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

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

#111

Post by z2210558 » Sat, Oct 03, 2020, 6:32 AM UTC

mncharity wrote: post #101

mncharity wrote: post #97

Earlier quoted context omitted.

> completely capable of doing their job [...] But then how can they miss such a trivial understanding [...] It just doesn't match up. People badly underestimate how very rapidly understanding degrades as you move away from someone's focus of expertise. You might laugh if you heard a conversation "You're a Doctor? Yes, of medieval french literature. Good, what do you think of my blood pressure medication?". Or people…

One place this underestimate hurts, is judging the expertise adequate to create excellent insightful and accessible science education content. Say you want an introduction to atoms for kindergarten. Surely a first-tier professor of physics is sufficient expertise for this, no? And yet, not so much. For example, it's possible to see an atomic nucleus with your naked eye. But only because their are a couple of oddballs…

Can you give more detail about the fluorescing nucleus? I'm honestly amazed by this (and I have a degree in physics, which I guess is your point).

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

#112

Post by SeriousM » Sat, Oct 03, 2020, 6:35 AM 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).

> I haven't opened the article

Well done...

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

#113

Post by jhrmnn » Sat, Oct 03, 2020, 7:19 AM UTC

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.

Yes, conservation of mass is to conservation of energy what Newtonian mechanics is to general relativity. The former work pretty well in everyday life

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

#114

Post by dirtnugget » Sat, Oct 03, 2020, 8:24 AM UTC

This article basically states that we cannot convert fat to energy. This seems wrong. IIRC the body can use different sources for producing energy, from sugar over carbs to fat, however it will use first what is the easiest to convert (sugar) and last what is hardest (fat). All of which is done by enzymes, I believe.

They are ignoring body heat completely. When I exercise I do not only breath out carbons, I am also generating a much higher body heat.

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

#115

Post by m463 » Sat, Oct 03, 2020, 8:58 AM UTC

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…

one hint is that rocks at the top of mountains have moss on them.

Trees are made of air.

also... 1 gallon of gasoline creates 20 pounds of CO2.

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

#116

Post by marton78 » Sat, Oct 03, 2020, 9:37 AM UTC

function_seven wrote: post #90

luhn wrote: post #86

Earlier quoted context omitted.

But mass can be converted into energy. Obviously that's not the primary weight loss driver (what a metabolism that would be!), but it certainly doesn't break the laws of physics. EDIT: Because I was curious, I did the math. Assuming diet of 2000kCal per day. 2000kCal / 3500kcal/lb fat = 0.5714 lb fat = 0.259kg fat 0.259kg = 2.329×10^16 joules = 5.556megatons of TNT 5.556megatons/day / 24 hours / 60 minutes / 60 secon…

Mass cannot be changed into energy. Maybe it can down the hall in Mr. Einstein's physics class, but here in my nutrition class we will not violate the classical laws of the universe.

Mass is converted to energy by every chemical reaction! Say you have a mixture of rust and aluminium powder, which you ignite (the thermite reaction). It results in iron, aluminium oxide and heat. The resulting matter will weigh a tiny bit less, by exactly the energy produced divided by c^2

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

#117

Post by qz2 » Sat, Oct 03, 2020, 9:37 AM UTC

baby wrote: post #100

LolWolf wrote: post #15

Earlier quoted context omitted.

> I will say that it was one of the best changes I ever made to my life. Wohoo! That's awesome, congrats! :) It is rather surprising just how much air needs to be exchanged, which is crazy and definitely not intuitive. (And I could definitely see how it could be demotivating... but, hey, we do breathe out quite a bit!)

Wow interesting. So I feel like I don’t breathe correctly. Could it be the reason why I can’t lose weight :D?

Just have to breathe a lot :)

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

#118

Post by dTal » Sat, Oct 03, 2020, 11:03 AM UTC

marton78 wrote: post #116

function_seven wrote: post #90

Earlier quoted context omitted.

