Talk:Calorie

Contradictory first paragraph

I am trying to understand what a calorie is but this contradiction makes definition unclear. Can someone who knows please fix this!? First: A calorie is a unit of measurement for energy. Then: The word "Calorie" is often mis-used to mean "energy" Thanks! user:rusl

There is no contradiction here: "fat" is the name of a unit of measurement (a reference measure), while "energy" is the name of a quantity (something that can be measured). Some people fail to see the conceptual difference between quantities and units and misuse the names of units (such as "calories") to denote quantities. They say "this snack contains a lot of calories" instead of "this snack contains a lot of energy". (The lack of distinction between unit and quantity is particularly pronounced in American English, where a common remedy seems to be to add the suffix "-age" to a unit name to turn it into a quantity, e.g. "amperage" and "footage" for quantities such as current and length.) Markus Kuhn 12:47, 22 March 2007 (UTC)

While the units of measurement are different from quantities, I still believe both of the above mentioned sentences are basically correct. Even if they are not, I don't see how it is a significant enough issue to warrant inclusion in the article, let alone the first paragraph. If anywhere, perhaps it should be in units of measurement. Benna 02:47, 29 March 2007 (UTC)

I struck the last sentence of the first paragraph, as it was beyond confusing. I think it would be a good idea to spread this understanding of units versus what the units measure, and "Calorie" is a good example of that, but not in the introduction to this specific unit. This confusion only seems to happen with the word "high-calorie", not the word "calorie". One would never say something is tall by saying it's "high-feet", so I think this should be part of the "Calorie" page, but definitely not in the intro. 76.167.124.179 21:56, 15 May 2007 (UTC)

Elevation: At what elevation does this definition of a calorie apply? We know that the energy required to heat water is greater at higher elevations, but I don't see/know anything about if there is a standard in this definition. If there is not, it seems like the definition in fact defines very poorly. — Preceding unsigned comment added by TooManyTooMuch (talk • contribs) 21:39, 21 January 2011 (UTC)

The definition specifies that standard atmospheric pressure is to be used; pressure is what typically varies with elevation, leading to the variations you're thinking of. So you can think of the definition as using sea level as elevation; but the elevation isn't really what matters – what matters is the ambient pressure. Eddy. 84.215.6.188 (talk) 12:00, 11 July 2011 (UTC)

Scope

Please keep the calorie article focused on the unit of measurement for energy of that name, with a few notes on its particular use in food-labeling regulations. More detailed discussions of all other issues related to human nutrition, diet, weight control, etc. really belong into articles of their own. In particular, please do not spam the article with countless URLs to the many advertisement-financed web food/exercise-calories tables out there. Markus Kuhn 17:15, 14 June 2006 (UTC)

Web-based calorie sites

Agree with Markus that this category should not be spammed with food calorie table URLs. But to the extent that they are here, marketing claims relating to the numbers of foods should be required to be more detailed and accurate. Most data falls into the following categories:

• Basic foods (usually from the USDA list)
• Restaurant foods
• Packaged foods, from the Nutrition Facts labels
• Composite data, usually computed for recipes

Specifying separate figures for each category makes it easier to evaluate the quality of each web site's data. for TheDailyPlate, in particular, is really suspect and amounts to a marketing claim by the proprietors of the site. It seems to mostly be data of type #4, mostly from RecipeZaar, which is of dubious use to most people. It also tends to be inaccurate, since RecipeZaar automatically computes calorie counts from ingredients using USDA-derived data, and simply omits ingredients that it cannot match. As a minor side feature of a recipe site, the calorie counts have not been given much attention or priority by RecipeZaar.

Perhaps a format like this would be good:

• Mr. Calorie. Claims 45,000 calorie data as follows: USDA basic foods; 5,000 items from 50 chains updated quarterly; 10,000 items from 100 chains screen-scraped from competing web sites and not updated (includes duplicates); 13,000 packaged foods, 2,000 entered by our staff, 11,000 screen-scraped from other web sites; 10,000 recipe calories from RecipeZaar

so how do they calculate "calories burned" when exercising? Seems like there was some equation linking energy with "work" but I don't recall... Anyone know?

Question: Calories Burned? is there an equation somewhere?

so how do they calculate "calories burned" when exercising? Seems like there was some equation linking energy with "work" but I don't recall... Anyone know?

energy = work Markus Kuhn 10:25, 11 April 2007 (UTC)

Thank you Markus ;^>

However, for the sake of the original questioner, who might not be able to fill in the details: consider someone with a body-mass of about 100 kg (220 lb); on Earth's surface, gravity pulls at just short of 10 N/kg, so they weigh nearly 1000 N or one kN (kilo-Newton); suppose such a person climbs stairs to a floor that's a little over 4.2 metres (e.g. 14 ft, so up about two floors in a somewhat compact building) above where they started; they'll have done (multiplying weight by height) about 4.2 kN.m = 4.2 kJ, i.e. 4200 Joules, of work; dividing by approximately 4.2 Joules / calorie this gives about 1000 (short) calories or one long Calorie. So a 100 kg person climbing two floors of a compact building "burns" about one long Calorie; that's about a quarter of the energy content of a gram of sugar, so they'd need to climb about eight stories (c. 17 metres, c. 55 ft upwards) to burn off the calories in a gram of sugar; to burn off the energy content of one ounce (a bit over 28 g) of sugar you'd need to climb nearly half a kilometre (1560 ft).

