Since calories are a measure of energy, and heat is energy, does one intake more calories with food that is temperature hot as opposed to eating that same meal at a lower temperature.
I thought “Joules” were a measure of calories.
Well, sort of, but not in the way you imagine. Your body obtains energy through digestion of food through chemical reactions, and it does not obtain any more chemical energy from hot food than cold. However, your body is constantly expending energy to maintain your body temperature, and when you eat cold food, you do burn slightly more energy in order to maintain the same temperature. Similarly, eating hot food heats you up.
As a simple example, let’s say you ate 1 pound of frozen turkey. I will just assume that the heat capacity of this is equivalent to 1 pound of water, which is close enough. The heat capacity of water is about 4 Joules per gram per degree Kelvin. 1 pound of water is about 450 grams. Body temperature is about 100 F (310K), frozen meat 32 F (270 K).
So: 4 Joules * 450 grams * (40K) = 72 kJ = 17 kcal
So, eating 1 pound of frozen turkey instead of turkey at body temperature causes you to burn an extra 17 calories.
Conversely, eating 1 pound of just-cooked turkey at around 160F causes you to burn about 17 less calories, since it provides heat you would otherwise have to produce yourself.
This is a very half-assed calculation, and I’m currently coming down with the flu or something, so take it at your own risk. The actual effect on you will vary depending on whether you are in a hot environment or cold environment to begin with.
Joules and calories are both measures of energy. Food is actually measured in kilocalories (kcal).
To put this into perspective, 4 ounces of turkey has 153 calories, for 612 calories per pound, so you’d save only 2.78% by eating frozen turkey over body temperature turkey (or 5.56% vs cooked turkey). Of course, some foods like celery will actually cause you to loose more calories (and yes, it actually does have “negative” calories, not accounting for temperature). There’s even a diet going around based on drinking ice-cold water to lose weight based on this ides (water of course having no calories, but celery and other net-negative calorie foods (lettuce has even fewer calories per gram) would work better, with the added plus of filling you up if you eat enough)
Note that there are two usages of the word “Calorie” which refer to the same thing but in different quantities:
By convention, the food calorie is usually capitalized (as in the symbols given), although it often isn’t when written out (as in the posts here).
And, as I understand it, people usually radiate some surplus body heat from calories that they burn for other reasons, so if some of that heat goes to warm up cold food instead, it doesn’t really burn any extra calories.
Nitpick: if the turkey is truly frozen, then you would also need to consider the heat of fusion - the energy required to convert frozen turkey at 32 degrees to thawed turkey at 32 degrees. This energy is substantial, however few people actually eat frozen turkey; it’s far more likely that they’ll be eating refrigerated/unfrozen turkey that’s somewhere between 32 and 40 degrees F.
As for the effects on calorie usage by the body, your example assumes that the eater of the turkey is struggling to keep warm. If the two examples (serving cold or hot turkey) are carried out in an environment where the eater is struggling to keep cool, then eating hot turkey doesn’t reduce the eater’s heating burden - it just makes him sweat more.
(and of course, we’re assume frozen cooked turkey. Raw turkey, cold or warm, will definitely provide fewer calories than cooked. There’s a reason the (proto)human species really took off once they started cooking.)
Oh god, I can’t help myself. “Fewer,” not “less.” “Were,” not “was.”
I’m so sorry.
–Cliffy
Arbitrary prescriptivist nonsense. Language Log » Stupid less/fewer automatism at the WSJ
Another great username/post combo!
One of Cecil’s few columns which is wrong, since he makes the mistake of ignoring the issue that chrisk raises above.
Actually, unless you are somewhere cold and are entirely inactive, there are few circumstances when your body burns extra calories just to supply heat. Heat is a byproduct of normal body functioning, and mostly your body throws it away. Heating cold beer or turkey will under most circumstances just cause your body to discard less heat - if that - not burn more calories.
:smack:
"Eating cold beer or turkey will under most circumstances just cause your body to discard less heat - if that - not burn more calories. "
and here I was hoping my midnite fridge raids could count as a diet plan… damn, foiled again!
(Bolding mine.)
It sounds like you’re considering 1 lb of frozen turkey melting in our mouths instantly or ingested by rapid successive sliders of frozen turkey hockey pucks (mmmm, frozen turkey hockey pucks…).
Energy expended on breaking up the ice to swallow must be figured in. Our maximum jaw force–as a one-shot, I believe, not repeatedly, and determined unilaterally, is approximately 500, 700, and 1000 Newtons for the canine, premolar, and molar, respectively (See [cite]). A fascinating article on morphology of hominids and functions of craniomandibulator system relative to group and diet, among other things.) i dont know the metabolic expenditure of exerting the force.