It shouldn’t surprise me that there is so little public interest or research pertaining to proper hydration. I suppose it’s like oxygen in the air. You breathe as much as you need and if you’re concerned with anything, it’s the pollutants. Likewise you drink when you’re thirsty, and only concern yourself with the temperature, sugar, caffeine, or alcohol content of your drink.
Admittedly, there is little research to support the effect of hydration on exercise, weight loss, etc. So we’ll start with what we know, then extrapolate the impact of hydration on your fitness goals.
First of all, your body tissues are 50-75% water depending on whether we’re looking at bone, muscle, or uhm, guts. So on average you’re 65-70% water overall. And on a daily basis you’ll lose 5-10% of your water. That said if you sat around in your living room with the express goal of seeing how long you could go without water, you’d be dead within 10 days; closer to 3 days if you do the test outside in the summer. The lesson here is you can’t conserve it. You certainly can’t make your own. So water has to be replenished.
How much water do you need? Good question! Let’s do the math. Say you weigh 120lbs. It’s a hot day. But you’re not particularly active. So we’ll say you lose 7% of your water during the day. 68% of 120lbs is 81.6lbs. 7% of 81.6lbs is 5.7lbs or roughly 90oz. That’s 90oz of water lost over the course of the day by just sitting around. So you’ve got to make it up, right?
What effect does not getting enough water have on your metabolism? This is where it gets interesting. We all know you’ll get something to drink before it gets dangerous. But as little as a 2.5% loss of water is equal to a 25% loss in efficiency. So when exercising you’ll quickly notice fatigue, reduced mental alertness, and reduced cardiovascular function. In short, if you’re dehydrated you probably won’t want to workout. And if you do, you won’t be able to perform at your best. This is important to take into consideration because the more work you do the more calories you burn.
What are the effects of staying well hydrated? This is where the research gets a little thin. I would hypothesize that if the research suggests a loss of mental alertness and reduced energy is associated with dehydration, then proper hydration should make you more alert and increase your energy. But don’t take my word for it. If you do a web search for the Thermogenic Effect of Water (I did) you’ll find a study that appeared in the Journal of Clinical Endocrinology & Metabolism that found a 30% increase in metabolic rate in subjects after consuming 500ml of water. Pretty impressive when you consider the usual thermogenic aids you hear about are caffeine and ephedra.
On a side note, you should realize that you’ll be in the bathroom more if you stay well hydrated. It’s a hassle, especially if you sit in traffic as much as I do. But I think you’ll find it’s worth it. And on another aside, what if you drink too much water?! Somebody’s going to bring up water poisoning, or hyponatremia. It’s a legitimate concern, and a tragic way to go. But I found less then 10 published accounts of Americans drinking themselves to death (with water), ever! So I’m not saying it couldn’t happen, apparently it’s a genuine concern in hospitals. I’m just saying there are more than 20 times as many documented cases of spontaneous human combustion. And I bet you haven’t lost sleep over that.
By Arek Long MA, CSCS
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