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eli5 Where does fat go when you lose it?

eli5 Where does fat go when you lose it?

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The_Thunder_Child

When your body uses its fat deposits as "fuel" it does so by breaking the chemical bonds in the fat molecules which releases energy. The byproducts of this are water and CO2. Water is removed from the body through urination and sweat. CO2 is removed from the body by breathing it out.


IlRaptoRIl

To add to that, of the weight you lose, 84% is lost as CO2 and only 16% is lost as water.


duksinarw

Breathing harder rn


sargassopearl

Me too.


duksinarw

r/loseit


ozzien20

Instructions unclear. Didn't lose weight by breathing.


Golden_Shadow64

You do infact lose weight by breathing. Why do you think you weight less in the morning? You don't drink or eat while asleep so no mass input, you don't do anything besides breath and maybe sweat on a warm night yet you wake up 2ish pounds lighter


Xygore

You'd lose more weight from the heat your body generates than the act of breathing itself. The body gets rid of the Co2 on your breath, but that's not how it's made.


dabman

Good clarification, but I think they’re referring to the breath as the “output” of mass, not necessarily the source. Most people think weight is lost either by fat turning into energy, or weight leaving the body as urine or fecal matter. Most people do not think the primary output of organic body mass is from gases exhaled from the lungs.


ihavemymaskon

are you saying that fat turns into energy? do you really believe your body is splitting atoms inside you?


mactofthefatter

Breaking chemical bonds doesn't mean splitting atoms.


ihavemymaskon

You'd lose more weight from the heat your body generates than the act of breathing itself" - please explain this. my chemistry teacher thought me that 'heat' is generated by reacting oxygen with fat, which comes from breathing in. heat is produced, you do not lose weight FROM the heat, you CREATE heat by losing weight.


Top-Copy248

This effect can only occur in your brown fat cells and reacting oxygen with fat is a huge oversimplification.


DustinDortch

Did you skip a ton of science between watching ice melt and nuclear reactions? Chemistry offers the answers.


ihavemymaskon

what??


DustinDortch

Fat is a mechanism to store energy. That energy must be converted, which starts with getting into a form that your body can use, so it travels to the liver where it is converted to ketones (mostly, some cells can use fat directly, and some fat will also be converted to glucose) that can be used similarly to ATP. These are then delivered to cells where they are use for energy by converting them into their constituent parts which is an exothermic chemical reaction (meaning the reaction releases energy). All of these stores of energy, be they glucose, protein, fat, or alcohol, are essentially a form of a hydrocarbon (or close thereto), which means their primary constituent parts of hydrogen and carbon. When we inhale oxygen (o2), this process splits the hydrogen and carbon from each other and bonds them with oxygen, resulting in h2o and co2. The h2o is processed out of the bloodstream by the kidneys filling the bladder and expelled through urination, and some h2o will also be excreted via sweat via the sweat glands. The co2 is processed out of the bloodstream by the lungs when we exhale. Ta da! EDIT: To your question of "what??", I am talking about this and all of the various forms of energy that we use in the world that are not based on nuclear reactions. When we burn materials to make heat, those are not nuclear reactions, but exothermic chemical reactions. Sometimes we use that heat to increase the temperature of water and drive a steam engine. Sometimes we use that heat to heat air and other components and drive a crankshaft. We have all sorts of different forms of energy that aren't nuclear: ​ * Kinetic * Chemical * Electrical * Potential Your statement leads one to see that you might not have an understanding of these concepts, which is odd if you understand something about nuclear energy because you would be skipping over a ton of science that is considered by many to be foundational.


panarypeanutbutter

The breakdown of fat is, like most reactions involving a molecule breaking down, one that releases energy. It is not atoms splitting, but molecules. I'm not sure where you got that bit from Your body is realistically, always undergoing this kind of reaction, sometimes using fat, sometimes other things, often in order to produce heat for your survival. This is why required caloric intake is greater at a higher temperature, and why you can lose weight by doing next to nothing at a cold temp - your body is putting energy into just keeping you warm.


ozzien20

JFC people. It's a joke! Laugh and move on. /r/woosh


WifeTookTheKids420

I thought jokes were funny


forworse2020

Umm, no, we won't move on? Valuable information being disseminated here...


