9 Weird Things Dehydration Does To Your Body
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I am convinced Bikram yoga would kill me. I’m just too sweaty.
I can produce a puddle of sweat under a spin bike that a small child could swim in. I don’t wear gray. I was poked and prodded by doctors who thought there could be an underlying thyroid problem to explain my drenched T-shirts. But no, every expert came to the same nonmedical, totally unhelpful conclusion: I am a sweaty person.
It took me a while to be anything but embarrassed by my tendency (being bestowed the nickname “Sweats” by my soccer teammates certainly didn’t help). And before I had learned to just accept my sweatiness or risk never lifting my arms above my head again, things got a little scary.
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The first time I got seriously dehydrated, I was just trying to make varsity. A week of two-a-day high school soccer tryouts terminated in a scrimmage one particularly hot August afternoon, and by the end of the game I had stopped sweating and lost all the color in my usually flushed face. Eventually, my cramping legs buckled as I tried to get out of my dad’s car in our driveway.
Mix dehydration with high temps and you’ve got a pretty perfect recipe for heat illness, an experience I am eager not to repeat. I had to learn the signs my body’s water tank was running low: a scratchy, salty film that dries on my face; feeling cool in the middle of a 90-minute game in the summer. Seriously, I should buy stock in Gatorade.
I focused so much of my energy on not getting dehydrated while exercising that I didn’t realize until pretty recently (even though I love writing about all things sweat so much I have dubbed myself the captain of the made-up #teamhydration) that many of us—yes, you normal sweaters, too—walk around at least slightly dehydrated on any given day. “Your body depends on water intake, but most people don’t drink enough,” says Stavros A. Kavouras, PhD, a hydration and fluid balance researcher, associate professor, and coordinator of the Exercise Science Program at the University of Arkansas, who owns the Twitter handle @DrHydration, which might make him the actual captain of #teamhydration.
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Luckily, while it can have health effects, this type of mild, daily dehydration isn’t usually a health concern. Typically it just takes a nice cold drink of water or even a hydrating snack, like watermelon or cucumber, to reverse the damage.
But severe dehydration can cause your entire body to malfunction. And when it’s freaking hot out, you don’t have to be running a marathon to be at risk. Even just spending an afternoon outside can leave you dripping, and if you’re not replacing what you’ve lost, no matter what activity you’re up to, you could be setting yourself up for trouble.
It’s all about balance, says Lawrence E. Armstrong, PhD, a professor and interim department head in the kinesiology department at the University of Connecticut who studies dehydration, fluid balance, and heat tolerance. “The entire amount of water in a woman’s body may be 38 to 45 liters, and for a man, 42 to 48,” he says. “Dehydration means that for a period of time, you have lost part of that water. It’s a matter of whole-body balance.”
Because no one is volunteering to wring out the shorts of sweaty gym-goers, dehydration is typically measured instead by the percentage of your body weight you’ve lost, he says. I’ve tested this out a couple of times by weighing myself before and after going for a run, and I have to admit I’m always pretty impressed by my sweating ability. Here’s how it works: At the start of your workout, say you clock in at 150 pounds. You head out for our 45-minute sculpting walking workout, and when you come back you’re 2 pounds lighter. It would be nice if weight loss worked that way…but those 2 pounds are probably water weight. They’re also about 1.3% of 150 pounds. If you’ve lost between 1 and 2% of your body weight, you’re mildly dehydrated. If you’re down between 2 and 4%, you’re moderately dehydrated. Things start to get serious after 5%. Your kidneys fail after losing 11% and you could die if you lost 15 to 20%, according to Armstrong.
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So what’s actually going on in your body when you’re slowly losing your liquid life force? Before we get all scientific, a request: Please seek emergency medical attention for anyone you think is dehydrated who loses consciousness, has a fever higher than 102°F, becomes confused or less alert, or shows symptoms of heatstroke like rapid breathing or pulse. This also goes for anyone who gets worse despite having stopped their activity, moved to the shade, and had something cold (and nonalcoholic, hello!) to drink. Now here are a few of the biggies.
Dehydration makes it hard for your body to control its temperature.
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Every little movement you make generates heat in your body, but our core temps actually stay stable, says J. Timothy Lightfoot, PhD, director of the Huffines Institute for Sports Medicine and Human Performance at Texas A&M University. That means your body’s working to keep things steady by releasing heat through processes like sweating: When sweat evaporates from the skin, it takes some of the heat along with it.
But when you’re dehydrated, you don’t have enough water inside to sweat any out, which means you miss out on that brilliant built-in cooling mechanism, too. The heat stays trapped in your body, and your core temperature continues to rise.
Should it get too hot in there, you’re at risk for heat stroke, which can, frighteningly, be fatal. Luckily, heat stroke itself is pretty rare, Armstrong says, especially if you stop what you’re doing at the first signs the heat is too much, he says.
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That’s right, you can stop sweating.
For people like me, it’s pretty dang obvious. One minute, little rivulets will be trickling down the sides of my nose; the next, the flow has slowed and there’s a film of dried sweat across my cheeks, despite the fact that I’m still running. Not good, Lightfoot says. “This is the body trying to regulate; we don’t have enough fluid to both sweat and pump blood to the muscles, so it starts selectively shutting down some processes. When your body is trying to provide adequate blood flow to your muscles and provide enough fluid to sweat to remove some of the heat, sweating will lose.”
