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When we lose weight, where does it go?

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Re: When we lose weight, where does it go?

#61

Post by thaumasiotes »

mikepurvis wrote: post #47
habeebtc wrote: post #19

Earlier quoted context omitted.

I recall from Chemistry: When hydrocarbons combust, the outputs generally are CO2 and Water. Driven home by living with a gearhead after college. At least some of the liquid dripping from tailpipes is water.

Also relevant if you've ever looked into what a modern "condensing" boiler/furnace is: https://www.ernstheating.com/blog/condensing-furnaces/ A consequence of the secondary heat exchanger is that a bunch of the steam from the exhaust condenses back into water, and unfortunately it's water containing a bunch of heavy metals and other nasty stuff, which usually ends up flushed into the municipal sanitary sewer. Probabl…

> unfortunately it's water containing a bunch of heavy metals and other nasty stuff, which usually ends up flushed into the municipal sanitary sewer. Probably still better than it going up the chimney and into the atmosphere, but it would be nice if there was a way to capture and isolate those pollutants in that relatively concentrated state, before they end up mixed in with everyone's bathtub water.

You can't be claiming that your bathtub draws from untreated sewage? The treatment plant is a logical place to extract heavy metals and other nasty things; that is its entire purpose.

Re: When we lose weight, where does it go?

#62

Post by divbzero »

adatavizguy wrote: post #38

Likewise, where does that tree in your backyard come from? It is the product of carbon dioxide and water. edit: The significance of this thought is when a child is asked where a tree or plant comes from, at least in the US, they inevitably answer the ground when the answer should be rain that falls from the sky and air. With the naive notion a tree comes from the ground we miss the obvious which is the ground doesn't…

It’s really cool to observe, e.g. placing white stems of scallions in water and seeing green leaves materialize within days. The underlying biochemistry is fascinating too. [1]

[1]: https://en.wikipedia.org/wiki/RuBisCO

Re: When we lose weight, where does it go?

#63

Post by Retric »

thaumasiotes wrote: post #40
cperciva wrote: post #25

Earlier quoted context omitted.

I'd say water and CO2 and urea. Protein is roughly 16% Nitrogen by weight.

I was about to say, excreting water and CO2 leaves you no way at all to get rid of nitrogen.

Body fat is just a mix of HCO https://en.wikipedia.org/wiki/Fat

With extreme weight loss blood, protean, and even bone mass is included. So it’s really Oxygen, Carbon Hydrogen, Nitrogen, Calcium, Phosphorus, Potassium, Sulfur, Sodium, Chlorine, and Magnesium plus some trace elements. However, the body heavily favors removing water and fat with mild weight loss.

Re: When we lose weight, where does it go?

#64

Post by computerphage »

philwelch wrote: post #27
computerphage wrote: post #14

Earlier quoted context omitted.

In what way is it not true? When a reaction does convert mass to energy we call it a nuclear reaction

This is kind of pedantic, but to my understanding, even normal exothermic chemical reactions do convert mass to energy. It’s just that the amount of mass lost is extremely negligible. Conservation of mass is an oversimplification that is close enough to match any real world measurement you’d care about. Nuclear reactions are when you start getting into doing mass-energy conversion at scale.

Thank you. I didn't know that.

Re: When we lose weight, where does it go?

#65

Post by Joeri »

adatavizguy wrote: post #38

Likewise, where does that tree in your backyard come from? It is the product of carbon dioxide and water. edit: The significance of this thought is when a child is asked where a tree or plant comes from, at least in the US, they inevitably answer the ground when the answer should be rain that falls from the sky and air. With the naive notion a tree comes from the ground we miss the obvious which is the ground doesn't…

I never though about a tree that way, thank you for mentioning this.

I found this page explaining the process: https://serc.carleton.edu/eslabs/carbon/1a.html

Re: When we lose weight, where does it go?

#66

Post by evanb »

astrophysician wrote: post #4

> The most common misconception by far, was that fat is converted to energy. The problem with this theory is that it violates the law of conservation of matter, which all chemical reactions obey. I mean what they're getting at must be true, we are obviously not converting 1kg of rest mass into energy but that sentence is very much not true.

Chemical bonds are on the scale of eV---the cost to liberate an electron from a hydrogen atom is 13.6eV, for example. So the best you can hope for, in a chemical reaction, is a change in mass of the scale of 10s of eV / c^2.

In comparison, a single proton weighs 938 MeV = 9.38e+8 eV. So the fraction of the mass that is converted into energy is on the scale of 1e-7.

Re: When we lose weight, where does it go?

#67

Post by abhayhegde »

hprotagonist wrote: post #5

https://www.bmj.com/content/349/bmj.g7257 Meerman, R., & Brown, A. J. (2014). When somebody loses weight, where does the fat go? BMJ, 349(dec16 13), g7257–g7257. https://doi.org/10.1136/bmj.g7257 >Our calculations show that the lungs are the primary excretory organ for fat.

Thanks for backing it all up with a published article.

Re: When we lose weight, where does it go?

#69

Post by TheOtherHobbes »

astrophysician wrote: post #4

> The most common misconception by far, was that fat is converted to energy. The problem with this theory is that it violates the law of conservation of matter, which all chemical reactions obey. I mean what they're getting at must be true, we are obviously not converting 1kg of rest mass into energy but that sentence is very much not true.

There's no such thing as "conservation of matter." There's conservation of mass in basic chemistry, but it's really just a partial understanding of conservation of energy anyway.

It's almost as if the author has never heard of exothermic chemical reactions.

Re: When we lose weight, where does it go?

#70

Post by [deleted] »

tamcap wrote: post #48

The story is (likely purposefully) ignoring some other ways you can "lose weight/energy" from your body. But I am curious what would the complete list be... * heat (the most obvious one, not explicitly mentioned I guess?) * even in healthy humans, some fatty acids are excreted with bile into the gut and subsequently removed via feces * if you are fasting (or in ketosis, such as via keto diet) you will exhale / sweat…

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