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View Full Version : hot or cold? Metabolism question



WeirdAl
12-10-2002, 02:15 PM
Anyone know if your metabolism runs faster when you are hot, or when you are cold? I know a bunch of people bundle up and try to sweat the weight off, but as I'm not concerned with water weight, I think being cold would be more effective for losing fat, as I'd think your body would be burning more calories for warmth when you are cold, thus a higher metabolism and fat loss.

Anyone know for sure? Also, I'm wondering if spot coldness could possibly (don't think so, but who knows) method of spot fat reduction - the hypothesis being that local fat could be burned to combat local coldness. Again, I don't think so, just wondering what you guys think.

Harvey Balboner
12-10-2002, 02:27 PM
interesting theory, I don't have any idea if it would work or not though.

mbstrong
12-10-2002, 02:31 PM
This is just my .02 but when your body is cold your metabolism will slow down. Everything on the inside is moving slower.

BiggerStronger
12-10-2002, 02:41 PM
I would also agree that your metabolism slows down when you're cold.

WeirdAl
12-10-2002, 02:54 PM
Well, when I'm cold I shiver, and I think the biological reason for shivering is to cause heat. And my thinking is that your body wants to maintain a constant temperature. So, if the ambient is colder than your body temp, your body will have to create heat to maintain it's temp. And to create heat, you body has to burn calories.

But, I can also imagine your body slowing everything else down while you are cold, so maybe there is little or no net effect, or your metabolism is slow. I'd be really interested in hard data, though.

WeirdAl
12-10-2002, 03:55 PM
BTW, I know that cold blooded animals have their metabolisms slowed down by the cold, but I thought warm blooded animals (like humans) were not.

WeirdAl
12-10-2002, 10:18 PM
bump

nox
12-11-2002, 04:00 AM
Every mammel has a "thermal neutral zone" when the temp goes outside this range metabolism is raised. The larger the mammel the larger the zone.
If it goes above the upper critical temperature then evaporative cooling (panting and sweating) and behavioral thermoregulation (getting into shade) take over.
If it goes below the lower critical temperature then nonshivering and shivering thermogenesis, regional heterothermy (your hand and feet go cold), behavioral thermoregulation (curling up into a ball), and adaptive hypothermia (lowered body temp) take over.
Which one raises metabolism more, I'd go with shivering cold over dripping with sweat. I just included the technical terms for fun, I'm not trying to be a elitest egghead.

bjtheman
12-11-2002, 09:29 AM
Even if your body is trying to warm up being cold it only tries to keep your body's temp normal! When the temp rises and the body's temp rises is when your metabolism speeds up!
Just like clen, or eca...those speed you and and even heat up your body!

hostile
12-11-2002, 10:42 AM
I hate cold!! Bump!!

WeirdAl
12-11-2002, 10:52 AM
found something to support nox's comment:

Endotherms have three distinct types of thermoregulation. At room temperature, the mice used in lab have a normal metabolic rate, and this range of comfortable temperatures is called the zone of thermoneutrality. If the air temperature were lowered significantly, the mouse would begin to shiver (raising the metabolic rate) to maintain body temperature. The point at which shivering starts, and the lowest air temperature that the animal can withstand is determined by the amount of insulation (fur and fat). If the air temperature were raised above comfortable levels, the mouse would also, seemingly paradoxically, raise its metabolic rate as it works to cool itself. Mice can not sweat like humans, so they must cool themselves by panting (as dogs must also) to bring cooler air into the lungs. This is work, and causes the animal to increase metabolic rate. At some point the animal will die from overheating.

WeirdAl
12-11-2002, 10:54 AM
One thing interesting, though, is that in mice, the higher air temperature (from what I'm reading above) causes an increase in metabolism due to their inability to sweat, and need for panting. So I'm still not convinced that being hot will increase the metabolism in humans (who can sweat).

rugbythug
12-11-2002, 10:57 AM
I read once-for every degree your bodytemp rises you increase your metabolism %7. When you get cold your body starts slowing down non vital systems. Ever notice that people from cold climates are usually fatter than people in hot climates? Other reasons are also present but this is one of them. Ever notice that you are slimmer in the summer than winter?

intense
12-11-2002, 12:15 PM
Think of it this way.

You body wants to remain at say 96 degrees temp.

You start to jog in hot weather and it raises to 100 degrees your body attempts to cool it off through sweating ect.. back down to its base 96 degrees.

In the winter the same thing still happens, you body is going to raise above its natural set point and your body will attempt to cool itself, only this time it has a more effective cooling system being that the surrounding air is much cooler.

You body does not dip so low below your heat rate needed for survival that on top of the excess heat created from cardio your body still needs to raise its tempeture to get back to normal heat. We arn't talking about spending the night naked out in the cold.

rugbythug
12-11-2002, 03:19 PM
98.6

rugbythug
12-11-2002, 03:21 PM
Think of yourself as a machine. Does your car run better warmed up and hot or cold? Everything is more efficient at a warmer temp. Including fat burning.

notacow
12-11-2002, 05:05 PM
Check out "Food for thought" in Scientific American December 2002.

While this article is mostly about how much more energy a human uses for his brain, and how it evolved that way, they do mention many basic metabolic facts.

Generally a 'people' who live in a colder climate have higher matabolisms. There are some reindeer herders in siberia, called 'Evenki', where a 125 pound man uses 3000 cal a day!

Just because the US has a bunch of fat white people living in the north does not negate this hypothesis. That just means they have money and McDonalds. Eskimo's use a lot more energy than we do, and not because they shiver all the time.

As for local coldness causing local fat reduction. I Don't Think So.

If you're warm, turn down the thermostat. If you're cold, take more T3. :D