Biochemistry answers to weight loss questions: Where does the weight go?

Aaron_K123
Aaron_K123 Posts: 7,122 Member
edited May 2023 in Health and Weight Loss
I see this question on the thread a lot:

"Okay I get that if I eat less calories than I use I will lose weight, but where does that weight actually go?"

The assumption seems to be that you either poop it out somehow or that you literally convert mass into energy like you were some sort of nuclear reactor. Neither one of these is correct. The answer comes from biochemistry and I thought I'd try to give a layman explanation of what is going on when you eat food and do work. By explaining that it becomes evident where the weight goes.

First lets address the idea that you lose weight by essentially pooping it out. When you eat food enters your mouth and goes through your gastrointestinal tract. That is basically a tube from your mouth to your *kitten* that, if you think about it, is actually "outside" of your body. The parts you can digest are broken down into smaller soluble pieces and transferred through your intestinal wall to your blood. What remains behind just passes through you and as such was never really inside you in the first place. Nothing substantial crosses that lining in the opposite direction so what you poop out is just what you couldn't digest mixed with the bacteria that are in your gut. The weight you lose from pooping is just whatever you ate that you couldn't digest mixed with bacteria that is in your gut, it is not weight that was ever a part of you. Therefore you do not lose weight from your body through excrement.

The next idea is that you convert fat into energy and fat has mass and energy doesn't so you are literally just destroying mass inside of you. The more fat you convert the more weight you lose as a result. That doesn't happen. We do breakdown fats and other biomolecules to get energy but the mass is conserved, you are just breaking it down into parts that weigh the same amount as the whole. The only thing that converts mass to energy is a nuclear reaction and our bodies aren't nuclear reactors. Our body temperature is about 37 degrees celsius, not the 100 million degrees nuclear fusion would require. Therefore you don't lose weight from conversion of mass to energy.

So how do we lose weight? Well to understand that we have to look at how we do convert the food we eat into usable energy. The food we eat has one thing in common, the part that gives us sustenance in the form of calories are molecules comprised of carbon (C), hydrogen (H) and oxygen (O). Fats, or hydrocarbons, are made of just C and H. Protein is made from units called amino acids that are composed of carbon, hydrogen, oxygen and nitrogen. Carbohydrates are carbon, C, combined with water, H20, to form a carbo-hydrate CxH2x0x. Glucose for example is C6H12O6 which is essentially 6 carbons and 6 waters. Molecules that are based around carbon as these are are referred to as organic molecules.

When you eat pasta your GI tract breaks down the starches into their constitutive soluble parts which are glucose molecules. Those molecules then transfer across your intestinal lining to your blood raising your blood sugar which triggers insulin which triggers your cells to uptake glucose. Glucose is then broken down by a long series of enzymatic reactions which are oxidative, they use oxygen to break bonds in the molecule. When a chemical bond is broken some energy is released and these enzymes capture that release of energy by forming of a new bond in a "currency" molecule converting adenosine diphosphate into adenosine triphosphate (ATP). ATP is used almost like a battery for universal energy storage. Other processes in our body can be powered by these batteries which allows the production of ATP to essentially power our bodies by breaking the bond in ATP to form ADP which can then be converted back to ATP by the breakdown of bonds in food molecules.

Most of that energy capture and coupling happens through the electron transport chain (ETC) which is too complex to cover in a thread and would confuse/bore the hell out of people as I spent pages and pages trying to explain. I guess the analogy for the ETC would be picture a society where energy from lots of different specialized sources is used to transport water uphill and when that water flows back down through a channel it flows through a water-wheel that turns a turbine that produces energy that is put into rechargable batteries that are usable by everyone. In this analogy the water is protons and the energy input is food while the rechargable batteries are ATP molecules.

For those who are curious here is the ETC "water wheel" ATP synthase in action. https://www.youtube.com/watch?v=b_cp8MsnZFA

So what does that end up looking like in total? What happens to that glucose molecule?