CortexRex

Did all of you get wooshed or what? He made a joke and people tried to correct him, then he even replied said he was kidding and then you guys are still trying to correct him .


forworse2020

...Or what. It's a pretty standard formula joke; it was cute, sure, but advocating for it is a bit much. Only one person corrected him, the rest are just interested in the trivia from that correction. That's why the explanation is getting more attention than the "joke". It just happened to be more interesting. That's all. You're kind of making it worse for him by bringing attention to the fact that it didn't land. Could've ended where it did.


CortexRex

I'm bringing attention to the fact that a whole lot of redditors are oblivious and are the type of assholes that like to butt into conversations with "well actually..." Even when the person was obviously making a joke, with like you said a very very standard formula.


forworse2020

Ok. Again, it was one correction. People then responded to that singular correction with interest. Not sure if you can actually see that You want someone to acknowledge the joke? Ha - intructions unclear, that was a good one from your friend. Now are we allowed to be interested in the subject matter again?


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SietchJacurutu

This person probably doesn’t either, some people just observe that they look/feel lighter in the mornings, and also studies have been done to show this, which is probably the relatively common knowledge they were referencing. No need for snark.


mlwspace2005

Depends on how much you care about your weight. It's actually quite fascinating to observe how it fluctuates throughout the day when you consider it tells us a lot about how the human body functions.


GlazedDonutGloryHole

Biggest change in a single 24 hour period I've seen for myself has been 7 1/2 pounds after I started powerlifting again here recently.


felidae_tsk

You do, but it's slow process. In order to "burn" 1g of fat you have to breathe in 2.9g of oxygen and breathe out 2.8g of CO2. An average person breathe out 5-18 litres (2.5-9g) of CO2 per hour depending on the activity.


wernerbotha17

You forgot to pee.


ihavemymaskon

you need an oxygen demand, otherwise it's just hyperventilating.


aknutal

so you're saying we should all get super fat to act as the Amazon and store co2, like the obese trees we truly are?


lniko2

Save the planet, store CO2. I'm doing my part!


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Faschmizzle

Someone should start a combination gym/growroom so all the exhaled CO2 feeds the plants.


Eulers_ID

Fun fact: the CO2 losing weight process in reverse is how plants gain weight. Most of the mass of trees and plants comes from the CO2 they inhale.


Brainsonastick

Less fun fact: this is why old growth forests filled with trees that are mostly done growing are very nearly carbon neutral, rather than carbon negative like new growth. Not all trees fight global warming equally. That’s why it’s so important we keep planting new ones.


aurumae

I’m curious whether forests or grasslands are better carbon sinks over the long term. Forests like you point out eventually become carbon neutral, but I’ve seen some evidence that grasslands with grazing animals constantly turn plant matter into new soil and so might be better carbon sinks in the long run


mlwspace2005

Grazing animals are even worse for the environment than the carbon they are removing generally, by nature of their own gas emissions. The answer seems to be that you should plant forests and raze them ever feel decades /s


Muffinshire

Not even /s - there are plenty of plants whose seeds only germinate after a fire has razed the fully-grown ones to the ground. One of those circle of life things.


mlwspace2005

It is /s in this context lol, burning down a forest is counter productive when your goal is carbon capture lol


kutzyanutzoff

Exhaled CO² finds it's way to plants through winds already. Just open the windows of the gym. That is enough.


threebillion6

Yeah but money?


kutzyanutzoff

What money? Unless you have a huge (I mean huge, wider than whole blocks) gym and a small farm, the CO² volume difference is insignificant from the CO² you would get from opening the windows. Think it this way. If it would make any difference, farmers would burn animal shit in enclosed farms, effectively creating much more CO² than you would get from human breath.


threebillion6

It's a gimmick. Yoga/cycling/bonsai garden. Lol. I'm joking.


kutzyanutzoff

Alright. Have a nice day.


