Wikipedia:Reference desk/Archives/Science/2012 March 10

= March 10 =

Why laughter is the best medicine, scientifically speaking?
So I was wondering if there have been studies which have proved the medical benefits of laughter? I'm not asking for medical advice, just what journals say what makes laughter beneficial to health. Narutolovehinata5 tccsdnew 01:10, 10 March 2012 (UTC)


 * Presumably it has to do with the release of endorphins, reducing the effects of stress, which have a well-studied affect on health. See .  StuRat (talk) 01:13, 10 March 2012 (UTC)

There is a substantial literature on the medical benefits of laughter. A Pubmed search for "laughter therapy" finds over 350 articles; is a recent review. A lot of the research was motivated by a book by Norman Cousins called Anatomy of an Illness As Perceived by the Patient, in which he described the use of laughter therapy to treat a very serious illness. Looie496 (talk) 03:10, 10 March 2012 (UTC)


 * The reason for laughter at all seems more than a bit mysterious to me, but our article on laughter in animals is more than a little interesting. Rats?  Now that's funny!  I've wondered if laughter could be a sort of show of disarmament, like a handshake - by laughing, a person (or animal?) makes clear that air intake is being limited, and therefore, a robust fighting response is unlikely.  But I still have no real idea. Wnt (talk) 06:40, 11 March 2012 (UTC)

How about neither the Wright Flyer nor the 14-bis?
A question about the invention of airplanes was asked last September, and of course there's not a simple answer. The honor of the first real airplane seems to have coalesced for some into two candidates: the 14-bis or the Wright Flyer. I guess the pertinent criteria are that the aircraft's flight be manned, powered, sustained, and controlled. Apparently, the 14-bis fails on the latter two, while the Wright Flyer used a catapult to take flight and did not launch under its own power. So the decision between the two planes is a decision of whether one thinks an unassisted launch is more important than a controlled flight. But what if we ditch both of these candidates? Then which aircraft fulfills all of the criteria? Surprisingly, I found it difficult to find the answer to this even though there seems to be plenty of info both on Wikipedia and generally on the web. TresÁrboles (talk) 01:12, 10 March 2012 (UTC)


 * Note that if using a catapult launch system disqualifies an airplane from being "real", then most airplanes launched off of aircraft carriers must be fictional. StuRat (talk) 01:19, 10 March 2012 (UTC)


 * But they wouldn't be first. TresÁrboles (talk) 01:22, 10 March 2012 (UTC)


 * Sorry, I withdraw my above response; it doesn't make sense! TresÁrboles (talk) 01:27, 10 March 2012 (UTC)


 * Yea, I agree. I was just pointing out the absurdity of claiming that a plane launched from a catapult is somehow not real.  Incidentally, the requirement of it being manned also seems wrong, as many remote-controlled airplanes are also "real".  However, at that time, the only way to have controlled flight was to put a person on-board. StuRat (talk) 01:29, 10 March 2012 (UTC)
 * The difference being that the catapult launch is used aboard aircraft carriers in order to permit takeoffs from very short runways with high takeoff weights (extra fuel and armaments). An F-18 can still take off quite comfortably without any catapult from a regular land-based runway. TenOfAllTrades(talk) 01:54, 10 March 2012 (UTC)

Would it perhaps be the Blériot VI (or later versions)? Or maybe the AEA June Bug? The problem with accounts of these early aircraft is that they will tell you about length or durations of flighs, but they're not very good at discussing sustained or controlled flight (which admittedly bring a little subjectivity into the mix). TresÁrboles (talk) 01:22, 10 March 2012 (UTC)


 * I'd like to know where the OP got the idea that the Wright flyer was launched using a catapult. There's nothing about it in the article, and in fact I've never heard that before. The launching rails were 2-by-4s mounted in the sand in order to keep the flying machine steady as it built up speed before takeoff. In fact, according to Wright brothers, they didn't use a catapult until the fall of 1904. In any case, this kind of argument is a bit like claiming that Bell didn't invent the telephone because it didn't have a dial on it. ←Baseball Bugs What's up, Doc? carrots→ 09:04, 10 March 2012 (UTC)
 * Later (albeit early) Wright aircraft launched with catapult assistance; we have a picture in the Wright Flyer III article that notes the catapult was used starting in September 1904. This is, of course, nearly a year after the first successful flight of the Wright Flyer. &mdash; Lomn 19:05, 10 March 2012 (UTC)