So, for calories burned by climbing vertically, the formula is weight × height; this gives the energy expended. As ever for a quantity where several units are available, you divide the answer by the unit you want it in (4.2ish J for the short calorie, 4200ish J for the long Calorie used in food labelling).

Of course, if you know your body-mass in pounds and the height in feet and want to measure the energy in long Calories, you're going to need a factor of (pound-weight)×foot/Calorie = 9.81 N/kg × kg/2.2 × 0.3048 m / (4200ish J), which is about 0.000324 or 1/3087; so (body-mass in lb)×(height climbed in ft)/3087 = (energy burned in Calories).

More generally, the energy you burn depends on what work you're doing; usually it's not as simple as lifting yourself through a vertical height, but that should serve as a reasonable rough guide with which to model other activities. If you lift weights, multiply the height you lift the weight through by its weight and the number of times you lift it. If you run, a crude model would say your body moves up and down, in each stride, by a moderate fraction of a metre, say 0.4m; multiply that height by your weight as above and the number of strides you ran (which, in turn, you can estimate by the distance you ran divided by the length of your typical running stride; which is likely a metre or two). Other forms of exercise may be harder to estimate – I'm afraid you'll have to do your own home-work on that !

Then you might also want to take into account the efficiency of the human body; when I climb stairs, I get hot as well as gaining altitude, so I'm actually expending more energy than the above takes into account; and when we digest food, we don't get all of the energy content out of it (partly because we expend energy in extracting the energy content from it); but maybe food-packaging calorie-counts take the latter into account (I've no idea). Eddy 84.215.6.188 (talk) 13:11, 11 July 2011 (UTC)

Question: Calories

Why is the fat measured by the weight of animal that consumes, as opposed to the SI unit for water which is volume??

1kg water equals 1 liter water, so it doesn't really matter

In any case, the calorie isn't an SI unit. If you want to comply with SI standards, you have to use the Joule instead, and the only reason most people don't is because consumers have gotten so used to using calories, the same way they're used to pounds and miles.

Actually 1 kg water is just approx. 1 liter. Also it would be nice to have an exact value onhow many Joule a Calorie is.

1. 1. 1. It is difficult to say how many joules a calorie is. A 15° calorie is 4.1858 joules, and the international steam table (IT) calorie (4.1868 joules). There are also other types of calorie. In bomb calorimetry which is used to calculate enthalpies of chemicals (and foods ie. their calorific content, a calorie is defined as the amount of heat liberated on combustion of 1g of pure benzoic acid.)NB- water can also be used in bomb calorimetry of food83.245.22.39 17:02, 3 January 2007 (UTC)AB83.245.22.39 15:10, 3 January 2007 (UTC) ####

The calorie is measured by the mass of the water it heats because water's density depends on its temperature. If you were defining the calorie by the volume of the water, you would have to choose whether to use the starting volume of the water or the end volume (after it's been heated by 1 °C).

You have to do so anyway since specific heat is temperature dependent also. JIMp _talk·cont 20:57, 15 July 2010 (UTC)

If you warm a given mass of water, its mass is still the same at the end (give or take relativistic corrections O(10⁻¹³), which are dwarfed by the O(10⁻⁴) experimental errors in measurements anyway) but its volume shall have changed. So if you measure the energy it takes to warm a body of water from one temperature to another, dividing that energy by the mass of the water doesn't depend on whether you measured the mass before or after warming; whereas dividing the energy by the volume of the water does depend on whether you use the water's volume before warming or after warming, since these two are different. (Of course, you next also divide by the temperature difference, but that's not at issue here.)

The reason why one has to specify the temperature range over which one is defining one's calorie is that the heat capacity of water does in fact vary with temperature; it's a little over 4.2 J/g/K for short temperature intervals about 4C and appreciably less, below 4.19 J/g/K for temperature intervals near 15C. It remains that (at a given pressure, usually atmospheric) the amount of energy needed to warm a body of water from one temperature to another is proportional to its mass and the ratio of energy/mass doesn't depend on whether you measure the mass before or after (as long as no appreciable amount of evaporation is happening). Eddy. 84.215.6.188 (talk) 13:31, 11 July 2011 (UTC)

Kcal

How is it that a kcal is equivalent to 1 cal when it is also listed as 1000 cal.

I think there is a mistake in citing the number of calories in a pound of body fat. It should be 3500 kcal and 3500 calories.

This helped me! It comes from Spanish Wiki...

1 kcal = 1 Cal = 1000 cal = 4,184 kJ = 4.184 J--Arcillaroja (talk) 17:12, 2 November 2008 (UTC)

Grams and kilograms

I've restored the units to the definition of a calorie (little c), because (a) that's what the international definition is, and (b) 1 mL of water is 1 g only at specific temperatures (technically only one temperature value). -- MarcoTolo 20:47, 5 March 2007 (UTC)

Mature article

I believe this article has reached a high level of maturity and there is little further to improve. The vast majority of edits that we see make it worse and seem to be done by people who do not even bother to read the full article, the references or the talks page. In fact, I now find it regularly necessary to undo about month worth of edits just to keep it in good shape. I think it would be a good idea to give the article some more protected status at this point. Markus Kuhn 10:32, 11 April 2007 (UTC)

Calories and weight gain

The introductory paragraph of this article contained a comment to the effect that a given number of calories could be expected to produce a certain weight gain in the average person. Given that this makes no reference to exercise, or to the food type whereby that energy is consumed (fat is more likely to be stored and result in weight gain than is carbohydrate, in moderate quantities), and given that the comment was dramatically out of keeping with the subject matter of the rest of the paragraph (discussed energy, units, the use as a measure of food energy, and then suddenly a comment on weight gain), I decided that the comment was both spurious and stylistically incongruous, and deleted it. I really don't think it belongs there. cmsg —The preceding unsigned comment was added by 86.31.109.93 (talk) 01:22, 23 April 2007 (UTC).

