12 ms·
When somebody loses weight, where does the fat go?
- pianom4n 9y agoThere's a TEDx talk about this: https://www.youtube.com/watch?v=vuIlsN32WaE https://www.youtube.com/watch?v=vuIlsN32WaE
- gebeeson 9y agoThanks for posting that link - after reading the article, that video was the first thing I thought of. It's a great talk that is simple to understand.
- krallja 9y agoReminds me of the question “what are trees made of?” (The answer to both questions is “mostly atmospheric CO2.”)
- k__ 9y agoHehe, true. I once saw a documentary about "big animals" in the past. Like, why did we have giant spiders and insects while they have a rather simple respiratory system that doesn't scale very well. Because: trees! Somehow plants managed to create wood, which bound the C from CO2, but the rest of the biosphere didn't know what to make of the wood. So there were more and more trees and more and more C got removed from the atmosphere. A much bigger part of the atmosphere was O2 and so the insects could grow bigger. But in the end the fungi figured out how to make short work of wood and in turn released much of the C again into the atmosphere as CO2, so the animals shrunk again.
- Cd00d 9y agoI thought ants were what made short work of the wood. Something about formic acid? Do you know more - I need to reset my ignorance.
- dandare 9y agoThat is very interesting. Is it related to coal? Will the trees today nor form coal because they will be processed by fungi?
- masklinn 9y ago> That is very interesting. Is it related to coal? Will the trees today nor form coal because they will be processed by fungi? No, coal has formed after fungi found how to break down lignin (lignite is usually "young" coal, having generally formed between the disparition and the dinosaurs and modern day, generally speaking the better the coal the older it is as coal is a metamorphic process, so given similar conditions time is the factor for the rock going through the grades), lignin isn't the only organic component even in carboniferous coals, and these coals have lignin-rich and lignin-poor epochs and locations. And peat lands exist today which perform the first "step" of coal formation. The trees today are unlikely to form coal because that first requires quickly putting the trees in anoxic conditions (e.g. acidic waters or low-permeability soils) over a sufficiently long time that good-sized layers can build up, then shifting those layers way down so they can be converted by heat and pressure over millions of years. Carboniferous had lots of low-lying forested wetlands and swamps which provided the vegetable matter in anoxic conditions, and the subduction zones of the forming pangea proceeded to shove much of it under (when both happened in the same place), that is why it's the source of so much coal. But few of our peatlands are in subduction zones, and even if they were it's unlikely we'd give them the time to accumulate and slide down for processing.
- ultratopo 9y agoDo you remember the name of the documentary?
- k__ 9y agoNo sorry, this was probably 10 years ago and in German.
- mikeash 9y agoFor anyone coming straight to the comments looking for an answer to the question: it turns into CO2 (and a bit of water) and you breathe it out. When you realize that you have to breathe out all the weight you lose, I think it gives you a bigger appreciation for how difficult weight loss can be.
- JoeAltmaier 9y agoExercise makes more sense! Breathing hard == losing weight!
- Zanta 9y agoFrom the paper "Replacing one hour of rest with exercise that raises the metabolic rate to seven times that of resting by, for example, jogging, removes an additional 39 g of carbon from the body, raising the total by about 20% to 240 g. For comparison, a single 100 g muffin represents about 20% of an average person’s total daily energy requirement. Physical activity as a weight loss strategy is, therefore, easily foiled by relatively small quantities of excess food."
- misterdata 9y agoThe question is whether the body spends any energy outside of that hour after exercising (e.g. by growing muscle, etc.) than it would otherwise. That would make exercise more effective when considering longer periods of time.
- s0rce 9y agoIt is "burned" basically the same as if you lit it on fire, it converts to CO2 and H2O.
- JshWright 9y agoAn interesting corollary to this is "Where do trees get their mass?" Veritasium has a fun video demonstrating how unintuitive this is: https://www.youtube.com/watch?v=2KZb2_vcNTg https://www.youtube.com/watch?v=2KZb2_vcNTg
- StavrosK 9y agoI love that you used the word "unintuitive" rather than imply that people were uneducated for thinking it. Good way of thinking about knowledge.
- lostconfused 9y agoBecause it's not that simple. Every moment of a person's life adds to their sum total of knowledge but it's very limited. Simply being a living human isn't going to give you a good understanding of quantum mechanics or general relativity, but it will give you some basic idea of things falling towards the ground. Something being unintuitive doesn't mean just that the individual lacks knowledge but that there is very little chance that this knowledge would be encountered in ones life time at all without making an effort to gather a deeper understanding.