 * Sorry, some sloppiness on my part; I read about the debate on the afore-mentioned WP page and also here and didn't notice that they were talking about catapults ("ground aceleration device") or rail. Anyway, are we saying that the Wright Flyers could've done without the rails or catapult if they had wanted to? Well, whether true or not, it seems that in fact they weren't unassisted for whatever reason. TresÁrboles (talk) 06:15, 11 March 2012 (UTC)


 * I've always thought of the Wright bothers as being the first to develop a workable powered aeroplane, because they were the first to work up a sound design through the professional engineering approach based on sound research (eg using an instrumented wind tunnel) - their approach meant that so long as they kept at it, their development of a sound aeroplane was inevitable. Others at the time were more hit-or-miss/good luck.  Later workers had the Wright's knowlege and experimental techniques to build on.  Ratbone58.170.179.120 (talk) 11:57, 10 March 2012 (UTC)
 * You're onto it. Their scientific approach was discussed at some length in TV specials around the anniversary in 2003. And keep in mind that what they really did was to develop a practical propellor engine and put two of them on a glider. Inventions don't arise from nothing, they build on what came before. ←Baseball Bugs What's up, Doc? carrots→ 13:25, 10 March 2012 (UTC)


 * I'm not knocking the importance of any party's contribution to aviation, just curious as to which heavier-than-air aircraft, apparently neither the Wright Flyers nor the 14-bis, demonstrated the first manned flight that was powered, controlled, and sustained, without aid of outside launch devices like catapults or rails. TresÁrboles (talk) 06:15, 11 March 2012 (UTC)
 * There's a major difference between a catapult and a rail. I suppose they could have put wheels on it, but keep in mind they were taking off from sand dunes, so wheels wouldn't have been very practical. ←Baseball Bugs What's up, Doc? carrots→ 09:53, 11 March 2012 (UTC)


 * I can see some sense in excluding an aircraft launch from rails and not ever designed to have wheels, because only with a capability to take off or land with wheels does an aircraft have the potential to become utilitarian. Thus wheels are an essential development feature to some extent like turn and bank controls and engines.  Only to a certain extent though - flying boats were certainly a useful thing in their day - and no wheels at all on many of them.  However "sustained" needs clarification.  If sustained means remaining aloft under controlled flight until either the pilot is tired, or fuel runs out, or the pilot makes an unforced decision to land, then the Wright Brothers demonstrated sustained flight first - even if their early flights lasted only minutes.  Ratbone58.167.249.105 (talk) 13:50, 11 March 2012 (UTC)


 * I think it's clear that a person can draw an arbitrary dividing line to make whoever they want "first" to cross it, but it has little significance. I'm tempted to give Emperor Wenxuan as much credit (see Man-lifting kite) - it required the right weather conditions, and was not safe, but the same could be said of any of those early experimental planes, just less so. Wnt (talk) 15:32, 11 March 2012 (UTC)

3D printing for integrated circuits
Is it theoretically possible for 3D printing or a similar technology to advance to the point where it can produce integrated circuits at a small enough transistor pitch to outperform FPGA implementations? Neon Merlin  03:27, 10 March 2012 (UTC)


 * This question is a bit like asking Henry Ford in 1920 if the development of automatic machine tool lines will enable production of a car so good it will outperform the Model A. The two (the tool and the product) are not in any way directly related. 3D printing currently is about depositing a homogenous material (plastic or metal) layer by layer to build up a part. The production of semiconductors is not production of homogenous materials - they are complex structures of many different semiconductor, metal, and insulator layers, not counting the necessary passivation, and the necessary lead bonding and packaging.  However, advanced researchers are currently using tools that can place material atom by atom (probably at an enormous cost per atom!), so I suppose if you stretch both your imagination and the definition of 3D printing, it might be possible at some future time to use this to build up an integrated circuit.  More importantly, the performance of current FPGAs' is far more likely to be incremenatally improved by more conventional evolution of Xray lithography and the like.  By the time any 3D printing-like technology is anywhere good enough, FPGA's will likely be well and truely obsolete.  Ratbone58.170.179.120 (talk) 11:46, 10 March 2012 (UTC)


 * Because of its goals, some people involved in the RepRap Project have tried developing methods to produce circuit boards, and also pick and place toolheads but they haven't really be that successful, particularly I think with the circuit board (due to the lack of an effective and fairly safe method of making one). Of course this is still very different from producing ICs. Nil Einne (talk) 15:26, 10 March 2012 (UTC)


