Does your body burn energy keeping cool?

31 August 2008

Question

Does your body burn more energy trying to keep cool than it would trying to warm up?

Answer

Sarah - This is linked to what I was saying before about thermo-regulating. Your body works best at a certain temperature around 37 degrees centigrade so when your temperature goes below or above that your body will try and reset it to its level at homeostasis. When you're too hot you do things like you sweat and when you're cold you shiver to warm you up. The simple answer is that it takes a lot more energy to warm yourself up because to do that with shivering it's kind of like going to the gym. It's the really fast contracting of your muscles that causes you to shiver. It's like going for a run or doing other sorts of exercise. Obviously that's going to take up a lot of energy whereas cooling yourself down through sweating is a much more passive process. It doesn't take that much energy from your body to pump the sweat out onto your skin so the air is sort of doing the work for us to cool us down. Ben - So as your sweat evaporates off your skin that takes the heat away from you, you're not having to actively remove the heat. Sarah - Exactly.

Ben - But Steve is in Dubai. Surely the processes that people go through in Dubai can't be the same as over here in the UK where, let's face it, it's not very warm.

Sarah - No. I think also not just the heat but the level of humidity in the air is quite important. If it's really humid so there's lots of water already in the air it's obviously going to be a lot harder for the moisture in your skin to evaporate so you will always feel hotter when it's humid than when it's dry. Ben - The same amount of sweating will actually lead to less cooling. Sarah - Yes, because the air is already too full of water for it to take much more from your skin.

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