BlueBlooper

Cake day


kutzyanutzoff

Thanks.


sirdabs

C02 makes a huge difference. I use propane burners to raise c02 from ambient (550ppm) to 1250ppm for indoor gardening.


kutzyanutzoff

CO² does. But human breath sourced CO² is low in volume. That is the point I try to make. Propane burners and human breath can't be compared in this situation. And indoor gardening is not equal to large scale farming.


anoneesh

That's such an environmentally and economically horrible thing to do. Unless you're also using that to heat your house and getting some kinda dual use of that fuel.


autoantinatalist

I think they mean money from the AC. You open a window, you're burning money.


Infamous_Car_7829

when something releases water an carbon dioxide, that's combustion, r u telling me that people literally "burn fat"?


Kenail_Rintoon

Yes. You get water, carbon dioxide and heat. Sounds like a workout :)


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Theycallmelizardboy

What the hell does that have to do with anything and what are you even talking about?


Bivolion13

But... when does this happen? From what I know you don't lose fat unless you're at a caloric deficit. So on day 1 of being at a caloric deficit, does your body immediately start burning fat for fuel? Is there a distinct trigger or is it just an "always on" body feature that happens to burn fat faster than you make fat based on your caloric intake? Does it do this throughout the day or just when your body is most active? Is there a specific... smell or something that distinguishes regular breathing from expelling gross fat co2?


spottyPotty

Here's my understanding: Your body runs on glucose from carbs. Pumping too much glucose (glycogen?) too quickly into your blood stream, elevating your blood sugar level, is a dangerous condition, so your pancreas pumps out insulin, which is a signal for your cells to absorb the excess glucose by converting it into fat. (This reaction overcompensates and results in your blood sugar level being decreased too much which is why you feel sleepy after a carb-heavy meal). Your glycogen stores last around 24 hours. If you lower your daily net glucose consumption to 20g or less (more for some people), after your stores run out, your body will start producing ketones from the stored fat, turning it back into a useful energy source. You are said to be "in ketosis" when this happens. Your body becomes much more efficient at burning fat that you consume and that you have stored. This is the basis for the ketogenic diet or "keto". CO2 is a byproduct of the cellular metabolic reactions. This is carried back to your lungs by capillaries and veins. It's part of the same cardiovascular system of arteries and capillaries that carry oxygen from your lungs to your cells. Edit: when in ketosis, breath can smell a little more metallic


wobble_bot

Your body will always initially burn fuel from carbohydrates, as it’s the easiest to access. You can store some, but not a lot, which is why you might find yourself having immense sugar crashes if you eat something like cereal for breakfast. Your body will then look to proteins or fats to convert to energy. You don’t have to be in a calories deficit to burn fat. Diets, such as the Keto cut carbs drastically to force the body to utilise fats as fuel


Bivolion13

...Wait I don't think using fats as fuel is the same as burning actual bodily fat deposits is it? I thought this question was asking about actually burning love handles


3_Thumbs_Up

>...Wait I don't think using fats as fuel is the same as burning actual bodily fat deposits is it? Why would the difference be?


Bivolion13

Well if you eat 100g of bacon that's 42g of fat. That doesn't mean the pork fat is deposited into your body and you need to burn the 42g. It's fat as a nutrient vs literal body fat.


Tuberoinfundibular

The fat from food gets stored in your body as literal body fat. Its just that the body prefers to burn carbohydrates and will only burn fat if there's really low glucose. Fat is excellence storage because you can generate considerably more ATP from a typical fatty acid molecule by breaking its bonds compared to the storage form of glucose (glycogen). In short, dietary fat and body fat are very similar, and the process of using either as fuel is pretty much the same.


xavierash

If my body is burning fat and proteins once my carb stores deplete, how does it decide between burning off the spare tyre which I want, and breaking down muscle which I absolutely do not? Is there a way to nudge it one way or the other?


Tuberoinfundibular

I'm pretty sure that the body will prefer to burn fat over proteins - you will only begin to burn proteins once your fat stores run out or get very low.


yayforfood1

u prevent muscle breakdown through exercise


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Bivolion13

... that's what I said to the above poster.


Kenail_Rintoon

You're right, I failed at reading. Removed my post.