I also agree with the statement that there's no cause to highlight in the first paragraph the distinction between a quantity, and a unit thereof.

Counter Opinion Regarding Calories and Weight Gain

BUT isn't there recent research calling into question this traditional conclusion that fat is more likely to be stored than carbs? Isn't there research calling into question the correctness of traditional calorie counts of food, because the original research methodology for measuring these calories is not equivalent to the biological processes within the human body? Shouldn't there be reference to these controversies in the article?

Meh. Probably makes more sense to have a generic mention, in the opening, of the fact that nutritionists make a big deal of energy content, expressed in long Calories, and link to some general discussion of nutrition. Put the controversy there, where it belongs, rather than on a page that defines the archaic unit (which contains enough complications as it is, what with the glorious absurdity of "calorie" also serving as a synonym for kilo-calorie, compounded by the diverse choice of temperature ranges over which to measure the heat capacity). Eddy. 84.215.6.188 (talk) 13:39, 11 July 2011 (UTC)

I agree. There's a note at the top directing readers to the article Food energy which is the appropriate place to talk about ... food energy. This article is about the unit ... or units. JIMp _talk·cont 14:51, 11 July 2011 (UTC)

Terminology

1 cal_INT = 4.1868 J (1 J = 0.23885 calIT) 1 cal_th = 4.184 J (1 J = 0.23901 calth) 1 cal₁₅ = 4.18580 J (1 J = 0.23890 cal15)

Can someone explain what the subscripts mean?

Without actually knowing the answer, I'd be willing to guess that INT is an INTernational calorie, th is a thermochemical calorie, and 15 is a 15°C calorie. These are described in this section. --86.148.122.55 19:45, 13 August 2007 (UTC).

Need More Background on The ThermoChemical Calorie.~

The International Table Calorie is now defined as 4.1868 Joules in accordance with the determination of the fifth International Conference on Properties of Steam (London, July 1956). This detaches the calorie from the properties of water and yet retains a value very close to the properties of water.

The ThermoChemical calorie is defined exactly in terms of Joules as well but uses 4.184 Joules. Who gave this definition and what was the reason? What does "ThermoChemical" imply?

Calories and weight loss

1 pound is equivalent to approximately .45 kgs, so the weekly kcal deficit or surplus to lose/gain one kg should be less than that required to lose one pound.

According to the paged sourced, http://www.nlm.nih.gov/medlineplus/ency/article/001940.htm , the weekly deficit/surplus required to lose/gain one kg/week is around 1600 kcal. (0.45359237 x 3500 kcal). That translates to a reduction of 500 kcal/day to lose one pound a week, and approximately 230 kcal/day to lose one kg.

A reduction in calorie intake by 7800 kcal/week, a reduction of more than 1000 kcal/day, is potentially dangerous. Maybe it should also be specified that the numbers stated are per week and not day, since they could get mixed up. —Preceding unsigned comment added by 213.113.219.51 (talk) 21:37, 6 December 2007 (UTC)

Are these all kcal or cal? —Preceding unsigned comment added by 122.167.218.224 (talk) 12:00, 6 January 2008 (UTC)

Counter comment on discussion above I think this comment is total hooey. If you reduce your calorie intake by 500 calories below a maintenance level, you turn off your metabolism, which makes weight loss more difficult. Moreover calories, i.e. the amount of heat produced when foods are tested in oxidation reactions in a laboratory, have little or nothing to do with how food is metabolized in the body.

What kind of Calories are on nutrition labels?

According to this article there are many kinds. But, which ones are used to measure food energy(at least for U.S. food companies). 207.177.111.36 (talk) 15:01, 7 December 2007 (UTC)

Go back in the article's history about a year, and you'll find it all explained in great detail. This article has recently been edited to death and needs resetting to an older state. Markus Kuhn (talk) 10:44, 6 March 2008 (UTC)

Numbers need citation

I looked all over the internets and couldn't find clear sources for kcal/grams of fat, protein or carbohydrates. Some books that I've read say that carbohydrates are actually 3.75kcal/g. Needs clarification and citation. Thanks--70.74.82.114 (talk) 22:58, 5 January 2008 (UTC)

Check out food energy for the information you are looking for. Markus Kuhn (talk) 17:52, 30 March 2008 (UTC)

Confusion between kilocalorie and Calorie

Most people coming to this article will be looking for the definition of Calorie (that's large Calorie, the one used to measure food energy content), which is a kilocalorie. This article does not make the distinction very clear. That's because it's a mish-mash of rubbish written by obsessive nerds with no mind for the target audience of, or proper scope for an encyclopaedic article. Ah well, I suppose that this is Wikipedia.

Wikipedia (n): A mish-mash of rubbish written by obsessive nerds with no mind for the target audience of, or proper scope for an encyclopaedic article. —Preceding unsigned comment added by 121.45.143.14 (talk) 11:31, 16 March 2008 (UTC)

The confusion is in the real world; not in Wikipedia. It is easily avoided—just stick to joules. Gene Nygaard (talk) 03:25, 31 March 2008 (UTC)

Hear! Hear! Jɪmp 03:28, 31 March 2008 (UTC)

Wait a minute; let me rephrase that.