Well glucose, C6H12O6 is broken apart by oxygen, O2, to smaller water and carbon dioxide molecules with the released energy captured in ATP molecules with some waste energy released as heat.

C6H12O6 + 6 O2 + 32 ADP >>>> 6 C02 + 6 H20 + 32 ATP + heat

So when we say that we "burn" calories it is just a phrase but it is a surprisingly accurate one. Burning something is also an oxidation reaction, which is why fire requires oxygen. If you literally burn glucose by setting it on fire then the reaction that is occuring is:

C6H12O6 + 6 O2 >>>> 6 C02 + 6 H20 + heat.

The only difference between this and what happens in your body is that in your body the reaction is carried out by enzymes that capture most of that energy in the form of bonds in ATP while in a fire that energy is entirely converted into heat.

So lets track the mass here. ADP >>> ATP is cyclical, the ADP and ATP stay in your body its just a way of storing energy so that isn't it. Water is kept in balance in your body, sure you excrete water in the form of urine, sweat, tears, etc but you also need to drink water to keep hydrated and keep your water levels the same so that isn't it. You breath in oxygen to carry out these oxidative reactions and you breath out carbon dioxide as a waste product. That isn't balanced, carbon dioxide is essentially oxygen plus carbon. So if you breath in 6 oxygen molecules and breath out 6 carbon dioxide molecules you have essentially lost 6 carbons from your body.

Now if all you do is burn the glucose you eat for energy then that carbon comes from the glucose you ate so you would not lose any weight (the C you breath out is balanced by the C you just ate). However if you take in less calories than you need to power your body you will break down glycogen (stored glucose) and/or fats (stored hydrocarbons) within your body by oxidizing them from breathed in oxygen and then breath out carbon dioxide. As a result, you lose weight. If, however, you eat more calorically than your body requires for energy your body will store the excess in the form of either glycogen (for glucose) or triglycerides (for fats) and since those molecules have weight you will gain weight. Although I used glucose as the example here the sample principle would hold true of fats as well. Proteins also contain nitrogen and waste nitrogen is excreted in the form of uric acid in our urine.

So what is the answer? When you lose weight the weight you are losing is being breathed out in the form of carbon in carbon dioxide. The amount of carbon dioxide you breath out is connected to how metabolically active you are which in turn is connected to how physically active you are being. If you go for a run you will breakdown molecules to create energy which will require more oxygen and expel more carbon dioxide which is why you have to breath harder. If, instead, you just sit on your couch and breath hard you are taking more breaths but you aren't actually producing more carbon dioxide all you are doing is expelling less carbon dioxide per exhale...that is just hyperventilating and won't do anything other than making you a bit light headed.




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Replies

  • AnvilHead
    AnvilHead Posts: 18,343 Member
    Thank you for taking the time to post threads like this, Aaron. Very interesting and educational.
  • etherealanwar
    etherealanwar Posts: 465 Member
    Very insightful, thanks for the information!!
  • anubis609
    anubis609 Posts: 3,966 Member
    Dude, thank you for this. It's refreshing to see biochemistry, as much as others get turned off by it, I appreciate the hell out of it.
  • snowflake954
    snowflake954 Posts: 8,399 Member
    Aaron--love your explanations. Thanks for taking the time to educate. I can say I learned something today.
  • Mikkimeow
    Mikkimeow Posts: 139 Member
    Thank you!!!! This is very interesting. I know this has been highly requested!
  • Tacklewasher
    Tacklewasher Posts: 7,122 Member
    Doesn't some of it get expelled as water? I thought the breakdown was 86% CO2 and 14% H2O, some of which would be expelled.

    I'm thinking as my weight drops, I'm carrying less water than before.
  • jjpptt2
    jjpptt2 Posts: 5,650 Member
    Is there a Biochemistry answers to weight loss questions for dummies thread somewhere???

    I'm kidding. Kind of. Good posts though, thank you.
  • lightenup2016
    lightenup2016 Posts: 1,055 Member
    edited March 2018
    Aaron_K123 wrote: »
    So if I'm breathing out my weight that I'm losing, does that mean my kids are breathing me in as they're growing? :lol:

    Kids no, houseplants yes.