AquaRegia

>Diets, such as the Keto cut carbs drastically to force the body to utilise fats as fuel Yes, but you don't replace the carbs in your diet with nothing, you replace them with fat. So instead of burning 10 units of fat and eating 10 units of fat, you burn 20 units of fat and eat 20 units of fat.


wobble_bot

Absolutely, however fats and protein do release the ‘I’m full’ hormone quicker than carbs, leading to less snacking, smaller portions and so on


AloneIntheCorner

The difference is instead of eating 10 units of *carbs* and burning 10 units of carbs, you're eating 10 units of fat and burning 10 units of fat. Despite the names, carbs store as weight much easier than fats, and they burn before body fat does. So if you're trying to lose weight, every carb you cut is body fat being burnt (assuming caloric deficit of course).


AquaRegia

Fat is the primary fuel\*, and carbs only get involved when the energy needed (per second) is higher than what fat oxidation can provide (per second). And assuming a caloric deficit, every calorie you cut is body fat being burnt, doesn't matter if it's from carbs, fat, protein or alcohol. ​ >\*The respiratory exchange ratio (RER) is the ratio between the amount of carbon dioxide (CO2) produced in metabolism and oxygen (O2) used.\[1\]\[2\] > >The ratio is determined by comparing exhaled gases to room air. Measuring this ratio can be used for estimating the respiratory quotient (RQ), **an indicator of which fuel (e.g. carbohydrate or fat) is being metabolized** to supply the body with energy. > >An RER near 0.7 indicates that fat is the predominant fuel source, a value of 1.0 is indicative of carbohydrate being the predominant fuel source, and a value between 0.7 and 1.0 suggests a mix of both fat and carbohydrate.\[4\] In general a mixed diet corresponds with an RER of approximately 0.8. [https://en.wikipedia.org/wiki/Respiratory\_exchange\_ratio](https://en.wikipedia.org/wiki/Respiratory_exchange_ratio)


AquaRegia

You're *always* using fat for fuel, 24/7. It just gets replenished all the time, either less or more than the amount you use, depending on your caloric intake.


Paltenburg

>From what I know you don't lose fat unless you're at a caloric deficit. I mean you loose fat all the time, it's just that a lot of people eat so much that they gain fat faster than that they loose it.


Phattd

I'm not sure I follow how the CO2 from fat in your thighs gets to your lungs for you to exhale? Would it travel in your blood stream?


nancylyn

Yes


Phattd

That's weird.


jlharper

I don't mean this in a rude way, but what do you think of blood as being for, if not for transporting the various chemicals the body consumes and creates to the position in the body where they are needed?


Theycallmelizardboy

I thought it was just some red stuff that was good to paint nurseries with....


Phattd

It's weird that it would flow through the body as a liquid and the turn into a gas that you could exhale.


jlharper

It flows in the liquid, but as a gas. Blood is a liquid medium which is capable of carrying solids, liquids and gasses.


nancylyn

What is?


Tuberoinfundibular

Fat can be broken down into CO2 and water within any cell. When CO2 is formed, it enters the bloodstream via capillaries - tiny blood vessels that are close to all of our cells. In the blood, CO2 travels in the form of bicarbonate since it reacts with water in our blood - bicarbonate then travels to the lungs where a reaction occurs that expels CO2. The body is a really weird and amazing machine.


azzyx

Yes, it does so in different ways, but all of them through the blood stream. You can read more about it [here](https://courses.lumenlearning.com/wm-biology2/chapter/transport-of-carbon-dioxide-in-the-blood/).


abearhasnoname

For fun try weighing yourself before and after running. Even without peeing I have noticed changes of 1 to 2 pounds.


Tinchotesk

But how do you control for water loss through sweat?


BBHBHBHBB

EZ, run in a suit made of plastic bags.


AloneIntheCorner

You don't. Water is a product of burning sugars, losing water is part of losing weight.


403Verboten

A better test would be to weigh yourself before going to bed and again when you wake up. Unless you sweat balls all night it'd be a lot easier to control for water loss.