There is no real confusion, either in the real world or on Wikipedia, for a couple of reasons:

• There are only 27 or 28 surviving dinosaurs anywhere in the whole world who ever still use calories to measure anything in sciences such as chemistry and physics. Nobody uses them any more, the rare confusion might come in something more than 60 years old. The only calories in use today are the ones in the medical sciences and everyday use, the food calories. The small calorie is essentially dead.
• Nobody ever uses prefixes with the large calorie. So if you see "kilocalories" you know that this is somebody who wants to appease the old users of the small calories, not realizing that such users don't exist any more.

So if in the context of modern usage, you hear somebody say "calories" (or even if you have really good ears and hear them say "Calories"), or if you hear them say "kilocalories", they are all the same thing. Doesn't matter in the least which term you use. There is no real confusion, just an imaginary one by people oblivious to the world around them. Gene Nygaard (talk) 03:41, 31 March 2008 (UTC)

They use the term kilocalorie in Japan. Jɪmp 03:50, 31 March 2008 (UTC)

Food marketing industry of course tries to establish the "large calorie" as a valid or even just practical or necessary unit. So there is plenty of motivation and money behind creating a completely un necessary unit that does not make any sense except to confuse consumers. If the large calorie symbol "Cal" becomes "established" we may soon see e.g. travel agencies inform you about e.g. the distance from the hotel to the beach in large meters "M". So be prepared to walk 10km (10 000m) instead of the 10m you may have been hoping for. I may also prefer to refer my body weight or the one of my child in "large gramms". I can see weight conscious people claim to weigh 100G rather than 100kg who could hear the difference. Apart from the fact that it is completely unnecessary it only works in writing - it can only be seen as a joke or bold marketing stunt by a greedy industry that tries to sell us high energy food.

So in case a peanut butter producer adds the funny unit again into this article I post my modification here so that people can re-correct it if they like... let's hope that we consumers win this battle and not the PR departments of high energy yummy foods :) - alternatively we could - just for fun - start introduce "large" meters or grams on the other unit definition pages - this would be fun or at least a great joke and some industries will love it!

So here is my suggested and saved version for those interested in providing serious information:

One calorie (symbol: cal) is the amount of heat (energy) needed to increase the temperature of one gram of water by 1 °C. 1 cal is about 4184 J. "J" is the symbol for the official unit for energy, the "Joule". 1 kcal = 1000cal hence 1kcal is 4184 kJ. "k" is the official pre fix for units meaning "kilo" or a 1000 units of something e.g. 1kg = 1000g.

[Note, in recent decades the unit "calorie" has been "modified" (presumably for marketing purposes in the food industry) to conceal high energy content in food and confuse customers - especially in developed countries with high numbers of overweight people.]

Sometimes, on food labels, you may find "calorie" spelled with a large "C" e.g. "Calorie" or "Cal" to hide the fact that it contains actually 1000 calories - not just "one" calorie. The "inventors" of this unit gave it the name "large calorie" sometimes also referred to as "kilogram calorie". As this "unit" only works in writing - and is completely unnecessary - it makes no sense to use it other than confuse consumers.

The "calorie" - as opposed to the official energy unit "Joule" - is commonly used to express food energy, e.g. when discussing dieting or nutrition plans or simply reading the energy content on food labels. This is probably because 2500 kcal is smaller than 10000 kJ, the recommended energy intake for an adult person per day. —Preceding unsigned comment added by 220.245.124.221 (talk) 17:58, 23 October 2008 (UTC)

Heat

Revision as of 21:51, 27 February 2008 by User:Unfree was anything but "Minor rewording". Amongst other things,

A calorie is a unit of measurement for energy.

was changed to

The calorie is a unit heat, a form of energy.

This is a major change. The unit now only applies to energy in the form of heat. Has the unit been dropped from nutritional labels recently? Food energy is certainly not a form of heat. I'll be reverting this substantial change. Jɪmp 07:36, 30 March 2008 (UTC)

ISO 31-4 (Annex B, informative, referenced) describes the calorie as a unit for the quantity "heat" or "quantity of heat". Recall that food energy was historically defined by using a bomb calorimeter that measured the amount of heat given off when you burn the food in a high-pressure oxygen atmosphere. The definition of the calorie is certainly a measurement of heat. All these suggest that describing the calorie as a unit of heat is perfectly correct. I'm therefore reverting your reversion. Markus Kuhn (talk) 10:18, 30 March 2008 (UTC)

Here's a web reference about the SI systems and calories under "Other unacceptable units": http://physics.nist.gov/Pubs/SP811/sec05.html#5.1.4 that could be useful in a few places relating to the SI. Calories in food are potential or eventual calories - we "burn" calories in our muscles etc... Ephdot (talk) 11:55, 30 March 2008 (UTC)

It might have been measured by means of conversion into heat but food energy is a form of chemical energy not heat. We may colloquially use the word burn but muscles are not heat engines, they produce heat but as a by-produce, they don't convert that heat to work. If ISO 31-4 describes the calorie as a unit of heat, they ignor common practice ... or common practice ignors ISO 31-4. Jɪmp 00:49, 31 March 2008 (UTC)

