When we lose weight, where does it go? • Hacker News Board

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

#71

Post by monkeybutton » Fri, Oct 02, 2020, 10:12 PM UTC

Joeri wrote: post #65

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

Neither did until I saw the clip in this article

>"People look at a tree and think it comes out of the ground, that plants grow out of the ground, " he says, but "if you ask, where does the substance [of the tree] come from? You find out ... trees come out of the air!"

https://www.npr.org/sections/krulwich/2012/09/25/161753383/t...

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

#72

Post by adatavizguy » Fri, Oct 02, 2020, 10:13 PM UTC

Joeri wrote: post #65

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

How did the farmer get his donkey out of the deep ditch? He filled it in with dirt. This is just Aesop's fable. But it falls into the same abstract thinking as where does fat go, C55H104O6+78O2 --> 55CO2+52H2O+energy[0], or what happens to a tree when it burns, CH4+4O2→CO2+H2O (plus heat!)[0]. We have a hard time seeing air (sic) as something tangible. Also, this inability to visualize abstract concepts leads to political points of view such as whether or not aerosol of breath contains disease or invisible gases causes global warming.

[0] Grabbed from first search results.

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

#73

Post by AtlasBarfed » Fri, Oct 02, 2020, 10:13 PM UTC

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.

Blog complaining scientists don't know physics and chemistry...

... doesn't know physics and chemistry.

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

#74

Post by Fezzik » Fri, Oct 02, 2020, 10:23 PM UTC

LolWolf wrote: post #2

Water and CO2? (And, of course, some other byproducts, but by and large.) I mean, I think this is a well-known answer, no? Sorry I don't mean to sound facetious, I haven't opened the article, so I may be surprised, but I thought this was standard knowledge (at least, it was taught in middle school and high school, even though that's been a while ago for me).

This is a fantastic video that breaks down the process, including great visual aids: https://m.youtube.com/watch?v=vuIlsN32WaE

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

#75

Post by ncmncm » Fri, Oct 02, 2020, 10:33 PM UTC

The Man Will Never Fly Society ("Birds fly, men drink") has always said it goes into the air. Funny to realize that they were right.

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

#76

Post by wahern » Fri, Oct 02, 2020, 10:34 PM UTC

thaumasiotes wrote: post #56

wahern wrote: post #54

Earlier quoted context omitted.

Sure, "it's more complicated". But the most basic, predominate mechanism is that you're literally burning carbon and exhaling CO2. Only from that realization can you start to identify and answer more sophisticated questions, including the exceptions. My point is that you can get an incredible amount of mileage from the most basic principles taught in school. Which is literally the point of a basic education. But peop…

> But the most basic, predominate mechanism is that you're literally burning carbon and exhaling CO2. Well, again, you're burning oil (or if you're starving, meat), not carbon. It's mostly carbon by mass, but not by molarity.

That's not a more accurate representation than "burning carbon". The specifics are irrelevant and can sometimes even obscure basic relationships. The point is recognizing the relationship to more familiar forms of combustion and oxidation in day-to-day life; that's how you orient yourself when you come to the question for the first time.

My middle school biology class would have been in the early 1990s when many of the finer details of cellular respiration weren't in any textbooks (certainly not middle school). It wasn't until 1996 that a critical step in ATP synthase was confirmed. But you don't need to know anything about ATP to understand the basic role of carbon in energy extraction and respiration. Actually, now that I think about it biology classes tended to focus more on photosynthesis, which sort of makes sense historically--I suppose breaking CO2 photosynthetically was for hundreds of years the far more scientifically intriguing question, and perhaps that's why it was emphasized so heavily in primary and secondary school biology.

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

#77

Post by ncmncm » Fri, Oct 02, 2020, 10:35 PM UTC

thaumasiotes wrote: post #61

mikepurvis wrote: post #47

Earlier quoted context omitted.

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 cla…

It would be nice if treatment plants did that.

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

#78

Post by ilitirit » Fri, Oct 02, 2020, 10:37 PM UTC

This is misleading in some ways. Even people who are not overweight "lose weight" through exhaling and sweat/urination. It's not really an "interesting" concept. I think the more interesting discussion is around how many people still believe that exercise is a better way to lose weight than simply eating less. Basically, the perspective is entirely wrong. It's not about "losing weight", it's about not putting into your body in the first place.

A simplification of a tangential - did you ever hear that when you first start your lifestyle change (diet/exercise) that it's very easy to lose weight at the start because you're "losing water"? Well, now you know where that water comes from.

edit: I should just also say that another interesting discussion is around the best ways to get people to eat less. And part of that involves lots of interesting (at least to me) biochemistry.

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

#79

Post by ncmncm » Fri, Oct 02, 2020, 10:38 PM UTC

thaumasiotes wrote: post #56

wahern wrote: post #54

Earlier quoted context omitted.

Sure, "it's more complicated". But the most basic, predominate mechanism is that you're literally burning carbon and exhaling CO2. Only from that realization can you start to identify and answer more sophisticated questions, including the exceptions. My point is that you can get an incredible amount of mileage from the most basic principles taught in school. Which is literally the point of a basic education. But peop…

> But the most basic, predominate mechanism is that you're literally burning carbon and exhaling CO2. Well, again, you're burning oil (or if you're starving, meat), not carbon. It's mostly carbon by mass, but not by molarity.

Most of the energy is from re-binding the carbon from protons to oxygen. Binding two protons to an oxygen yields a lot less.

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

#80

Post by ncmncm » Fri, Oct 02, 2020, 10:42 PM UTC

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…

Heat does not carry away a measurable amount of weight.