Same deal if you turn a ghastly shade of gray: “That’s the body saying, ‘I need that fluid elsewhere,’ so it shuts off the blood vessels in the face,” he says. This is—thankfully—pretty extreme, Armstrong cautions. The average person going about their daily business won’t stop sweating from a little mild dehydration, he says.
Your heart has to work overtime…
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About 60% of the human body is water, and one of the biggest reservoirs we’ve got is our blood, Lightfoot says. When you start to get dehydrated, your blood volume decreases, but your heart has to pump the same amount through your body to provide the same cooling relief and the same nutrients to working muscles, he says. “Reducing the volume available makes the heart work harder.” When your heart can’t keep up, you could be at a greater risk of heat exhaustion, Armstrong says, a less dangerous cousin of heatstroke.
To maintain steady blood pressure with that decreased volume of blood, your vessels constrict. This tightening may be why some people experience dehydration headaches, Lightfoot says. (Learn how to lower your blood pressure [without drugs!] here.)
…which means you can physically do a lot less.
Carrying the first potted plant to the backyard garden may feel like a piece of cake, but by the fifth, the sun beating down on you the whole time, you suddenly feel like you’re carrying a 50-pound boulder. “A workload that may not be strenuous at first becomes very, very strenuous,” Lightfoot says about being dehydrated. If it feels like it takes a much greater effort to keep up the same old task, it’s essentially your body trying to tell you to lay off because it can’t keep up, he says.
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You get toddler-level cranky.
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Ever feel forgetful, confused, mentally sluggish, whiny—then suddenly realize you’re thirsty? Our brains don’t like being low on liquids, although researchers aren’t entirely sure why that can lead to a hissy fit, Armstrong says. One (disturbing) theory is that specific areas of the brain physically shrink when you don’t have enough fluids in you, Kavouras says.
Armstrong’s research has shown these symptoms can start pretty early on in the dehydration process, too—and that they affect men and women differently. In one study, women noticed their moods dropped, tasks became more difficult, and they had headaches and a harder time concentrating after losing just 1.36% of their body weight after some treadmill walking. In another, men reported feeling tense, anxious, and fatigued and noticed their memory slipping after losing just 1.59% of their body weight.
Your pee won’t look like lemonade anymore.
If you can even go, that is. A severe loss of fluids may make a bathroom break impossible, but if the result in the toilet bowl is dark yellow, you should be concerned, and if it’s brown or reddish in color, you need to get yourself to a doctor. “If you can see that your urine is very concentrated, that indicates your body’s fighting dehydration,” Kavouras says. Taking a peek at your pee is about the easiest way to tell if you’re dehydrated, since very few other measures provide effects you can physically see. You don’t want to be going every 15 minutes, but if you’re hitting the head fewer than 5 or 6 times a day, you’re probably not getting enough H2O.
You lose salts—and might need to replace them.
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If you, like me, are familiar with that chalky film on your face after your workout’s over, you’re seeing firsthand the salts we lose in our sweat. It’s why sports drinks try to sell you on their electrolytes. Most of us are probably fine replenishing our liquid tanks with water, though. “The average 20- to 30-minute workout doesn’t warrant a sports drink,” Armstrong says. Just make sure to get some fluids back in before you’re really thirsty, Lightfoot says.
It is worth taking along a sports drink to replenish your salt and potassium on a tough sweat session, though. Think 70% or greater of your maximum effort, for longer than an hour, which, let’s face it, is not your average workout (nor mine!).
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Speaking of which, yes, you will get thirsty.
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Yes, this is a bit of a no-brainer. But! We actually don’t get thirsty all that easily, Kavouras says. Water wasn’t always readily available to our hunter-gatherer ancestors, so we’re programmed to survive without it for a significant amount of time; thirst kicks in when we’re already in a bit of a water deficit, he says.
Which naturally leads us to the age-old conundrum: How much water are we really supposed to drink?
Sorry to break the unsatisfying news, but there’s really no one-size-fits-all recommendation. The Institute of Medicine estimates men need about 3.7 liters a day and women need about 2.7, but that includes the fluids we get from the foods we eat, which accounts for roughly 20% of our daily water intake. “The most honest answer to the question of how much water you should drink is 'it depends,’ ” Kavouras says, on everything from the weather to how active you are to how high you have your AC cranked.
Since most of us won’t sip it unless it’s right there in front of us, keep a bottle by your side in the office, he says. “Increased water intake is a very inexpensive way to improve your health.” At the very least, refilling it is an excuse to get up from your chair.
So, how do you know if you’re dehydrated?
Since I’m not Serena Williams or LeBron James, my next bout of heat cramps is unlikely to be treated by my own personal team of hydration experts. I’m on my own for summer 10Ks and recreational soccer games—clinical hydration tests simply aren’t accessible to us weekend warriors. Which is why Armstrong says to keep a watch on three of the factors we’ve discussed above: urine color, thirst, and body weight. If just one of these is off-kilter, you’re probably OK. But if two out of three are, it’s likely you’re low on H2O. And if all three are, it’s pretty certain you’re dehydrated. See you at the water fountain, team!
By Sarah Klein
This article ‘9 Weird Things Dehydration Does To Your Body’ originally ran on Prevention.com