- s0rce 9y agoWhy is CO2 the correct answer, the answer should be energy/heat + CO2 + H2O? The "burning" of fat in oxygen to CO2 and H2O is exothermic.
- Xophmeister 9y agoTFA does say "energy/heat + CO2 + H2O", but most of the output in terms of mass -- which is what one is interested in when it comes to losing weight -- is carbon dioxide.
- mtzaldo 9y agoDoes this means that we can "control" entrophy in the universe by controlling the CO2?
- colechristensen 9y agoThe fat molecules burned usually have about twice as many hydrogen atoms as carbon atoms so you end up with about as many CO2 molecules as H2O molecules. Carbon weighs about 14 times as much as hydrogen and most of the oxygen in both comes from the atmosphere. So when you lose weight, 7 parts go to CO2 and 1 part goes to water. A very very tiny proportion goes to energy with mass-energy equivalence.
- zimbu668 9y agoFrom the abstract: "Most people believed that fat is converted to energy or heat, which violates the law of conservation of mass."
- orblivion 9y agoBut not the conservation mass-energy. What's to say we're not burning off our fat in a nuclear reaction? :-D
- colechristensen 9y agoChemical reactions undergo the same mass loss as nuclear reactions. A fat molecule weighs very slightly more than the sum of it's parts. The resulting water and carbon dioxide products will weigh less than the reactants by exactly the amount of energy released. It's just much more difficult to notice because the amount of energy released is as much less.
- pwinnski 9y agoObservations from Figure 1, "Responses of a sample of doctors, dieticians, and personal trainers to the question “When somebody loses weight, where does it go?”" 0 doctors were willing to admit they didn't know. 0 dieticians thought sweat was involved. Those results seem unsurprising. Only dieticians correctly answered CO2.
- arkades 9y agoOverstating the case about “0 dietitians ... only dietitians.” It looks as though about 2 people thought sweat was involved, and only 1 dietician answered co2. Pretty much everyone answered “heat.” The question itself is shit, too, which is what happens when you dont have survey epidemiologists eyeball your questions. In “losing weight,” you’re doing a number of things - chucking the actual carbons (mass), and removing the potential energy stored as carbon-carbon bonds (heat). Given the widespread colloquialism of “losing weight,” people failing to interpret it as regarding the removal of carbons specifically isn’t unreasonable. Sweat and urine are also correct answers, for that matter. Some of the carbon is used to create bicarbon and carbonic acids, via co2, which are lost in urine and sweat. Whether you want to count that as co2 or not is an argument about semantics - it goes through co2, but isn’t lost -as- co2. Of course, from the perspective of “it’s all breathed out as the result of perfect oxidation,” it’s wrong... but why let biology get in the way of undergraduate chemistry, right? This isn’t a reflection on docs, PTs, or dietitians. This is GIGO.
- eeZah7Ux 9y agoI'm pretty aghast at the ignorance of the survey participants and how they failed to admit it. From doctors, this should not happen.
- revelation 9y agoYou ask an ill-specified question and get an ill-specified answer. Of course that fat "goes into" energy/heat, it says so right in the oxidation process. It's an interesting reiteration of HS chemics, but of no practical concern.
- somebee 9y agoThis is one of my all-time favourite fun facts. First learned about it in Tell Me Something I Don't Know: http://freakonomics.com/podcast/tell-me-something-i-dont-know-a-new-freakonomics-radio-podcast-2/ http://freakonomics.com/podcast/tell-me-something-i-dont-kno...
- ZeWaren 9y agoIt's pretty obvious when you do long fasts. Every time I fast for more than I week, I lose several kilos doing nothing, not going to the bathroom even once except to pee.
- DoodleBuggy 9y agoWhat is your intake during the fast? Bone broth? Water? Electrolytes?
- DoodleBuggy 9y agoThe TLDR: > Physical activity as a weight loss strategy is, therefore, easily foiled by relatively small quantities of excess food. > Our calculations show that the lungs are the primary excretory organ for fat. Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often heard refrain of “eat less, move more.” "Eat less, move more." If anyone isn't aware of that by now, I don't know what to say.
- DanBC 9y agothe eating less part is more important (for weight loss) than the moving more part, especially because people doing exercise for weight loss often overestimate how many calories the exercise is burning, and underestimate how many calories are in food.