 * Useless crowd, that sort of thing was done back in 1947 . Dmcq (talk) 17:47, 10 March 2012 (UTC)
 * Perhaps. But Sargrove's sprayed circuit system never made it to comercialisation because too many compromises were made - the performance of anything built could not compete with conventional circuits. It was a step backwards. But at about the same time, the American National Beaurough of Standards came up with a fully automated system based on ceramics - Project Tinkertoy.  This was a sound idea, a step forwards, fully flexible, and reached limited comercialisation before being overtaken by transistorised printed circuits. Unfortunately there is no Wikipedia article on this fascinating and amazing system. See http://www.radiomuseum.org/forum/usa_project_tinkertoy.html  Today, of course, robot production of electronic products is routine, even for low volume products.  But All these things, from Sargrove's sprayed circuits, tinkertoys, and today's robots, are not "meta" tools - the machines do not resemble what they make and they cannot make themselves.  The ReRap project seeks to be so flexible it can make anything, even itself.  The implications are profound.  You want a widget?  Download the file and run it - out pops a widget.  Whole industries based around parts sourcing, warehousing, and sale could eventually dissapear.  Keit60.228.241.4 (talk) 02:28, 11 March 2012 (UTC)
 * From Dmcq's source:
 * As the panels passed through, they were grit-blasted, sprayed with metal and graphite, milled, lacquered and tested, emerging twenty seconds later ready for final assembly on the bench.
 * After spraying with metal the panels passed into the face-milling unit. High-speed diamond tools removed metal from the upper surfaces, leaving it in the grooves and depressions. A second spraying followed, this time with a resistive material such as graphite. The various eyelets, valve bases, potentiometer arms and other components needed were then pressed in automatically. The panel was sprayed with lacquer, and finally the circuits were tested.
 * None of this sounds like the sort of thing that suitable for a sub US$1000 (reaching sub US$500) machine which ideally even someone without much experience (e.g. in the developing world) can make themselves and then use safely. (Bearing in mind also the goal of the machine being able to make itself and the immediate subgoal producing as many parts on the machine as possible and at a resonable price.) So I'm not particularly sure of the relevance of your example.
 * I mentioned the problems making PCBs, there are plenty of suggested methods like laser etching (although to me this sounds like a better idea for at home usage then gritblasting), chemical etching (perhaps with a person doing the etching part and the machine just making the traces) some of which are already done either commercially or even at home (using inkjet printers for example). But these don't generally receive that much attention because safety wise they can't considered great options. (For other alternatives like printing circuits with Field's metal, the problem is at least partially concern over how well these circuit boards would work and hold up.)
 * Of course as Keit mentioned there are plenty of existing commercial tools which do all this and more, however they often aren't intended for someone to use at home, nor to make themselves. (Even most truly commercial rapid prototypers are still over US$10k.) However if you believe you've some idea of how to do things better, you're welcome to join the project which mostly follows the FLOS ideals. I would say that from what I've seen (I'm not really involved but have been monitoring it for a while), somewhat akin to the way things happen here on wikipedia, plenty of people have brillant ideas. When it comes to implementing them at a resonable price and in a manner that most people can follow safely, they find it's not so simple.
 * P.S. I was having trouble finding a suitable summary link yesterday for circuit boards but I now found
 * Nil Einne (talk) 05:43, 11 March 2012 (UTC)

scientifically, which deoderant is best?
you know how for toothbrushes and toothpastes, dentists will have a recommendatin. well I'd like to draw an analogy, but I don't know the profession. anyway, scientifically which deoderant is best? --80.99.254.208 (talk) 19:16, 10 March 2012 (UTC)
 * I doubt there is any reasonably unbiased consensus scientific opinion. Likewise, nebulous "dentists recommend X toothpaste" marketing fluff should not be confused with a scientific declaration that X is best; I doubt any such opinion exists for those products, either.  &mdash; Lomn 21:29, 10 March 2012 (UTC)
 * Is Consumer Reports in the pocket of marketers? Is not testing products and being an objective source of at least less biased quality data their stated goal? From the article I provided a link to: "Consumer Reports is an American magazine published monthly by Consumers Union since 1936. It publishes reviews and comparisons of consumer products and services based on reporting and results from its in-house testing laboratory. It also publishes cleaning and general buying guides. It has approximately 7.3 million subscribers[1] and an annual testing budget of approximately US$21 million" It has an annual testing budged of approximately US$21 million. Maybe some of that was used to test deodorants. Maybe not. I don't know. But it seems like they have a source of money and they could be construed by the average juror in a US court to (as a magazine) claim to offer "reasonably unbiased consensus scientific opinion" (to use Lomn's words). So there's the threat of legal action prompting Consumer Reports to actually do something that approaches reasonably unbiased consensus scientific opinion in a market they already claim to service (consumer products, of which deodorant is a common part). 20.137.18.53 (talk) 17:59, 13 March 2012 (UTC)