The calorie has a lot of historic baggage, so this article will have to address that. As I understand it, the difference between a unit of heat and a unit of (mechanical) energy/work had mainly to do with managing measurement uncertainties. Historically, the thermal capacity of water was not known (or defined?) precisely enough to agree on a high-accuracy conversion factor between heat and mechanical forms of energy or work. Therefore, independent units were defined for both originally. In laboratory practice, the energy released in exothermic reactions (e.g., food energy) has been quantified in the form of heat, therefore historically using the unit of heat rather than the unit of mechanical work was the obvious choice. Chemists could calibrate their equipment and compare measurements without having to worry about what all this meant in terms of force·length. I'm not sure whether we would do a proper service to Wikipedia readers if we restricted our horizon to interpreting the current edition of the online version of the SI Brochure in a strictly dogmatic manner (the truth as laid down in the holy scripture by the last CGPM proceedings editor), and neglect any of the historic reasoning and motivation behind the unit, something Gene Nygaard seems to prefer. The calorie remains a unit of heat, and the fact that we have now agreed exact conventional conversion factors to the SI unit of energy doesn't change that historic truth. Markus Kuhn (talk) 21:57, 15 June 2008 (UTC)

Both current use and historical use should be thoroughly covered. The current version of the article doesn't do this. The first sentence, "The calorie is a pre-SI unit of energy, in particular heat.", in especially does not do justice to the facts. It's a unit of energy, in particular food energy, historically defined in terms of heat. JIMp _talk·cont 01:26, 16 June 2008 (UTC)

Weird notions about usage

Some people (most recently User:Markus Kuhn, but others in the past as well, such as 121.45.143.14 above) seem to have some weird notions, such as:

• Americans normally capitalize the initial "C" in food calories, or
  • more generally, that all people do.
• That people in the UK and some other places don't use the word "calories" for large calories, but instead use small calories and attach the prefix "kilo-" at the scale used in nutrition measurements.

That is a crock of nonsense.

• For the first point, take a look at Image:Nutritionfacts.png.
• For the second point, consider these Google results:

Google	hits
calories site:uk	320,000
kilocalories site:uk	2,390

How many of those 320,000 do you suppose refer to food calories? Gene Nygaard (talk) 04:02, 31 March 2008 (UTC)

Here's an interesting tidbit, even if it probably doesn't fall into he category of a reliable source:

Yahoo!Xtra Answers http://nz.answers.yahoo.com/question/index?qid=20080308001534AAw38Ok

Resolved Question

How many calories is 331 kcal?

* 3 weeks ago

Best Answer - Chosen by Voters

331 calories.

Kcal is the scientific term, calorie is the common term

* 3 weeks ago

Looks like it might have been the only answer, but I might word it a little differently while basically seconding it; the distinction between symbols and words is also a factor, just as in the case where many people continue to use microns, despite the CGPM having told us not to do so 40 years ago, but almost nobody uses the symbol µ for them any more—even the dinosaurs who hag onto the outlawed word now usually use the proper symbol µm with that word, rather than its former symbol. In other words, there can exist changes in usage of either the spelled out words or of the symbols, somewhat independent of each other. Gene Nygaard (talk) 13:34, 31 March 2008 (UTC)

Common usage is indeed a relevant part of the story. All the same, I just went and looked at a bag of sugar in my kitchen cupboard and it (in Swedish) lists the energy content per 100g as 400 kcal and as 1700 kJ. So perhaps the anglophone world does conflate the Calorie with the kcal, but don't assume the same is true for the rest of the world ! I will hazard a guess that the EU has issued a directive on food labelling that requires the use of kcal and forbids the use of Calorie; with the result that, in England, one must read "kcal" as "Calorie" (and naturally no-one can hear your capitalisation) to have your hearers understand you.

I think the most appropriate way for an encyclopædia article to deal with this is to state that the name is used for two units; to list the two units – with their "full" names, short calorie and long calorie, so that later text can refer back to them unambiguously – giving the definition of each; then to briefly explain the history and where it has left us – the short calorie was a scientific unit of measurement, now deprecated by SI; the long calorie entered the vernacular as a short-hand used in the context of nutritional energy and has survived; it is sometimes called Calorie, capitalised, in an attempt to limit confusion; and that, in practice, any use of "calorie" without a kilo-prefix means the long calorie while any use with the prefix means the short calorie, with the mildly perverse effect that dropping the kilo-prefix doesn't actually change how anyone is going to interpret it. Eddy 84.215.6.188 (talk) 14:25, 11 July 2011 (UTC)

Also, in defence of the "long" calorie, it does actually make more sense to use the kg as unit of mass, since that's the unit that's used in building up the Joule as kg.(m/s)²; an "energy per unit mass" is a squared velocity so its natural unit is the square of your system's unit of velocity. Not that this is of any but historical interest; the unit is archaic. Eddy 84.215.6.188 (talk) 15:26, 11 July 2011 (UTC)

"in particular, heat"

The change to that wording is a slight improvement, Markus Kuhn. But still slightly off. In comparison, note that Resolution 3 of the 9th CGPM (1948) says "The unit of quantity of heat is the joule."

Yet, I doubt seriously that you would claim that this limits the joule to only measure that kind of energy and not any other kind of energy and not the quantity called work (physics). So why are you being so foolish with respect to the calorie? Gene Nygaard (talk) 13:17, 31 March 2008 (UTC)

"... in particular, food energy ..." if anything (and, no, I don't buy the you-burn-the-food-to-measure-the-energy argument). Maybe historically a measure of heat but not today. JIMp _talk·cont 11:33, 27 January 2009 (UTC)

I don't think it's really faithful to describe it as a unit of heat; it's really a unit of chemical energy, measured by exploiting the early-established equivalence of chemical and thermal energy (later recognised as equivalent to mechanical work). So it's expressed in terms of the extent to which water is heated by a chemical reaction, i.e. by a measure of heat, but it always was primarily a way to thereby measure the amounts of chemical energy.

