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When You Lose Weight, Where Does It Go?
- noonespecial 11y agoI've had even worse luck trying to convince people that trees are mostly made from air and water.
- lkbm 11y agoThere's a nice Veritasium episode wherein he asks people on the street where a tree's mass comes from: https://www.youtube.com/watch?v=2KZb2_vcNTg https://www.youtube.com/watch?v=2KZb2_vcNTg (This isn't just one of those "let's laugh at how dumb people on the street are" videos; it's done explicitly as a learning exercise. His PhD looked at how addressing misconceptions and going from there to correct explanations works much better than simply providing explanations: https://www.youtube.com/watch?v=RQaW2bFieo8 https://www.youtube.com/watch?v=RQaW2bFieo8 ) I thought of it upon seeing the first chart in the BMJ article.)
- JoeAltmaier 11y agoLet me guess: mostly from water? And the air of course - carbon. Sorry, I won't watch the video, its far too spare a use of time.
- lkbm 11y agoHe pretty much just says carbon. Certainly is some water involved too, but yeah, breath in CO2 and breath out just O2.
- js2 11y agoLet Feynman explain it to them - https://www.youtube.com/watch?v=N1pIYI5JQLE https://www.youtube.com/watch?v=N1pIYI5JQLE
- knivets 11y agoThe url leads to the home page of the blog, this should be instead - https://mitchkirby.wordpress.com/2015/04/21/where-does-weight-go/ https://mitchkirby.wordpress.com/2015/04/21/where-does-weigh...
- bobowzki 11y agoIt doesn't surprise me at all... I'm an MD. I don't remember this specific piece of information being mentioned during my training. However, all the information need to reason about it was included... What really blows my mind is how many people get it wrong, including my colleagues and especially dietitians ("they had one job").
- bobowzki 11y agoThis was very recently published in BMJ. IMHO a better read than the blog post linked. http://www.bmj.com/content/349/bmj.g7257 http://www.bmj.com/content/349/bmj.g7257
- TillE 11y agoIt's fairly easy to deduce if you've ever weighed yourself at night and again in the morning. You always lose a pound or so while sleeping.
- bduerst 11y agoThe weight lost during sleeping is probably the water lost through respiration and transpiration (sweat).
- Consultant32452 11y agoYeah, but that's not really the answer most people are looking for. They're not looking for water loss, they mean the fat cells.
- barrkel 11y agoWater is a byproduct of burning fat.
- JshWright 11y agoYes, but the only part of the fat that transfers to the water is the hydrogen, which weighs just slightly more than nothing (perhaps TFA covers this... I didn't read it...)
- Doji 11y ago> Mass cannot be converted to energy except through nuclear reactions This is wrong enough to make me stop reading.
- ihodes 11y agoJust curious, how else can mass be converted to energy? EDIT/replying: I'm inclined to continue to believe that it can't in any other way. 1. Not through a chemical reaction; energy can be released in a chemical reaction, but the total mass/atoms involved remains the same. 2. Not through kinetics; energy can be produced, but mass remains the same as well. cf. some interesting caveats here http://en.wikipedia.org/wiki/Conservation_of_mass http://en.wikipedia.org/wiki/Conservation_of_mass
- glomph 11y agoAny chemical reaction?
- bobowzki 11y agoNo mass is lost in a chemical reaction.
- msandford 11y agoSpeaking in generalities yes, but TECHNICALLY stuff that contains more energy is heavier too. But given that most enthalpies are in the kJ/mole range and most moles of things are pretty heavy relative to 9e18 (the speed of light squared) that you might as well round it out and say "no mass is created or destroyed in an ordinary chemical reaction"
- peterfirefly 11y ago2H₂ + O₂ --> 2H₂O + Q Q is the released energy. If you weigh the molecules before and after very carefully, you will notice that they lose weight (or mass if you are being pedantic about it). That mass loss corresponds exactly to the Q-value (through E=mc²).
- amitutk 11y agotl;dr - "The surprising answer to this question is that we breathe it out." O₂ in, CO₂ and H₂O out
- whoopdedo 11y agoI had never thought about the question before, but now that I see it it's a "Watson" moment. My original guess would have been urine & feces.
- StavrosK 11y agoI'm proud to say that I got it right, after a brief "urine" moment, but I think it's only because I had watched the Veritasium segment about where trees come from, way back when.