    Plants run this reaction in the other direction. Plants take in and combine CO2 with H20 using energy from the sun to form glucose which they keep and oxygen which they expel. Animals take in oxygen and food to break down molecules like glucose to produce energy as well as form H20 and CO2 which they expel.

    Therefore a plants mass comes from the carbon from CO2, and if you are expelling that CO2 then yes, they would be incorporating "your" carbon into their "bodies". Only way carbon that is in you ends up in your kid is if you breath out around a fruit tree and later your kids eat the fruit. Circle of life and all.

    Right, I realized this after I posted it. Still funny, though, to think that my family is breathing in my breath that contains the carbon dioxide from the pounds I lost. We only have one house plant, but it doesn't seem to be benefiting much!
  • solieco1
    solieco1 Posts: 1,559 Member
    So if I'm breathing out my weight that I'm losing, does that mean my kids are breathing me in as they're growing? :lol:

    My kids grow like houseplants......hmmmmm....:)
  • 1houndgal
    1houndgal Posts: 558 Member
    Aaron_K123 wrote: »
    I see this question on the thread a lot:

    "Okay I get that if I eat less calories than I use I will lose weight, but where does that weight actually go?"

    The assumption seems to be that you either poop it out somehow or that you literally convert mass into energy like you were some sort of nuclear reactor. Neither one of these is correct. The answer comes from biochemistry and I thought I'd try to give a layman explanation of what is going on when you eat food and do work. By explaining that it becomes evident where the weight goes.

    First lets address the idea that you lose weight by essentially pooping it out. When you eat food enters your mouth and goes through your gastrointestinal tract. That is basically a tube from your mouth to your *kitten* that, if you think about it, is actually "outside" of your body. The parts you can digest are broken down into smaller soluble pieces and transferred through your intestinal wall to your blood. What remains behind just passes through you and as such was never really inside you in the first place. Nothing substantial crosses that lining in the opposite direction so what you poop out is just what you couldn't digest mixed with the bacteria that are in your gut. The weight you lose from pooping is just whatever you ate that you couldn't digest mixed with bacteria that is in your gut, it is not weight that was ever a part of you. Therefore you do not lose weight from your body through excrement.

    The next idea is that you convert fat into energy and fat has mass and energy doesn't so you are literally just destroying mass inside of you. The more fat you convert the more weight you lose as a result. That doesn't happen. We do breakdown fats and other biomolecules to get energy but the mass is conserved, you are just breaking it down into parts that weigh the same amount as the whole. The only thing that converts mass to energy is a nuclear reaction and our bodies aren't nuclear reactors. Our body temperature is about 37 degrees celsius, not the 100 million degrees nuclear fusion would require. Therefore you don't lose weight from conversion of mass to energy.

    So how do we lose weight? Well to understand that we have to look at how we do convert the food we eat into usable energy. The food we eat has one thing in common, the part that gives us sustenance in the form of calories are molecules comprised of carbon (C), hydrogen (H) and oxygen (O). Fats, or hydrocarbons, are made of just C and H. Protein is made from units called amino acids that are composed of carbon, hydrogen, oxygen and nitrogen. Carbohydrates are carbon, C, combined with water, H20, to form a carbo-hydrate CxH2x0x. Glucose for example is C6H12O6 which is essentially 6 carbons and 6 waters. Molecules that are based around carbon as these are are referred to as organic molecules.

    When you eat pasta your GI tract breaks down the starches into their constitutive soluble parts which are glucose molecules. Those molecules then transfer across your intestinal lining to your blood raising your blood sugar which triggers insulin which triggers your cells to uptake glucose. Glucose is then broken down by a long series of enzymatic reactions which are oxidative, they use oxygen to break bonds in the molecule. When a chemical bond is broken some energy is released and these enzymes capture that release of energy by forming of a new bond in a "currency" molecule converting adenosine diphosphate into adenosine triphosphate (ATP). ATP is used almost like a battery for universal energy storage. Other processes in our body can be powered by these batteries which allows the production of ATP to essentially power our bodies by breaking the bond in ATP to form ADP which can then be converted back to ATP by the breakdown of bonds in food molecules.