TScottFitzgerald

I generally stay low carb but without any hard rules, so some days I only eat fruits and veggies and on others I might go full out pizza or pasta, and my water weight fluctuates ridiculously, I might have a 5kg difference within two days. Definitely made me realise how BS BMI and other calculators that only consider body weight can be, unless you also correct for body fat and composition.


wskyindjar

I was always a steady .4 lbs per mile run (until I started having to eat and drink 10 miles or more)


Oscribble

This might be a dumb question but is this why we lose weight when exercising? The increased breathing and sweat? Or is the actual act of exercising doing something to reduce fat?


jlharper

Exercise requires energy. Animals gain energy from food, and store excessive energy as fat. First your body will burn the food you've eaten recently by breaking it down into sugar, and using that sugar as fuel for your cells. The sugar is turned into a chemical called ATP, and that is the fuel our cells use. Once that is all gone then the body will turn to the secondary energy reserve, the fat deposits. Animal fat can also be turned into ATP, and so when it is broken down it can be used in place of sugars to fuel cells.


Oscribble

Thanks for the reply, very interesting! :)


jlharper

No problem, it's a good question and one that a lot of people don't really consider. These are the kind of questions that show you're thinking about the actual mechanics of the process and that's really the furthest thing from dumb.


The_Thunder_Child

No, because your body would be using your fat stores for energy.


Paltenburg

I think he means right after the exercising.. fat burning doesn't happen that quickly, by then it's probably a difference in moisture.


btribble

Don't forget urea. Urea is another "byproduct".


Hampsterman82

No that's from protein metabolism. They were discussing like if only fat was metabolized unlike a normal body where at least a bit of everything is throughout the day.


btribble

Adipose tissue produces urea as part of its own amino acid synthesis and regulation, but if we set aside basic cell function and are just talking about the burning of "fat calories" then... *sure*?


gaurjimmy

>CO2 is removed from the body by breathing it out. Via the ass. In my case, at least.


JsDaFax

There’s an excellent Ted Talk on [this](https://youtu.be/vuIlsN32WaE).


Vishwas3190

Are you referring to the below equation? C55H104O6+78O2 --> 55CO2+52H2O+energy.


SYLOH

When they say "burning fat", from a chemistry standpoint, they're being quite literal. The fat is a fuel for your metabolism. You breathe in oxygen. The fat then burns into carbon dioxide, water and some other waste products. You then breathe out the carbon dioxide. The weight of your exhalation is higher than your inhalation. You are getting lighter one breath at a time.


Koooooj

The fat itself is large molecules with lots and lots of carbon and hydrogen. This is stored inside of fat cells. When you burn that fat your body combines those molecules with oxygen. The carbon winds up as CO2 (carbon dioxide), while the hydrogen winds up as H20 (water). The CO2 is exhaled, while the water has numerous means of leaving your body, most notably sweat, urine, and moisture in your lungs/throat. The hydrogen atoms are much more numerous than carbon, but the carbon are much heavier so they make up the majority of the weight you lose. To lose more fat a strategy would be to breathe more, but to do that without hyperventilating you want to have a use for all that oxygen. A sustained physical exertion will do that. This is just a roundabout way of arriving at the obvious conclusion that cardio exercise will help with losing weight (note however that people already breathe a lot, so raising that amount significantly takes a lot of cardio. It's often easier to just eat less and let your normal breathing evict carbon molecules from your body). The fat cells themselves generally stick around, but they're smaller since they have less fat in them. They may die and be disposed of by your immune system, kidneys, etc, ultimately leaving through your urine. Liposuction takes the direct approach here and just removes them from your body directly.


Insomnia6033

Yeah, my understanding was when you lose weight you don't actually lose fat cells, they just get smaller, the actual number of them stays the same. People who get liposuction will sometimes get fat in weird places, since the cells that would typically expand due to a weight increase are now no longer there so the fat cells in other parts of the body will then expand instead. edit: spelling


GrizzKarizz

I remember reading/hearing once that once a fat cell has been made, it stays with the person forever, which in turn makes it easier to someone to regain the weight, hence it's best to not gain weight in the first place. Is there any truth to this?


IvyTh3Twisted

According to my A&P college professor who is a MD, what you’ve wrote is accurate.


Vishwas3190

Does this mean there is no way to reduce number of fat cells through exercise and diet? Until of course age catches up


GrizzKarizz

I'm a layman, please don't take this as fact, but that's my understanding. I guess, it's just best to ensure you don't make more fat cells.


xavierash

Apart from storing energy in the form of fat, is there any other bodily function provided by the fat stores? If liposuction is physically removing fat cells, what's to stop someone removing the whole layer of adipose tissue? Does it grow back?


