Does the ambient temperature affect the number of calories burned, and if so, how? When it’s 70F outside and I walk for an hour, it seems a lot easier than when I walk the same path at the same speed at 90F. According to the tables, all that matters is the speed and duration. So why do I feel more tired when it’s hot? Does the amount I sweat have any effect on the calories burned?
Is there a simple and relatively accurate method of calculating the calories I burn in an activity that doesn’t appear in any of the usual tables? As some here may know, I drive my sports car on racetracks. This is much more strenuous than ordinary street driving, and I’d like to know how much more.
According to what I’ve found online, the amount of calories burned is figured by measuring oxygen consumption, which I assume involves fancy lab equipment. Is there any way I can get a reasonable ballpark in the field without a significant investment? Could I correlate my heart rate somehow?
The harder your body works to cool or warm itself the more calories are burned. At room temp, you burn fewer calories than you do when it is hot or cold. The farther from the ‘comfortable’ temp of around 68-72 you get, the more calories you burn.
Your heating and cooling system needs calories. Sweating is not pushing out cals, but the fact that you face conditions requiring you to sweat is an indication the body is working harder to cool itself…and cals are burned in doing so. Same deal for heating up your frigid body.
I have never seen anyone able to provide a cite for the proposition that the body’s cooling mechanisms use any significant calories. Many have tried to support this proposition but none have succeeded so far. I suppose there must be some theoretical calories used in opening up capilliaries and sweat glands, but if anyone’s been able to measure it, I’m yet to see a cite that says so.
Wha? The sweat means your body has opened sweat glands to increase evaporative cooling. It is not an indication of any significant work being done.
Possible but unlikely if you are walking hard and appropriately dressed. Human metabolism is pretty inefficient (about 40%) . Most of the calories burned end up as waste heat. If you are exercising, unless you are somewhere really cold, or underdressed, you will produce plenty enough waste heat that your body need burn no additional calories just to stay warm.
I found that most of the tables, formulas, etc. were totally inaccurate for my cycling, so I did a little research and found heart rate based formulas in the journal article “Prediction of energy expenditure from heart rate monitoring during submaximal exercise” published in the March 2005 Journal of Sports Sciences.
The first thing I noticed is that their model predicted about half the calorie burn as indoor cycles at the club or my cyclecomputer. But after tracking food consumption and weight loss over time, I found that it provided a much more accurate estimate.
Maybe you’re aware of that, but I’d like to mention it nonetheless: Whenever you compute something involving energy consumption and caloric value of food, you have to keep in mind that there’s a fundamental inconsistency about the usage of the terms “calories” and “kilocalories.”
The calorie, as a unit of energy, is defined as the energy needed to warm up one gram (about 0.035 fl. oz.) of water by 1 °C (1.8 °F). The “calorie” which is used to measure the caloric value of food, however, equals 1,000 calories and should be called kilocalorie, which it usually isn’t.
Thus, if you drink a 12 ounce/355 milliliters can of soda chilled to 5° C (41° F), warming up this to body temperature of about 37° C (98 °F) will cost your body 5 * (37-5) = 160 calories, but these are only 0.16 kilocalories. Thus, drinking large amounts of cold drinks will not, contrary to a somewhat popular belief, help you significantly to lose weight.
Well, according to this, heart rate and blood glucose and lactate levels are all higher when exercising at 33C compared to 17C. I think I read somewhere that the heart rate increase is partially because of the increase blood flow to the skin needed to make sweat and cool down the body, but the glucose and lactate level seems to suggest higher metabolic rate as well.