Just because you’re shedding the heat, doesn’t need you don’t need it. In fact, you needed to generate that heat so it could be shed. The human body works best at close to normal body temperature, and will break down if it gets very far from that temperature. Normal body temperature is usually warmer than the environment, so a human body in a comfortable environment will be shedding heat. If the body is to stay at the same temperature, it must produce more heat to replace that which is lost. If you drink icewater (in an environment cooler than the human body), then you’re shedding even more heat, which you must replace.
All that said, the amount of energy it takes to warm up that icewater is pretty small. Any calculations you see which make it look significant are forgetting about the difference between calories and Calories. Confusingly, there are two different units with almost the same name, with one Calorie (the unit food is usually measured in) being equal to 1000 calories (each calorie being the amount of energy needed to raise the temperature of 1 cc of water by 1 degree Celsius).
According to the logic of my post, “That heat was lost anyway” ONLY because the hot air is breathed OUTWARD onto the liquid nitrogen. However, if you allow the air to be motionless, or move towards you, so that you feel the cold, the you WILL use up extra calories to compensate.
By my calculations, then, one FoodCalorie is the amount of energy needed to raise the temperature of 1000 cc of water by 1 degree Celsius.
Phrased another way, one FoodCalorie is the amount of energy needed to raise the temperature of one liter of water by 1 degree Celsius.
If so, then it takes 37 FoodCalories to raise the temperature of one liter of ice water from 0 Celsius (freezing point) to 37 Celsius (body temperature).
That means Negative Twelve calories in a 12 oz. bottle of ice water. Not bad, in my view.
I missed the 5-minute limit on edits. Please adjust my previous post to read the following as its 3rd paragraph:
If so, then it takes 37 FoodCalories to raise the temperature of one liter of ice water (which is now entirely inside your body) from 0 Celsius (freezing point, its temperature when you drank it) to 37 Celsius (body temperature, its temperature when you finally urinate it out).
Yes, it’s shedding heat, so why would you need to burn extra calories to replace what is lost rather than just shed less heat? Princhester’s cite from the previous thread (well, I guess it was actually Truth Seeker’s cite, but I’m calling it Princhester’s from now on) indicates that if your core body temperature goes down a little, as it would from drinking ice water, your body simply constricts the blood vessels in the extremities so that it sheds less heat, thus raising the overall temperature back up without burning any extra fuel.
ETA: … up to a certain point, of course. Then your body once again starts actively generating heat. At least, that’s what it appears from the cite.
The element missing from your analysis, and the reason your link to a thread on home heating is inapt, is that they lack consideration of the body’s ability to regulate heat loss. Your home loses heat at the rate it loses heat, which varies only with temperature. The insulation surrounding the warm parts inside does not vary. Your body can lose a little, or lose a lot, depending on the extent to which it withdraws blood flow to the surface.
Your body can either put out 120 watts, or it can reduce heat loss by 20 watts.
Sheesh, Keeve, did you read my first post in this thread? Your understanding is wrong. Read my cite, fer cryin’ out loud. I don’t know what it is about the truthiness of this particular factoid that causes people to glom unerringly to it long after cites have been provided that show it to be wrong.
If you are referring to the one you linked to in Post #10 with the words “Read this very detailed paper on the subject”, then my answer is: I did try to read it, but as you pointed out, it is “very detailed”. As far as I can tell, it supports MY views.
For example, that source says: Intake of 250 g of ice releases an abrupt fall in the nasal temperature in a warm person, whereas the change in rectal temperature is smaller and delayed (Fig. 21-2). The cranial core temperature is more dynamic than the rectal.
Looking at that “Fig. 21-2” confirms two of my intuitive feelings: (1) that eating the ice does cause the temperature to go down, and (2) after some time the temperature dose come back up. Please tell me: From where does the body get the energy to bring the temperature back up, if not by burning calories?
(I confess to being less educated that you in these areas. If you could point out which part of that article you’re referring to, and a simpler-English version of it, that would be helpful.)
Same rebuttal as for Squink. You’re not considering the body’s ability to (in effect) vary insulation. Sure, your body must shed heat if it is warmer than the environment. But if it can drop the rate it does so by (in effect) increasing insulation (by withdrawing core temp blood from the surface) then heat you were generating and losing before can go into warming the water without using additional calories.
Some of the basic unsupported assumptions that appear in this debate are (a) that the body maintains standard temperature throughout every part of your body (b) that the body’s average temperature remains perfectly constant (c) that there is no hysteresis in your body’s “thermostat” such that anything that affects temperature inputs results in an immediate body response.