- a8da6b0c91d 11y agoHow would respiration be surprising to anyone with a high school level education? > This analysis makes it clear why exercise is so powerful in the weight loss equation. There are many reasons to exercise, but it's quite clear weight loss isn't one of them. I mean, you need to exercise to get your abs to pop, but not being a lard-ass is totally about avoiding excess calorie intake and exercise really doesn't enter into it. People don't realize what a trivial amount of calories working out burns.
- recursive 11y agoIt's not clear to me. Exercise is a good way to burn calories. But perhaps more significantly, if you do it regularly, you will burn more calories even while at rest.
- Kalium 11y agoAs I understand it, the amount you can increase your caloric burn rate through exercise is generally much smaller than you can decrease your caloric intake through dieting. The result being that, as some fitness communities say, weight loss is done in the kitchen.
- Zergy 11y agoBecause the calories lost via exercise are insignificant, compatible to skipping a snack unless its very intense.
- recursive 11y agoI guess "significance" is in the eye of the beholder, but skipping a snack seems significant to me.
- DanBC 11y agoHow are you defining snack? One problem with exercise isthat it doesn't burn many calories, and some people "reward" themselves for doing that exercise with an extra bit of cake.
- loourr 11y agoIt gets dumped into the universe as heat.
- mizzao 11y agoThe energy (molecular bonds) gets dumped into the universe as heat, but not the mass (i.e. carbon atoms).
- MarcScott 11y agoAnd the reverse biochemical process is equally misunderstood. I used to teach high school Science and everyone thought a tree's mass came from the soil. http://youtu.be/2KZb2_vcNTg http://youtu.be/2KZb2_vcNTg
- yincrash 11y agoVeritasium also made a video about the article subject in 2012. https://www.youtube.com/watch?v=lL2e0rWvjKI https://www.youtube.com/watch?v=lL2e0rWvjKI
- duaneb 11y agoThis is not incorrect, a tree's mass does come partially from the soil, it's just that the majority comes from the atmosphere. It's not like the tree just puts out roots cause it likes the feeling. Where do you think all the water mass in a tree comes from? I would more chalk this up to too little biology, too late, for people to learn well. And, frankly, it's not something everyone NEEDS to know; misunderstandings are not the end of the world.
- gayprogrammer 11y ago> Where do you think all the water mass in a tree comes from? Still, we don't normally assume that water is the primary component of "soil". The key realization is that a tree is not made of the dirt around it.
- deleted 11y ago[deleted]
- madcaptenor 11y agoA quick proof that the answer isn't "you poop it out": when you work out more, you don't poop more. (You do, however, breathe more, which points towards the correct answer.)
- peterfirefly 11y agoSome of it should be peed out.
- fysac 11y agoPhysical activity speeds up the digestive process, so you do often poop more when you work out.
- gknoy 11y ago... combined with the fact that many who work out heavily increase their caloric intake (eat more). :D
- pbhjpbhj 11y agoI was thinking about this a couple of weeks ago, expiration that is. This question raised itself and I've not focussed on answering it yet - if you breathe more then, like forced breathing, can you accelerate carbon loss [beyond that expected by the increased exercise involved in such breathing]; like fanning flames I guess. Thinking now I suppose an [close] equivalent is probably can you increase carbon dioxide production by increasing oxygen saturation of the air inspired? There's probably enough in that idea to sell oxygen masks and little tanks and a book for a new fad 'diet' ...
- bobowzki 11y agoIt's not a good idea. http://en.wikipedia.org/wiki/Oxygen_toxicity http://en.wikipedia.org/wiki/Oxygen_toxicity
- pbhjpbhj 11y agoI think oxygen toxicity is pretty well know, what I was musing over was whether through a slightly elevated breath frequency, or slightly deeper breathing, one could have more oxygen available and so increase CO2 production. If instead of 100% oxygen one breathes 22% (vs. 20% in normal air IIRC), what then? Someone else has noted respiratory alkalosis as a limiting factor, but that again is seemingly an extreme.
- sp332 11y agoAccelerating carbon loss through hyperventilation will make your blood alkaline, possibly to dangerous levels. https://en.wikipedia.org/wiki/Respiratory_alkalosis https://en.wikipedia.org/wiki/Respiratory_alkalosis
- mixmastamyk 11y agoNot sure that would be true... the body is producing a set amount of CO2. Breathing faster would expel it more quickly, but not change the total amount, correct? I suppose the act of breathing itself would burn more calories, but it isn't the most challenging exercise, not to mention the dizziness mentioned already.
