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How many calories do you burn when you're cold?(7 posts)

How many calories do you burn when you're cold?PdxMark
Oct 14, 2003 4:07 PM
It seems like we should/would burn extra calories when we're cold. There are of course a huge number of variables in determining just what being cold is, including how wet/dry someone is, the amount of insulation (clothing) they have, wind chill, etc. But is there any rule of thumb or information about how many calories are burned due to being or feeling cold?

At the extreme, there ought to be the hypothermic limit at which we can't generate enough heat to stay warm. That ought to be the maximum heat generating rate, and it should have a calorie burn rate associated with it. Being subjected to temperatures that dissipate heat faster than that heat generating rate would result in hypothermia.

At lesser levels of being cold, it might be too hard to measure... Does anyone have any information or resources?
Pretty hard to estimateKerry Irons
Oct 14, 2003 4:46 PM
For example, if you are dressed warmly, then your body doesn't know from cold. Your body could be in a micro climate that is just like a summer's day. OTOH, if you are constantly dropping in core body temperature, you're headed for a "zero calorie burn state" - AKA dead. In between lies the territory where you might be burning more calories to keep warm. The only thing you can be sure of is that when you are shivering, all of that calorie expenditure is going to keep you warm. After all, even in fairly cold conditions, you still find yourself sweating some, which suggests that your body is producing excess heat - more than enough to keep your core warm. It's a whole lot more about how much work you're doing than what the temperature is.
Pretty hard to estimatePdxMark
Oct 14, 2003 5:07 PM
The microclimate thing (e.g., a down parka) is the huge variable. Hmmm. I could imagine an interesting research project if I had $100,000 to give away as a grant.

Is it true that calorie burn rates can be measured during certain aerobic tests - such as by monitoring what a person exhales over time? If so, it seems one could test each test subject at different ambient temperatures (and different activity levels) while they wore just a swimsuit. Stepping down in 10 degree(F) increments for inactive, slightly active, and very activity levels. Heck, toss in a fan as yet another variable... (it wouldn't cut too much into the $100k grant).

The US military must know this, or something like it... and I bet they spent lots more than $100k to get the information. Or maybe it's not that interesting a question.
Pretty hard to estimatefiltersweep
Oct 14, 2003 5:59 PM
It is an interesting question- my HRM gives me its opinion how many calories I've burned based solely on HR, but it doesn't account for heat generated. Of course, activity itself seems to correlate with generating heat.

One issue is that our entire body doesn't necessarily stay entirely warm- we may have cold hands or feet or whatever, and my guess is, unless the HR is elavated a bit to increase circulation, the body just runs a bit cooler than it might under other circumstances- and most people will do something else to warm up- like add clothes, turn up the heat, head indoors, etc... so I doubt we burn significant energy staying warm unless we are shivering or more active.
Technical Term is Adaptive Thermogenesis...Mr Nick
Oct 14, 2003 7:24 PM
And it is the fourth variable in calculating total energy expenditure. The other three include basal metabolic rate, physical activity and thermic effect of food. There are no direct calculations to account for adaptive thermogenesis that I know about. It is taught that adaptive thermogenesis is a small aspect of total energy use unless you are in really severe conditions. For most people in normal conditions physical activity is the most variable factor effecting total energy expenditure and therefore the only thing that should really be worried about.
Thx for the term... what about hypothermic conditions?PdxMark
Oct 14, 2003 9:01 PM
It seems that it would be small (negligible?) only so long as you are dressed appropriately & dry. Or maybe being wet & cold, in pre-hypothermic conditions, really doesn't burn many calories.

In hypothermic conditions, you are supposedly losing heat faster than your body can generate it. That means that the adaptive thermogenesis ought to rise a bit in the pecking order, right?

Though, in really cold water situations, a person's survival time can plummet if they try to swim even a short distance, rather than stay where they are. Physical activity plus extreme cold can drop the base temperature very quickly relative to extreme cold alone. One reason would be that the swimmer is movely freshly cold water over his body. Is there a physiological action going on too?
Hypothermic ConditionsMr Nick
Oct 15, 2003 8:37 AM
Usually hypothermic conditions occur whenever the body can not maintain the proper core temperature. Being submerged in water is the easiest method because you are completely surrounded by something that is stealing heat. Theoretically you could go into hypothermia in 80degree water if you submerged yourself in it long enough, because it is colder than your core body temperature and heat is flowing from you body into the water. The reason you cut your surivival time with movement in the water is that it takes quite a bit of energy to perform physical activty and if you add this onto the heat disipation into the water you are just burning energy like crazy.

If you are really interested in energy expenditure due to temeprature and its effects on exercise performance you should do some research on mountain climbers. I am sure they have data looking at the energy loss due to extreme cold, because when you climb mountains such as everest, things like elevation and temperature play a huge factor in caloric need and total energy expenditure.