These assumptions are then applied to suggest that a cold input must perforce result in a calorie consumption increase.
I have seen no cites to support any of these assumptions.
I believe the idea is that it raises the overall temperature by reducing heat lost to the environment, specifically by constricting the blood vessels in the extremities, which would be like increasing the insulation of a house; with more of the metabolically-generated heat being kept inside, the body wouldn’t have to burn additional fuel to raise its temperature.
I expect Princhester or somebody else will correct me if my understanding is wrong at any point.
ETA: It appears I got the idea more or less right, from what Princhester posted while I was working on this response.
I have no idea why you believe that this supports your views. You’ll need to explain more. The comment you’ve quoted seems to show that at least locally, body temperature can drop. We are not debating that as far as I’m aware.
Bear in mind that I am not disputing for a moment that introduction of ice water into the body has to reduce temperature, and that calories have to be burned to increase the temp again. The question is whether introduction of ice water is effective as a diet technique: in other words, do you burn more calories than you otherwise would have by drinking the ice water.
The really key comment in the quoted article is this:
That is simple enough for me to understand. I’ll accept your word for it that the article said that, but it was in language too technical for me to understand.
Now, for the next logical piece to this puzzle: Does this process (the body increasing its insulation) occur even when someone drinks relatively small (<=1 liter) amounts of ice water, or does it only occur in more extreme situations, such as when the whole body is immersed in a large container of cold water?
(Going to bed now. No more posts for at least 9-10 hours. good night and thanks for your patience with dummies such as myself)
As I’ve said a couple times, as far as the cites I’ve found are concerned vasoconstriction is the very first standard step your body takes in reaction to a temperature drop under normal conditions.
Incidentally, while searching Google for information on nonshivering thermogenesis, I came across this page in a book, specifically page 220 in Exercise and Circulation in Health and Disease. It seems to discuss something vaguely similar to what we’re talking about here. Unfortunately, the page before this one isn’t included in the searchability, so I can’t see what the book was discussing here, but it does mention thermogenesis during cold stress and was kind of interesting to read.
My house loses heat faster when I leave my doors open in winter, and vasoconstriction takes energy to accomplish. In other words, it uses calories and generates heat.
Before swallowing a chunk of ice, your body is at a steady state with respect to heat loss to the environment. It’s at 37°C. Your metabolism is burning along merrily at 100 watts or so: some constant rate. After you swallow that chunk of ice, you experience a sudden cooling sensation, which your body makes up for by burning more fuel in an attempt to return to homeostasis: 37°C. Whether that fuel is burned to constrict blood vessels, or in a futile cycle of ATP synthesis and breakdown through the Na/K ATPase makes no difference at all, your body responds in a way that increases the rate at which calories are used.
When eating ice, you also have to include water’s heat of fusion, the energy you need to put in to melt ice. That’s 79.4 calories per gram, or 79.4 food calories (also called Calories or kcal) per liter. So the total heat needed is 116.4 Calories per liter.
To borrow some rhetoric used by Una in the thread you linked to, your next post is going to include cites for the following propositions:
vasoconstriction takes significant energy to accomplish.
your body burns more fuel in an attempt to return to homeostasis if you swallow a chunk of ice/your body responds in a way that increases the rate at which calories are used.
Put up or shut up. I’ve provided cites that say the latter is wrong except when your shell temperature is already low. Stop asserting and start meeting GQ standards.
I’m curious about what sort of non-shivering thermogenesis occurs in adults.
The Wikipedia article on thermogenesis says “Non-shivering thermogenesis usually occurs in brown adipose tissue (brown fat) that is present in human infants and hibernating mammals.” But as we’ve already seen, adults have virtually no brown adipose tissue.
Clearly there’s heat generated in every cell as it metabolizes food – 60% of the energy in food gets turned into heat rather than ATP, as we’ve discussed. And the body has the shivering mechanism to burn extra fuel and warm you up when the normal heat production and the insulating methods used to keep it in are inadequate.
Is there any other mechanism the body employes to generate heat in an adult?
Yes. Unfortunately it’s not known exactly what it is. One of the major contenders is a futile cycle of ATP synthesis and breakdown through the Na/K ATPase, but that idea’s been floating around for 20+ years, without proof. Turns out it’s hard to maintain thermogenesis in cell cultures, and hard to measure flux through the pathways in intact organisms.
Thanks for that link. I see that the last post in the thread quotes a site that makes the type of argument as Princhester’s (but to deny that exercising in cold weather necessarily burns more calories, rather than drinking ice water).