How about:

The calorie is a unit of energy now primarily used for the chemical energy content of food. It was previously used for chemical energy generally, as determined by the extent to which the energy liberated by a reaction would heat a body of water; however, in scientific use, the Joule is now favoured.

Then deal with its brief history, the dichotomy between short and long forms, etc. Eddy 84.215.6.188 (talk) 14:25, 11 July 2011 (UTC)

Calories and the Metric System. Countries and use....

It's interesting that although the Calorie is based on the Metric system and designed to fit in with it, it now seems to be officially rejected by the Metric authorities...

Since it's based on the gram and the Celsius degree, it's a perfect match for the Metric system - just as a mililitre is the same as a cubic centimeter and for water weighs one gram. And a litre of water weighs one kilogram. Whereas the joule has no such direct connection.

Not really; the crucial detail you're missing is that SI is based on the direct combination of its base units. That the ml is the cm³ is indeed a consequence of relevant definitions; the litre is defined as one thousandth of a cubic metre (equivalently, as a decimetre cubed; but almost no-one ever mentions the decimetre except in this formula and many are familiar with decilitres, as they're a practical unit in many contexts, and decimetre sounds too similar to it, with the lamentable result that I've heard (probably more often than the correct form) the litre's definition given as "a decilitre cubed", from which one may infer that litre is a pure number, the square root of 1000 – but I digress) so the millilitre is indeed the cube of the centimetre. In contrast, a litre of water merely happens to weigh approximately one kilogram; it's undoubtedly not a coincidence (someone surely chose one of the units to make this approximately right) but it's not the definition (contrast the UK gallon (or Queen Anne beer gallon; the US uses a Queen Anne wine gallon of 231 cubic inches) which was defined as the volume of 10 lb of water under specific conditions). Given the units of mass, length and time, one arrives at a natural unit of energy, Joule = kg.m.m/s/s. One could have then chosen, as unit of temperature, the change in temperature that one Joule produces in one gramme of water; however, instead, they chose one hundredth of the temperature difference between the boiling and freezing points of water; since these choices give different answers (the latter is about 4.2 times the former), the specific heat capacity of water is about 4.2 J/g/K rather than about 1. SI doesn't officially care about making water's properties have tidy values – and, in general, you can't do it for all of them, anyway – so it's not enough that the calorie is based on gram and Kelvin: it's also based on the specific heat capacity of water, which isn't a defined unit of SI. So SI prefers the unit of energy that's based on the kg, metre and second. Eddy 84.215.6.188 (talk) 15:09, 11 July 2011 (UTC)

It would be interesting to see a list of which countries use KJs vs. Cals in food labeling. I know that in the States and Canada Cals are used exclusively and that in Europe the Calorie is still the unit used, though KJs are sometimes given as well. But in Australia and New Zealand, the KJ has apparently become the primary unit for measuring food energy, though Cals are often listed as well.

Does anyone have information for other countries?... —Preceding unsigned comment added by 67.54.230.17 (talk) 03:55, 15 June 2008 (UTC)

That would be an interesting list. No, the joule has no such connexion. It's got a much more direct one:

1 J = 1 kg·m²·s⁻²

thus fits in a whole lot better than a unit whose definition depends on how warm you want your gram ... or kilogram ... of water. JIMp _talk·cont 09:13, 21 June 2008 (UTC)

Though SI units are prevalent in Denmark, energy in food is always listed as both kcal and kJ. Teglsbo (talk) 12:17, 17 August 2008 (UTC)

... as required by legislation (see references in food energy article) in all EU countries. Markus Kuhn (talk) 12:57, 17 August 2008 (UTC)

SI is also used in Australia. JIMp _talk·cont 11:29, 27 January 2009 (UTC)

Deprecation

The following was removed by an anon.

Since the many different definitions are a source of confusion and error, all calories are now deprecated in favour of the SI unit for energy, the joule.

But aren't they depreciated? If so, by whom? Can we not source & clarify this? JIMp _talk·cont 16:32, 27 February 2009 (UTC)

s/depreciated/deprecated/ ! (section title fixed) A thing depreciates as its value goes down; one deprecates a thing when one has decided to discourage folk from using it. Eddy 84.215.6.188 (talk) 15:33, 11 July 2011 (UTC)

Color

What is the purpose of the funny coloring of the conversion factors in "Variations"? --A. di M. (talk) 15:14, 2 March 2009 (UTC)

Less confusing now (i.e., big C vs small c). —Preceding unsigned comment added by Port Tiger (talk • contribs) 20:52, 17 July 2009 (UTC)

Calorie vs calorie

"The kilogram calorie, large calorie, food calorie, Calorie (capital C) or just calorie (lowercase c) is the amount of energy required to raise the temperature of one kilogram of water by one degree Celsius."