 * The cynic in me would say that dentists probably recommend the brand that pays them the most to do so. Hopefully they have enough professional ethics not to recommend something that is actually rubbish, but I doubt there is really much to choose between them so the commission they get is probably the key factor. (That's definitely going to be the case for the dentists in adverts giving recommendations - that's assuming they are really dentists at all.) I guess the place to go for a medical opinion about deodorant would be a dermatologist, or perhaps just a GP/family doctor. I'm not sure they would have much to say, though. If you are having significant problems with excess sweating or odour, then you should speak to a doctor because there may be things they can do to help. --Tango (talk) 21:27, 10 March 2012 (UTC)
 * Toothpaste companies statistics are the frequently used example in How to Lie with Statistics – a book, which despite its age, they seem to stick to! Accordingly, the answer really is that deodourant companies market their product differently. You might get some statistics, though, but they're probably customer recommendations rather than scientific statistics. Grandiose (me, talk, contribs) 21:34, 10 March 2012 (UTC)


 * There are possible side-effects of some of the nasty chemicals in them, like skin tags. However, I assume you are asking about which works the best, not which has the least side-effects.  First, let's make sure you understand all the terms:


 * "Deodorant" is just perfume to cover up the smell.


 * "Antiperspirant" actually prevents sweating, and, since sweat is where the bacteria grow, this can prevent odor, too.


 * "Antibacterial" kills the bacteria, too.


 * Many products combine these methods. Then there's the form to consider:


 * Sprays can cause you to inhale some, and that's not good.


 * Solids tend not to get under all the pit hairs, so not good for those with hairy pits.


 * Roll-ons and gels deliver a liquid which can flow under the hair.


 * And, as far as preventing staining of the clothes, a clear gel seems best there. StuRat (talk) 21:36, 10 March 2012 (UTC)


 * Sprays are anti-social, and should be banned until a process is found to ensure that none of the spray reaches another person. HiLo48 (talk) 00:06, 11 March 2012 (UTC)


 * Then there's always the option of moving to France, where they just douse themselves in perfume and think it's good enough. StuRat (talk) 00:27, 11 March 2012 (UTC)


 * ?skin tags, I think we ought to have a a citation for that Stu. There is nothing in the article that suggests 'nasties' in deodorants cause skin tags. They occur on several parts of the body that are not subject to deodorants. Putting "possible" in doesn't reduce the impact for the nervous. In my several decades of OR, different deodorants react differently with different people and it may prove difficult to find "the best" product. What you may find after some trials is the best product for you. The excellent advice above about various forms of deodorants ought to help you get started. Don't listen to advertising!! Richard Avery (talk) 07:51, 11 March 2012 (UTC)


 * Not sure if anyone has ever bothered to research it yet, but here's an admittedly nonscientific site where they talk about a possible link: . StuRat (talk) 02:51, 12 March 2012 (UTC)

Defrosting shrimp
I have a package of frozen cooked shrimp. The package says "Do not force thaw under running water". Any idea why this would be a problem? Is a safety or a quality issue? ike9898 (talk) 19:16, 10 March 2012 (UTC)


 * That question seems to have been asked a number of times (just google it). The responses all seem to be of the opinion that slow thawing (in a fridge) reduces moisture loss. To me, that sounds ridiculous; allowing food to just sit (anywhere) seems a recipe for letting it dry out. Put your shrimp in a bowl (in the sink) and fill it with cold water. Allow cold water to very slowly trickle into the bowl to keep the water moving (and spilling out into the sink) and it will be fine. Just use/consume it when it's ready. Above freezing temperatures, shellfish do not improve with age. Matt Deres (talk) 20:57, 10 March 2012 (UTC)


 * I assume they ask you to thaw it in the fridge inside the sealed package, which prevents moisture from evaporating. StuRat (talk) 22:07, 10 March 2012 (UTC)