- Jun8 11y agoDetailed discussion: http://physics.stackexchange.com/questions/2605/how-does-mass-leave-the-body-when-you-lose-weight http://physics.stackexchange.com/questions/2605/how-does-mas... I was suprised this was not linked in the post.
- stephengillie 11y ago6 billion people, each burning 2000 calories per day equals 12 trillion calories. 6,000,000,000 * 2,000 = 12,000,000,000,000 But wait, those are Kcals. 6,000,000,000 * 2,000,000 = 12,000,000,000,000,000 1 calorie is the energy required to raise 1 gram of water 1 degree C. There are about 4404.8838 grams in a gallon. 12,000,000,000,000,000 / 4404.8838 = 2,724,248,934,784.61 So this is enough to raise 2 trillion gallons 1 degree, or raise 1 gallon by 2 trillion degrees Celcius. 2,724,248,934,784.61 / 100 = 2,724,248,934.78461 Or boil away 2 million gallons of water. Per day.
- Namrog84 11y agoany particular reason you chose 6 billion? (Just easier math?) While I thought the current estimates were closer to 7.1 billion. Though I doubt those 7+ billion people eat 2000 calories per day. When you consider how many people are starving in the world, I am not sure if its offset by the overeating overweight nations. tl;dr; why 6 billion?
- mikeash 11y agoI'd bet it's because the world population is a mesofact, and it's easy to forget that your information is out of date: http://www.boston.com/bostonglobe/ideas/articles/2010/02/28/warning_your_reality_is_out_of_date/ http://www.boston.com/bostonglobe/ideas/articles/2010/02/28/...
- asavadatti 11y agoThe author talking about the Boiling Frog myth as a fact is quite ironic in this context.
- mikeash 11y agoWell, when used as an analogy, it doesn't have to be correct. But still, you're right. While looking this up, I came across the craziest sentence in the Wikipedia article: "German physiologist Friedrich Goltz demonstrated that a frog that has had its brain removed will remain in slowly heated water, but an intact frog attempted to escape the water when it reached 25 °C." Apparently this isn't quite as crazy as it sounds, as the brainless frogs still exhibit some reflexes, to the extent that they'll jump out of hot water. But still, it reads like a study in "WTF did you expect to happen?!"
- bborud 11y agoNice try. Everyone knows that there are nuclear reactions that take place in the digestive tract and that we poop out small unobtanium lumps which are gathered in the night by underpant gnomes. that's the unknown middle step revealed. you heard it here first.
- bitwize 11y agoI think you're confusing humans with Nibblonians...
- denzil_correa 11y agoI think he is confusing reddit/4chan with HN.
- ffn 11y agoWhat about rubbing? I mean, when you rub against stuff (even wind), some of your cells get taken off. I'm all for peeing, pooping, and breathing, but how much weight do we lose just through simple friction? And if it's significant, should we employ more rubbing in our daily exercise routines?
- bkurtz13 11y agoIf rubbing and ah... friction accounted for a significant amount of weight loss, I'm sure I would be at a much healthier weight...
- maxerickson 11y agoTeh Googles say the normal rate of skin shedding is about 1.5 pounds per year. Enhancing that seems like it would lead to a lot of discomfort for a little gain.
- lingben 11y agoyour skin is your body's largest organ and one of the fascinating aspects of it is just how rapidly it both sheds or is sloughed off and just as quickly replaced
- poizan42 11y agoIANAD, but I don't think your are going to change the cell division rate in the skin that way. You will just end up performing trauma to your skin if you remove the upper layers of the skin (past the stratum corneum I think) faster than it can grow back.
- csours 11y agoNo, because it is not scalable. Your epidermis grows at a specific rate and will not really grow faster if you remove it. If you remove it faster, you will develop scar tissue, which is not desirable. An interesting way to remove fat is lactation. It is the only biologically "native" way to directly remove lipids. Unfortunately this is only available for lactating females.
- 2mur 11y ago
- joshvm 11y agoThe question is somewhat badly phrased. I think many people interpret it as "Why do I lose weight?" or even "Where does that fat go when I lose weight" and answer correctly: your body uses up your fat stores as fuel when there's no easy sugar available. Calling that a wrong answer is a bit unfair, there's nothing technically incorrect about it. However, that's not what was asked - the question is where does the mass go? After all, if you light a fire inside a box, the box doesn't get lighter. The trap is that there are by-products from the chemical reactions which have to go somewhere, and that somewhere is typically through respiration (and excretion).
- tantalor 11y agoWhen your car loses weight (fuel), where does the weight go? The exhaust, of course; your breath is your exhaust.
