That's Fit

For most of us, it's getting warmer out, and for many of you that probably means long runs, walks, bike rides, and hikes. Some of you are also probably gearing up for race season -- there are some fantastic marathons coming up, as well as halfathons, triathlons, 10Ks, etc. All of this means that you're going to need to drink lots of water.

But wait! If you've been here at That's Fit for a while, you've already read that drinking too much water during exercise can be harmful, even fatal. It's a serious issue that warrants revisiting as the summer sun starts heating up.

Over-hydration, or hyponatremia, occurs when you take in more water than your kidneys can excrete because you've been sweating out lots of salt and you're replacing it with plain water (which is why sports drinks are used during long-distance runs and major workouts). Unless you're embarking on a serious workout, like an endurance race or a long hike, you'll probably be fine, but listen to your body -- make sure you're drinking plenty of water to stay hydrated, but not too much. Check out this post on FitSugar for warning signs of hyponatremia.

Have you ever seen the guys in the gym that carry around gallon jugs of water? Do they know something the rest of us don't? Is a drought coming or something? Or could it be that drinking more water actually burns calories?

The answer to this question is Yes and No. German researchers found that drinking 500 milliliters of water (about one pint) increased resting metabolic rate by 25 percent (which pretty much works out to be 20 extra calories for 60 minutes). Water ostensibly increases calorie-burning by diluting the blood flowing to the liver and by activating the sympathetic nervous system. This activation leads to an increase in caloric expenditure. So ... that was the Yes part of the answer.

The No part of the answer is that the amount of calories you burn by drinking an excess of water is negligible. To put it in perspective, you can burn 20 calories washing your dishes. In addition, drinking too much water can be dangerous, as it may cause hyponatremia, which can be fatal.

When it's all said and done, my guess is that the guys toting the gallon jugs of water at the gym are just plain thirsty (and smart enough to know that the water coming out of the fountain, unlike the water in their gallon jug, is likely filled with chlorine).

As much preaching as we all hear about not drinking enough water and how most people live life chronically dehydrated, it's interesting to know that it's possible to drink too much water -- especially when exercising -- and more people do it than you might think. Endurance exercisers are the only ones really at risk, and the problem (called hyponatremia) happens when you drink in more water than your kidneys can excrete. Potentially fatal, it's not something to take lightly, but it is easy to avoid: just respect your own personal "thirst" meter and drink only when your body says you need to.