 * the instructions given on the package conform to HACCP Hazard analysis and critical control points--Digrpat (talk) 21:51, 10 March 2012 (UTC)


 * I suspect the problem with thawing it in water is that people forget about it, then discover it hours later after the nasties have had a chance to grow, but eat it anyway. If you thaw it in the fridge and forget about it, at least it will be kept cooler. StuRat (talk) 22:10, 10 March 2012 (UTC)


 * This seems... unlikely to me. Who tries to force thaw shrimp hours before eating? --Mr.98 (talk) 23:33, 10 March 2012 (UTC)


 * Do you just stand and stare at your shrimp as it thaws ? If it take more than 30 seconds, I would walk away, then I might look at a Ref Desk Q, and need to spend the next several hours finding enough references to prove that air contains oxygen, say, lest I be accused of original research. :-) StuRat (talk) 05:49, 11 March 2012 (UTC)


 * One major issue might be that shrimp is very sensitive to temperature. I've seen shrimp start to turn pink under just a little bit of lukewarm water. You don't want to overcook shrimp. --Mr.98 (talk) 23:33, 10 March 2012 (UTC)


 * I wonder if this is a taste thing rather than a science thing. I'm not a fan of cocktail sauce but eat shrimp as a low-calorie treat dipped in a bit of hot butter, and I thaw it in hot water all the time.  I think leaving it in water too long could soak out some of the good flavor, but maybe some people notice the leaching of flavor with even a momentary soak? Wnt (talk) 00:45, 11 March 2012 (UTC)

OP here. I'm talking about pre-cooked shrimp, so getting cooked under hot water is really not the issue. Also shrimp thaws quickly, even in cold tap water. It's not something you'd be tempted to walk away and forget about. Leaching of flavor seems plausible to me. Also, this is from a Costco bag of shrimp, the size that many consumers will not use all at once, and will thaw one portion at a time, not in the original package.

I'm not sure we have a definitive answer yet. ike9898 (talk) 01:32, 11 March 2012 (UTC)


 * Done it both ways (in the fridge and in cold tap water) and wasn't able to detect any difference. I'll add that when defrosting in cold water I keep an eye on things and remove from water as soon as defrosted but still feel a bit guilty of something. hydnjo (talk) 01:52, 11 March 2012 (UTC) BTW, defrosting in cold water will dilute out some of the sodium tripolyphosphate which is a good thing :-) hydnjo (talk) 02:37, 11 March 2012 (UTC)


 * It seems to me this 'many consumers' thing is perhaps a key point. It may be true that many consumers are like you and will only thaw a small number. But how large is the bag? 1kg? This may be large, but it also seems likely some people will want to use the whole thing. And while thawing the small number you use may happen quickly, thawing a 1kg bag is likely to take longer and could easily lead to the area of common concern where the outer portion is already thawed and depending on the temperature of the water, reaching temperatures consider unsafe, but the inner portion is still frozen. Nil Einne (talk) 05:19, 11 March 2012 (UTC)


 * If you have a big bag, then ideally you only want to thaw the portion you intend to eat. If it's all frozen together as a giant block of ice, this may not be possible.  In this case, thawing in the fridge until you can break off a chunk will keep the rest from getting too warm. StuRat (talk) 05:49, 11 March 2012 (UTC)

Does hot food have more calories than cold food?
Title says it all... Whoop whoop pull up Bitching Betty 22:17, 10 March 2012 (UTC)


 * I don't see why it would. However, cold food will require you to burn a few more calories, to bring it up to body temperature, and may digest a bit more slowly, until it does reach body temp. StuRat (talk) 22:29, 10 March 2012 (UTC)


 * No. When we speak about "calories", we mean energy stored in chemical bonds that can be released by digestion and metabolism. Heat energy doesn't count. Dominus Vobisdu (talk) 22:30, 10 March 2012 (UTC)


 * One thing that might influence it though, is how the food was heated. That is, was any compounds like oil, grease, or fat, etc. removed or added during the heating process. -Laniala (talk) 22:34, 10 March 2012 (UTC)