- mikeash 11y agoI thought it was ironic to find this statement in an otherwise solid article: "(So wrong. Mass cannot be converted to energy except through nuclear reactions)" This is, of course, wrong. All energy has mass. A charged battery has more mass than an empty one. A chunk of fat weighs more than all of the byproducts that come from metabolizing it. It's almost true, because the conversion factor between mass and energy is huge, so the change in mass for more mundane quantities of energy is far below what's reasonably possible to measure. But there's nothing special about nuclear reactions aside from the quantity involved.
- m_coder 11y agoThank you for confirming my gut response to that statement. This is very interesting.
- Mitchhhs 11y agoThanks for catching! Simplified it so hopefully i'm not saying anything incorrect now. Thanks!
- mikeash 11y agoNice! I think that simplification works nicely and gets the point across well.
- thwd 11y agoSimple counter-example: car fuel which converts to kinetic energy.
- JshWright 11y agoNo, the chemical process your car is using is almost identical to the one your cells are doing right now (oxidizing hydrocarbons). The mass of the fuel in your gas tank is pumped into the atmosphere as CO2.
- riemannzeta 11y agoThis appears to have been copied without attribution from https://www.youtube.com/watch?v=4pkSLKucVbM https://www.youtube.com/watch?v=4pkSLKucVbM
- riemannzeta 11y agoon closer inspection, this version is not nearly as good (and hence probably independent)
- MarcScott 11y agoJust asked my wife and daughter what the answer was, and they both thought you excreted the mass. Then I asked my son, who is home from Uni, studying a Biology degree, he said it was released as energy. FFS.
- drcube 11y ago>It Gets Converted to Energy (So wrong. Mass cannot be converted to energy except through nuclear reactions) This is not true. There is energy in chemical bonds, and that energy is released when the bonds break. When you burn gasoline, the mass of the resulting molecules adds up to less than the mass of the original gasoline. A tiny, tiny fraction less, but still less. Because there was energy in those bonds, and energy has mass. It's wrong in another way, too, because even in nuclear reactions mass isn't converted into energy. Mass is mass, but energy also has mass. No mass is lost in a nuclear (or chemical) reaction, it just goes somewhere else. There is no "conversion" going on.
- lurkinggrue 11y agoMovement, CO2 and urine.
- MrJagil 11y agoPlease embrace my willingness to look foolish, I really want to be able to explain this properly; can someone explain to me why fat doesn't get changed into energy, and disappear through heat?
- spott 11y ago>can someone explain to me why fat doesn't get changed into energy, and disappear through heat? Fat is some complex molecule made up of a bunch of carbons, hydrogens, and oxygens. Where do you think these atoms go? The short of it is the fat molecules are turned into other molecules (which gives you energy) with the addition of oxygen, and the byproducts (water and co2) are expelled as a byproduct.
- kgwgk 11y agoA simple analogy would be combustion in a car engine. The fuel doesn't disappear through heat. You get a number of byproducts (mainly CO2 and water) coming out of the exhaust car.
- sytelus 11y agoGreat calculation, wrong conclusion. Exercise does not cause any significant weight loss, of course unless you are doing it 6+ hours a day. All major weight loss typically comes from controlled diet. This means eliminating non-complex carbs. This is a major misconception in general public and people just don't seem to get it. Exercise helps build muscles, metabolism and endurance, but for weight loss your only practice option is diet control. The major energy expenditure for body is not walking or moving but just staying warm and brain. The reason people gain weight is not lack of exercise but because they eat all these fast burning carbs that rapidly gets deposited as fat instead of getting used up for body's energy need. If you want to lose weight rapidly, just make sure to add lot of fat and protein in your diet with as little carbs as possible and watch the weight drop.
- DanBC 11y agoHere's a meta analysis that says that exercise does help for weightloss. It also agrees with you about the health benefts of exercise, and that people get those health benefits even iftheir weight doesn't decrease. But it clearly says that exercise combined with diet changes is better than either alone. http://www.cochrane.org/CD003817/ENDOC_exercise-for-overweight-or-obesity http://www.cochrane.org/CD003817/ENDOC_exercise-for-overweig... > The results of this review support the use of exercise as a weight loss intervention, particularly when combined with dietary change. Exercise is associated with improved cardiovascular disease risk factors even if no weight is lost.
- abandonliberty 11y agoWhat's most interesting to me is that in most cases we don't gain or lose muscle or fat cells. They just grow and shrink in size.