by the food you eat.

Likewise, you don’t need so-called “recovery” beverages, which are laced with protein and other additives. They’re really for serious bodybuilders, who break down muscle during long weight-lifting sessions. For everyone else, they simply add calories, which can wreck your weight loss efforts.


DO make water more interesting.

If you get bored with water, liven it up by adding a few cucumber slices or sprigs of mint, Kimberlain says. It also won’t hurt to add a splash of fruit juice for a touch of flavor and color.  

DO try sports drinks, but only for long workouts.

Let’s say your get-in-shape campaign is a rousing success and you find yourself fit enough to join an adult soccer league or take daylong rides with a cycling club. When you exercise for 90 minutes or more, your body’s fuel levels drop and fatigue may set in. Swigging a sports drink -- which usually has carbohydrates in the form of sugar, a source of energy -- can help keep you in the game. You don’t need a sports drink for shorter bouts of physical activity, Belval says. Water will do just fine.

DON’T drink fruit juice, soda pop, or caffeinated beverages before a workout.

Once you start moving, fruit juice can upset your stomach. It’s also a rich source of glucose, a type of sugar, that slows your body’s ability to absorb fluids. The same goes for sugary soda, which is also carbonated and can make you feel bloated. That might end a workout early. Both contain calories, which won’t help if your goal is weight loss. (Diet soda isn’t a good option either, since it has been linked to obesity.) Having caffeine before you exercise can burn up fats in the blood, Belval says, but it also boosts your heart rate, which could make you too jittery to jog.

WebMD Feature


Amy Kimberlain, RDN, CDE, nutritionist, Baptist Health South Florida; media spokesperson,  Academy of Nutrition and Dietetics, Miami.

Luke Belval, PhD, post-doctoral research fellow, Institute of Exercise and Environmental Medicine, Texas Health Presbyterian Hospital of Dallas.

Cleveland Clinic: “Drink Up: Dehydration is an Often Overlooked Health Risk for Seniors.”

Rush University: “Essential Electrolytes.”

The Yale Journal of Biology and Medicine: “Gain weight by ‘going diet?’ Artificial sweeteners and the neurobiology of sugar cravings.”

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