 * I think it does - after all, Antarctic explorers have been reported to burn as much as 10,000 calories daily due to the intense cold. For them, at least, any warmth gained from the food is warmth that doesn't need to be produced by shivering, brown fat, or other bodily processes.  However, this wouldn't apply to someone who becomes hot enough to be sweating (at least to a very crude approximation).  Also, it's not really very much - imagine, for example, how a cup of sugar would melt and flare when burned, for example in a fuel with potassium nitrate.  By comparison the heating is a pretty small amount of energy - one capital-C Calorie is the energy to heat a full kilogram of water by 1 C, and it would heat most things by more than that. Wnt (talk) 22:45, 10 March 2012 (UTC)

I think it's also worth quantifying StuRat's "a few more calories" in some way. Let's say that one person eats exactly 1kg of protein that is at 4 degrees C (e.g. it had just been removed from a refrigerator). A second person eats exactly 1kg of protein that is at 20 degrees C (e.g. at room temperature). A third person eats exactly 1kg of protein that is at 35 degrees C (e.g. it is "warm" or "hot").

Now, if I remember my biology lessons correctly, protein has 17kJ of energy per gram (This might be absurdly wrong, please correct me if so). So the calorie content of this great big protein meal (ignoring the heat energy) will be 17,000kJ in each of the three cases, right? The first person needs to raise the 1kg by approx 33C to get it to body temperature, the second person needs to raise it by approx 17C, and the third person needs to raise it by approx 2C. Assuming each of the three people do in fact raise the 1kg to body temperature before excreting or exhaling any of it, how much energy does it require in each of the three cases? I think it would make an interesting comparison between the food value and the heat values involved.

Of course, as other posters have said, uncooked or "raw" food can have greatly different qualities to cooked food. (For one thing, a raw carrot probably has some more fibre content than a carrot that's been liquidised and cooked and made into carrot soup.) --Demiurge1000 (talk) 22:48, 10 March 2012 (UTC)
 * It takes about 70 kJ to raise the temperature of 1 kg of liquid water 17C (and twice that for twice the temperature change). I don't know what the heat capacity of protein is, but it's probably lower than that of water, so the price of heating the food is small compared to its stored energy. Rckrone (talk) 05:32, 11 March 2012 (UTC)

Hmmm, it also occurs to me that water expands by roughly 0.15 parts/1000 per degree C at physiological ranges - so if it were measured out by volume after heating, a 4000 kcal kilogram of protein, if suspended in water or otherwise acting like water in terms of expansion, would lose 0.6 Calories per degree Celsius, while gaining 1 Calorie from the heating. I'm not sure about Demiurge's point that cold food must be heated - if a person is sweating to lose energy anyway, then I don't think that heating cold food that is eaten actually increases the body's metabolism. But I could be wrong about that - it could respond that way. Wnt (talk) 00:29, 11 March 2012 (UTC)

I am afraid the title doesn't say it all. Do the OP mean "Does a dish contain more calories when served hot than when served cold?" or "On average, does the type of dishes that one would normally serve warm contain more calories than the type of dishes that you normally serve cold?". There is a difference, and of course if it is the latter one would have to specify which cuisine, since it varies greatly. --Saddhiyama (talk) 00:46, 11 March 2012 (UTC)


 * The former. Whoop whoop pull up Bitching Betty 02:18, 11 March 2012 (UTC)


 * ... and, of course, if the heating is from significant cooking, then the cooking process makes many foods more readily digestible and thus possibly yielding more calories.   D b f i r s   07:34, 11 March 2012 (UTC)


 * I think it's two things answered here. The energy in the food itself (Calorie is just a unit for energy), and the body's ability to absorb this energy.
 * 1) The amount of calories food will have at two different temperatures, assuming they are exactly identical in form, shape and substance at both temperatures. (Which probably will rarely be the case in practice, but in this "theoretical" case I agree with Dominus Vobisdu's answer at the beginning.) 2) The second thing, which seems to be most discussed here, is how much of this energy the body will be able to absorb and make use of when the food is at different temperatures.  To make it a bit more complex in real life, food often can lose substances (for example moisture through evaporation) or somebody adds substances indirectly (maybe soot from a cooking fire) or directly (water, cooking oil, grease, etc) when it is heated up.  Heating also tends to, as also written above, change the shape of the food .  All of which might influence the body's ability to absorb the energy present in the food.  -Laniala (talk) 22:17, 11 March 2012 (UTC)


 * It's true that preparation can change the calorie count of foods, presumably if it causes a chemical change in the composition (I'm assuming it will keep its increased calories even if refrigerated afterward though). Also, even the exact same food can have different calorie counts for different people. Wnt (talk) 00:05, 12 March 2012 (UTC)