- wccrawford 9y agoPlus, the difference between "not losing weight" and "losing weight" can be a lot of calories. If you were gaining weight regularly and start exercising to lose it, you'd have to do a ton of exercise to compensate. But if you're on the verge of losing weight and start exercising, it would be possible to tip the scales, so to speak. So long as you don't start eating more because of it. I'm 205 lbs, and the charts say I need to eat between 1500 and 1800 calories per day to lose weight. I can eat 2600 and maintain my weight. So if I'm just barely maintaining my weight at 2600 calories and I want to lose weight, I'd need 800 calories worth of exercise. Moderate-pace walking burns 300 calories per hour for me. I'd need almost 3 hours of deliberate walking at a good pace to lose that extra weight, every single day. And I couldn't reward myself with a treat afterwards. I got the exercise numbers from MyFitnessPal. The food calories I got from a site I found the other day, but I don't remember which.
- DoodleBuggy 9y agoIt's often willful ignorance, combined with most people not wanting to actually give up a vice.
- fleitz 9y agoYeah, it's more like body composition than 'weight loss', most people want more muscle / less fat, and then eat a diet that produces more fat and less muscle. People act as if Arnold got his body by once accidentally picking up a barbell, then eat a bunch of food that immediately gets converted into fat and wonder why running on a treadmill to destroy their muscle & eating sugar to produce fat isn't giving them the results they want.
- corpMaverick 9y agoI am confused by this... > We suspect this misconception is caused by the “energy in/energy out” mantra and the focus on energy production in university biochemistry courses. I understand from the article that chemistry (Which I can't understand) tells you that it is converted on CO2. But still. Clearly I can move because I have energy that I acquire from food. How is this wrong ?
- wyufro 9y agoTheir point, which I agree is fairly unclear, is that the fat is not converted to energy, it's converted to CO₂ and water. That conversion releases energy, which you then use to move, but the total mass of the process is constant (conserved).
- gwright 9y agoJust to add a bit of clarification, the excess energy part of the equation is coming from the energy stored in the chemical bonds of the original molecules. The chemical energy of the original molecules is more than the chemical energy of the resulting molecules leaving some energy to do work and to generate heat.
- bluGill 9y agoThat release of energy does result in mass loss. e=mc^2 as everybody knows, without understanding. However the energy is fairly small, and c is already extremely large before you square it. Over an entire lifetime the mass loss is still insignificant.
- jasamer 9y agoIt is not wrong. It just doesn't tell you anything about where the mass goes.
- yodon 9y agoAt the risk of crossing the streams here... “wait! HN must be listening to the Microphone on my phone because I talked with my son about this exact topic 36 hours ago and now it’s in my HN feed!” Yes, that’s a joke, but it’s also a completely factual statement (except for the Microphone thing) and a good reminder that with enough page views even extremely low probability events will happen with great frequency and predictability to someone in your audience (you just can’t predict to whom they will happen)
- dandare 9y ago> Most people believed that fat is converted to energy or heat, which violates the law of conservation of mass. We suspect this misconception is caused by the “energy in/energy out” mantra... I would not call it a misconception but simplification. Otherwise it is a very surprising article.
- dugluak 9y agoa kid asked me a similar question years ago - when you delete a file from the computer, where does it go?
- sampo 9y agoWell, at 37.7 MJ/kg energy content in fat and E=mc², 4.2 micrograms of the mass of that 10 kg does disappear.
- stillbourne 9y agohttps://www.youtube.com/watch?v=vuIlsN32WaE https://www.youtube.com/watch?v=vuIlsN32WaE
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- pessimizer 9y agoIsn't this the same question as "after you eat, where does the food go?" or "after you put gas in your gas tank, where does the gas go?"
- beefman 9y agoRelated is Feynman's comment on where trees come from: Most people think they grow out of the Earth, but they really grow out of the air.
- agumonkey 9y agoSomeone on youtube made a perfect video explaining this with enough precision: not sure it's this one https://www.youtube.com/watch?v=vuIlsN32WaE https://www.youtube.com/watch?v=vuIlsN32WaE but close
- compsciphd 9y agoI thought it just walked away. :)
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- heroku 9y agowhy do you guys put a bait title to insult me with your technical junks /:
- scottmcdot 9y agoAfter the reaction between adipose triglyceride and oxygen, do we wee out the water or sweat it out?
- agjacobson 9y agoOut your piss.