Mass cannot be changed into energy. Maybe it can down the hall in Mr. Einstein's physics class, but here in my nutrition class we will not violate the classical laws of the universe.

Mass is converted to energy by every chemical reaction! Say you have a mixture of rust and aluminium powder, which you ignite (the thermite reaction). It results in iron, aluminium oxide and heat. The resulting matter will weigh a tiny bit less, by exactly the energy produced divided by c^2

The real pedantry is in the comments.

On the patented Special Relativity Diet, by eating nothing and converting your rest mass to energy, you can lose... a whopping 93 nanograms a day!

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

#119

Post by mncharity » Sat, Oct 03, 2020, 1:11 PM UTC

z2210558 wrote: post #111

mncharity wrote: post #101

Earlier quoted context omitted.

One place this underestimate hurts, is judging the expertise adequate to create excellent insightful and accessible science education content. Say you want an introduction to atoms for kindergarten. Surely a first-tier professor of physics is sufficient expertise for this, no? And yet, not so much. For example, it's possible to see an atomic nucleus with your naked eye. But only because their are a couple of oddballs…

Can you give more detail about the fluorescing nucleus? I'm honestly amazed by this (and I have a degree in physics, which I guess is your point).

A couple of nuclei have spin-isomer (IIRC) decays that emit both the expected high-energy photon, but also a second visible one. I no longer remember which. :/

The challenge with seeing a single atom naked-eye, is getting visible photons fast enough.

For some value of see - it's just a point source. I had a professor object "that's not seeing the nucleus - it's just a diffraction-limited dot". Funny thing was, they were about to travel to a big star party, to I guess "not see" stars. Sigh. Admittedly the argument for pedagogical value is limited. But at least the years-later long-exposure photo of a single atom was interesting enough for popular press.

With an atom's electrons, the bottleneck is electron transition cycle time. So your photon budget is small and isotropic. And the retina requires localized hit(s) on deadline. With an pumped atom outside the eye, even with optics, my impression is you at best have a limits-of-perception experiment: "ok, I've a 50% confidence (my dark-adapted eyes) just saw a flash there".

Nuclear transitions are plenty fast. But they're also higher energy, and you can't see X and gamma rays. Well, except for the flash of retinal cell death, as with cosmic rays in astronaut eyes.

So with a nucleus that emits visible photons, you can tweeze, trap, strip and bombard an atom to fluorescence in a vacuum chamber, have a window that passes visible, and get a little dot, naked-eye visible with ambient room illumination. It's a cover photo somewhere IIRC, but I years back burned out on trying to re-find it.

But it's a fun concept, isn't it? And makes for a compact example of needing expertise. More compact than say a marine bio professor, writing a children's picture book on photosynthesis, burning lab time to figuring out what bottlenecks world phytoplankton mass. But they're sort of toy examples. Real need is more like being able to ask "Instead of an atoms-up primary school learning progression, might we do nucleons-up to materials? What might that look like? What stories might we use? What cross-cutting ideas might tie it together?". I wish I knew how to make progress on this.

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

#120

Post by thaumasiotes » Sat, Oct 03, 2020, 4:40 PM UTC

mikepurvis wrote: post #107

thaumasiotes wrote: post #61

Earlier quoted context omitted.

> 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…

No, the point I'm making is that most of what sewage treatment plants do is deal with organics— soapy water, human waste, probably a bunch of clothing fibers, whatever. Without knowing much about waste treatment processes, I could imagine that it would be relatively easier to extract and isolate heavy metals in a state where they're otherwise just in water, vs once they're extremely diffuse and mixed in with all the…

> I could imagine that it would be relatively easier to extract and isolate heavy metals in a state where they're otherwise just in water, vs once they're extremely diffuse

This is definitely true; the more concentrated something is, the more of it you can extract.

But there are significant logistical differences between having 100,000 filters in 100,000 households doing their filtering at the point of emission, and having one filter in a treatment plant which all the water is guaranteed to pass through. What happens if 20% of the individual filters break?