    Most of that energy capture and coupling happens through the electron transport chain (ETC) which is too complex to cover in a thread and would confuse/bore the hell out of people as I spent pages and pages trying to explain. I guess the analogy for the ETC would be picture a society where energy from lots of different specialized sources is used to transport water uphill and when that water flows back down through a channel it flows through a water-wheel that turns a turbine that produces energy that is put into rechargable batteries that are usable by everyone. In this analogy the water is protons and the energy input is food while the rechargable batteries are ATP molecules.

    For those who are curious here is the ETC "water wheel" ATP synthase in action. https://www.youtube.com/watch?v=b_cp8MsnZFA

    So what does that end up looking like in total? What happens to that glucose molecule?

    Well glucose, C6H12O6 is broken apart by oxygen, O2, to smaller water and carbon dioxide molecules with the released energy captured in ATP molecules with some waste energy released as heat.

    C6H12O6 + 6 O2 + 32 ADP >>>> 6 C02 + 6 H20 + 32 ATP + heat

    So when we say that we "burn" calories it is just a phrase but it is a surprisingly accurate one. Burning something is also an oxidation reaction, which is why fire requires oxygen. If you literally burn glucose by setting it on fire then the reaction that is occuring is:

    C6H12O6 + 6 O2 >>>> 6 C02 + 6 H20 + heat.

    The only difference between this and what happens in your body is that in your body the reaction is carried out by enzymes that capture most of that energy in the form of bonds in ATP while in a fire that energy is entirely converted into heat.

    So lets track the mass here. ADP >>> ATP is cyclical, the ADP and ATP stay in your body its just a way of storing energy so that isn't it. Water is kept in balance in your body, sure you excrete water in the form of urine, sweat, tears, etc but you also need to drink water to keep hydrated and keep your water levels the same so that isn't it. You breath in oxygen to carry out these oxidative reactions and you breath out carbon dioxide as a waste product. That isn't balanced, carbon dioxide is essentially oxygen plus carbon. So if you breath in 6 oxygen molecules and breath out 6 carbon dioxide molecules you have essentially lost 6 carbons from your body.

    Now if all you do is burn the glucose you eat for energy then that carbon comes from the glucose you ate so you would not lose any weight (the C you breath out is balanced by the C you just ate). However if you take in less calories than you need to power your body you will break down glycogen (stored glucose) and/or fats (stored hydrocarbons) within your body by oxidizing them from breathed in oxygen and then breath out carbon dioxide. As a result, you lose weight. If, however, you eat more calorically than your body requires for energy your body will store the excess in the form of either glycogen (for glucose) or triglycerides (for fats) and since those molecules have weight you will gain weight. Although I used glucose as the example here the sample principle would hold true of fats as well. Proteins also contain nitrogen and waste nitrogen is excreted in the form of uric acid in our urine.

    So what is the answer? When you lose weight the weight you are losing is being breathed out in the form of carbon in carbon dioxide. The amount of carbon dioxide you breath out is connected to how metabolically active you are which in turn is connected to how physically active you are being. If you go for a run you will breakdown molecules to create energy which will require more oxygen and expel more carbon dioxide which is why you have to breath harder. If, instead, you just sit on your couch and breath hard you are taking more breaths but you aren't actually producing more carbon dioxide all you are doing is expelling less carbon dioxide per exhale...that is just hyperventilating and won't do anything other than making you a bit light headed.




    You could write a biochemistry textbook. Wow!
  • 1houndgal
    1houndgal Posts: 558 Member
    You need more paragraphs though. Lol
  • aeloine
    aeloine Posts: 2,163 Member
    TL;DR: you breathe it out!

    That's SO badass.