Living-Complex-1368

Interesingly, a few techniques that replace liposuction are based on just killing the fat cells and letting the immune system get rid of the dead cells. One of the techniques was actually the fitst step of liposuction, before the actual cutting and suction.


Holgrin

Mostly exhalation. You generally breathe it out. There is excrement (poo) and urination (pee) and sweat that passes a lot of liquid and solids out of your body, but stored fat doesn't move back into your digestive tract to leave through the anus or urethra (butt or front genitalia). Fat is broken down and, at least partially, exhaled through your breath. Probably small numbers of molecules are passed through sweat, but most of the actual "weight" (or mass) is exhaled.


si2141

Like most people said you breathe it out, now don't force yourself to breathe heavily to get that summer body you will hyperventilate and harm your body.


bigbaltic

Fat cells don't go anywhere. You exhale out CO2 and pee out water, but the cells don't go anywhere.


Paltenburg

The fat molecules do though


bigbaltic

Water and carbon inside the far cell, sure


ransua17

Fat gets turned into energy. Fat is like the gas tank on your car, but if you use less gas then you put in then your car is always full. In animals and people that becomes fat. But just like when you run your car, that gas gets burned and turned into energy that runs the engine, the fat gets burned and turned into energy as well. In the case of fat (and the human/animal body) the engine is a part of all your cells called the mitochondria. The mitochondria takes the long chains of hydrocarbons and combines it with oxygen to create carbondioxide and water. When those carbon molecules break they release energy. It gets more complicated than that but that is the just of it.


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Phage0070

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si2141

your fart is now one with the nature!


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kynthrus

I was wondering this the other day. I've been working out recently and I'll go to bed weighing 90kilo and wake up weighing 89.3 kilos. where is that .7 kilograms going?


The_Thunder_Child

Most of that would be water lost through breathing (the whole you fog up a mirror when you breathe on it thing) or sweating.


Hefty_Exchange_2044

agree, it turns out to sweat.


avo888

[This video](https://www.youtube.com/watch?v=lL2e0rWvjKI) from Veritasium explains this pretty well.


Minnentonka

Theres a ted talk about this and believe it or not it turns into air..we'll Carbondioxide to be exact


B-the-Excellent

We use it as organic fuel as we burn calories. Think of fat as a sort of gasoline that we store as 100%+++ and insteqd of just running out of fuel we just add on the pounds. Fat really just translates as stored energy/potential waiting for the worst of times. When we use fat, in nature, is when resources are scarce and we store extra calories, or food energy, as fat.


B-the-Excellent

Drunk me meant that during scarce times we use the fat as stored energy and times of abundance we store excess energy as fat


7h4tguy

People are primarily oxygen and carbon. Exactly the chemical reaction for fire. Digestion is also oxidation (slow burning fire). We are stars (H-He, CNO), basically.


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Phage0070

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buried_treasure

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Ricksterdinium

So to keep gains i should stop breathing?


qyi000

Fat is just a way of energy storage , if i'M not mistaken it's 99.5% efficient, and therefore its actually most efficient way of storing energy in our body. When you burn fat - it's actually exactly as it's called. Energy is used to fulfill extra effort during for example prolonged exercise . Some of it comes from fat, for professional maraton runners it's around 50% , rest comes from energy stored around muscles.


Bluemousey111

I thought we keep our fat cells until we die or have them surgically (lipo) or accidentally (wound, dismemberment). They just increase in size and number and as body fat increases. So its the content of the fat cell that is lost and not the cell, correct?


chamillion03

Long story short, blood. Eventually your heart will process the fat deposits out of your blood system.


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buried_treasure

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ransua17

Fat gets turned into energy. Fat is like the gas tank on your car, but if you use less gas then you put in then your car is always full. In animals and people that becomes fat. But just like when you run your car, that gas gets burned and turned into energy that runs the engine, the fat gets burned and turned into energy as well. In the case of fat (and the human/animal body) the engine is a part of all your cells called the mitochondria. The mitochondria takes the long chains of hydrocarbons and combines it with oxygen to create carbondioxide and water. When those carbon molecules break they release energy. It gets more complicated than that but that is the just of it.