This is wrong, Calorie with a capital C is different from calorie with a lowercase c. —Preceding unsigned comment added by 72.130.55.225 (talk) 18:34, 20 July 2009 (UTC)

This is a distinction that is not followed by everyone (no surprise since it amounts to inventing your own capitalisation rules and doesn't work if the word would be capitalised anyway, e.g. at the beginning of a sentence) and thus the article is correct. It would have been better if they'd called the big calorie a kcalorie (except for its ugly orthography) ... it would best if they'd drop it unit entirely in favour of the kilojoule. JIMp _talk·cont 00:32, 4 September 2009 (UTC)

Note also that the big calorie is "older" than the small calorie; scientists created the kilogram calorie before the gram calorie. So rather than suggesting it would have been better if they had called it a "kcalorie" or something, I'd say it would have been better if the chemists and physicists who later started to use the small unit had called it a "millicalorie".

In any case, the small calorie is rarely used any more, so there is no good reason whatsoever to use strange (and often ineffective, as Jimp has pointed out) capitalization rules to make a distinction that doesn't matter. Almost nobody does that in any case--that strange capitalization is barely common enough in actual use to even warrant mention at all in the article. It is the only large calories which remain in common use. Gene Nygaard (talk) 02:02, 31 December 2009 (UTC)

Yes, that would have been much better. Redefining stuff is a recipe for confusion. The same thing happened to the billion. JIMp _talk·cont 20:50, 15 July 2010 (UTC)

How much is 2 calories?

if one calorie heat up one liter one degree Celsius; then how many liters and degrees does two calories make? is it that two calories makes 1 liter 2 degrees hotter, or will it make 2 liters one degree hotter, or is it both? 21:56, 15 March 2010 US Eastern —Preceding unsigned comment added by Populer208 (talk • contribs)

Both. JIMp _talk·cont 09:10, 15 April 2010 (UTC)

Nicolas Flamel

Invented the calorie? Really? 98.185.253.158 (talk) 06:12, 24 March 2010 (UTC)

Which is the real calorie?

Peasaep has rewritten the intro. The current version seems to suggest that it is the gram calorie which is the "real" calorie (so to speak) and the kilogram calorie is just another unit sometimes referred to as a calorie. How true-to-life is this picture? In countries which still cling to this tired old unit aren't things often labelled using the 4.2 kJ calorie? Do we have to pick a favourite? If both are (or have been) used, why can't treat them equally? We're writing about the real world not an ideal one ... (in an ideal world there'd be no such unit anyway). JIMp _talk·cont 20:20, 30 June 2010 (UTC)

I believe "calorie" refers to a gram calorie, with "Calorie" or "kcal" referring to the kilogram calorie. See e.g. A Dictionary of Units of Measurement. I think it's a good idea to use this definition as standard and then elaborate on some of the ambiguities and incorrect usages in the body of the article, rather than compensating with vagueness is the intro. For example, the current (modified since my edit) intro states that:

The calorie is a pre-SI metric unit of energy based on the specific heat capacity of water. Definitions vary according to the mass of water used and the precise thermodynamic conditions considered.

This tries to hard to avoid using any one specific definition that it barely says anything important about a calorie. Imagine if the joule page defined a joule as "a unit of energy based on newtons, objects and meters" instead of the beautifully concise "the energy exerted by the force of one newton acting to move an object through a distance of one metre". Peasaep (talk) 12:39, 14 July 2010 (UTC)

OTOH, the Joule is well-defined, which is why it's possible to write such a concise definition; while the calorie's definition is (even ignoring the whole short/long complication) fuzzy, which makes it harder to be concise without being Wrong. (Einstein: everything should be made as simple as possible and no simpler.) Still, I grant it would probably be better to say "The calorie is the amount of energy that raises the temperature of a unit mass of water by one Kelvin." before diving into the unfortunate complications due to two choices of unit of mass and diverse choices of the temperature interval over which to measure the unit. Eddy 84.215.6.188 (talk) 15:45, 11 July 2011 (UTC)

Also, just to address some of the previous comments, I disagree that calorie always refers to kcals in the "real world". If you check pretty much any result on the first page of google results, as well as google themselves, they clearly state that one calorie is a gram calorie, equal to approx 4.2 joules (not kilojoules!). People seem to be suggesting that because some food producers incorrectly use the term calorie, we should ignore the facts and redefine what a calorie is, which is not right at all. Not only that, but most of the nutritional information I checked (e.g. the example on Food energy, the info put out by McDonalds) is printed so that it clearly indicates Calories or kcals are being used. Misuse of the term calorie certainly deserves a mention, but it shouldn't be used as an excuse to water down the opening paragraph into vague waffle. Peasaep (talk) 16:55, 15 July 2010 (UTC)

No, we are not and should not be in the business of redefining anything. The job of an encyclopædia is to reflect what is out there. If there are various different definitions floating around, this is the reality, we can't just pick the best one and label anything that deviates from this "wrong". The comparison to the joule is not really fair since the joule has a clear-cut definition. The calorie, on the other hand (or so it appears), lacks a single definition. It doesn't make for a vague waffling intro to point this fact out: this in itself is an important fact about the unit, one of the major disadvantages with using it.

Gene Nygaard (who seems pretty knowledgeable about units of measure) above states that "the small calorie is rarely used any more". He also suggests the Calorie/calorie distinction is not widely followed (and this would make sense since, grammatically speaking, it's pure nonsense: it's no proper noun). Who's right? We need something a little more substantial than Google searches and our own experiences with food containers. JIMp _talk·cont 20:50, 15 July 2010 (UTC)

Reliable sources that state "one calorie is ~4.2 joules":

• p39 of Dunford, M. and Doyle, J.A. (2007) Nutrition for Sport and Exercise
• p178 of Rastogi, S.C. (2003) Biochemistry
• p30 of Bodner, G.M. and Parude, H.L. (1989) Chemistry, an Experimental Science
• Further reasonably reliable web sources 1 | 2 | 3 | 4

Most of these sources also clearly describe the difference between a calorie and a Calorie (capital). Sources that disagree: "Gene Nygard who is pretty knowledgeable about units" and a few dieting forums. Are you really suggesting that Gene Nygard's opinion is more substantial than all of the sources that can be provided by a simple Googling?

One of the problems with trying to allow a calorie to be defined as 4.2 kilojoules is that it then suggests that it may be valid to define a kilocalorie as 4,200 kilojoules, increasing the confusion even more. It certainly deserves a mention that one of the only remaining uses for calories these days is to measure the energy content of foods, and that in this context people always mean kilocalories (even when they simply say calories), but I don't think there's any need to over-obfuscate the actual definition of a calorie. Take a look back a few years ago here, when I think the article was much clearer. It defines small and large calories, and mentions that in food energy, people are always referring to large calories. Was there anything about the old version that you found particularly objectionable? Peasaep (talk) 06:29, 16 July 2010 (UTC)

Wow, it seems to get even better the further back you go. Peasaep (talk) 07:35, 16 July 2010 (UTC)

Nutrition and food labelling is mostly where this unit still remains in use, right? In this context a ~4.2 kJ unit is implied, right? So whenever people say "calorie" they really mean "kilocalorie" and are just forgetting the "kilo-" ... no, if they say "calorie" and mean ~4.2 kJ, they're not wrong, they're simply using a different definition. I'm not suggesting we obfuscate the actual definition of a calorie: there is no actual definition ... no definitive one.

No, Gene doesn't trump reliable sources. I'm sure he'd be able to dig some up though, he must have based his opinion on something. Here's what I've found.

• http://www.trueknowledge.com/q/how_many_calories_in_joules
• http://health.howstuffworks.com/wellness/diet-fitness/weight-loss/calorie1.htm
• http://quezi.com/6403

Not that substantial, no, but it does support the propositions that the term can refer to the larger unit and that the capitalisation rule is not widely followed.

"One of the problems with trying to allow a calorie to be defined as 4.2 kilojoules ..." ... one of the problems is that we're not here to allow or disallow anything. I'm sure the article could be made clearer but it should be a clear reflexion of the real world. In the real world, like it or not, the unit is ill-defined. This is an important fact, a major cause of confusion and disadvantage with the use of the unit.

One objection to the first old version you mention was the stuff about its being a unit of heat but this is a different issue and one I've already discussed above. The older "better" version contained stuff that didn't belong here but I suppose you were looking at intro as opposed to the trivia and labelling sections. JIMp _talk·cont 08:47, 16 July 2010 (UTC)

I actually have no problem with the latter two references. I've edited again to try and take a similar approach by providing the clearest and most unambiguous information first by describing gram and kilogram calories and only then explaining the contexts under which "calorie" can refer to each. Let me know if there are still issues. Peasaep (talk) 15:48, 16 July 2010 (UTC)

I think we're moving in the right direction but, yes, there are a few things I'd like to bring up. Let me start the list with some of the more trivial.

• We've got a bit of an overlinking problem: Joule is linked to three times (four if you count the kilojoule link), International System of Units is linked to twice, Water is linked to twice, ... resolved
• Perhaps metric prefix would be better (since the calorie is non-SI) ... this is probably the better term in general but that's a different battle. resolved
• It's noted that the small calorie is exactly 0.001 large calories but the large calorie hadn't been introduced by this point. We then go on to note that the large calorie is exactly 1000 small calories ones: basically saying the same thing twice. resolved
• We're giving an "approximate" conversion to an unrelated (albeit the SI) unit before the exact conversion to a related one ("This is about 4.184 kJ, and exactly 1000 small calories.") which seems a little backward.
• Of course there isn't much approximate about 4.184 joules ... nope, that's pretty much the termochemical calorie exactly. The phrase "about 4.184 J" to me implies a give or take of 0.01% or so.
• We're no longer mentioning the variation in definition due to using water at different temperatures in the intro. If the termochemical calorie is somehow special, tell us why and mention that there are others.
• Perhaps I'm being pedantic but "the kilogram calorie is known as the 'kilocalorie'" just doesn't ring true to me. The prefix "kilo-" can be tacked on to any metric unit (unless there's already a prefix, of course) and so you could have a kilogram kilocalorie (about 4.2 MJ) ... why not? Of course, it would be uselessly big and confusing, which would explain why this is avoided. My point is that the term kilocalorie is not another name for the kilogram calorie but (as logic surely dictates) means "1000 calories", which we can pretty-much always assume are small calories. The kilogram calorie is equivalent to but not synonymous with the (gram) kilocalorie. I may be being picky but if it's clarity we're aiming at, straightening this out might even help.
• How common really is this strange capitalisation rule and is there not a clearer expression we could use instead of "referred to as a Calorie (capital 'C'), or just a calorie"?
• I notice that a couple of things are missing: the pound calorie is gone & so is some of the history (e.g. the large calorie came first).

JIMp _talk·cont 08:09, 17 July 2010 (UTC)

Could there be a typo in the FAO source?

The FAO source defines thermochemical calorie twice as 4.1840 J exactly. But when refering to the "nutritional calorie" as "basically" the thermochemical calorie, the source indicates the factor of 4.182 J per thermochemical calorie. I am thinking the 4.182 factor was a typo and that 4.184 is the correct factor. maybe.