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When somebody loses weight, where does the fat go?

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Re: When somebody loses weight, where does the fat go?

#181

Post by mamon »

makemoniesonlin wrote: post #174
adekok wrote: post #38

Earlier quoted context omitted.

2 pounds a day. That's how much CO2 you breath out, and the hard limit for weight loss. You can lose more than that, (see boxers before a weigh-in), but that's all water loss, and is temporary. And, with a strong likelihood of death.

What if someone has a deficit of over 7,000 calories/day for an extended period of time (suppose they eat 3k calories and bike for 14 hours/day)?

To have such enormous deficit you would have to exercise a lot. And of course you breathe faster during the workout so I think it is entirely possible to breathe out more than 2 pounds of CO2 per day. 2 pounds if probably average for a typical person.

Re: When somebody loses weight, where does the fat go?

#184

Post by revelation »

makapuf wrote: post #115
revelation wrote: post #78

Earlier quoted context omitted.

Locomotion is incredibly inefficient, even by engineering standards. An average human exercising is about 22% efficient, that's worse than some ICEs. An electrical engine is >80%.

Electricity is not a source of energy so you have to factor in the efficiency of its production.

Why would I do that, I didn't for the human? What's the efficiency in creating cow meat, .1%?

Re: When somebody loses weight, where does the fat go?

#185

Post by aantix »

Anderkent wrote: post #125
DoodleBuggy wrote: post #31

The TLDR: > Physical activity as a weight loss strategy is, therefore, easily foiled by relatively small quantities of excess food. > Our calculations show that the lungs are the primary excretory organ for fat. Losing weight requires unlocking the carbon stored in fat cells, thus reinforcing that often heard refrain of “eat less, move more.” "Eat less, move more." If anyone isn't aware of that by now, I don't know w…

Because the problem with weight loss is not losing weight, it's losing weight while staying productive / not feeling like shit. And that is more complicated than 'eat less, move more'.

And don't forget the "maintain this for a lifetime" part of the commitment...

Because maintaining anything for a lifetime is really easy (building a business, keeping a marriage together, keeping the weight off...)

Re: When somebody loses weight, where does the fat go?

#186

Post by andrewla »

colechristensen wrote: post #130
gwright wrote: post #73

Earlier quoted context omitted.

Is this true? I was under the impression that the excess energy is due to the different bond energies of the input and output molecules and not due to mass to energy conversion.

The mass that's converted to energy in both chemical and nuclear reactions comes from differences in bond energies. Nuclear chemistry is about the bonds between subatomic particles, ordinary chemistry is about the bonds between atoms. Mass-energy conversion isn't a special thing, it's universal. All energy has mass. When energy moves, mass moves, always.

I'm reasonably certain that this is not correct; this was a viewpoint held fairly briefly in the post-Einsteinian physics community, but abandoned because of a lack of evidence.

For the purposes of general relativity, stress-energy is the mass/energy hybrid quantity, but the equivalence is not literal in the sense that in a given inertial reference frame momentum does not attach to energy, but only to mass.

Re: When somebody loses weight, where does the fat go?

#187

Post by lostconfused »

StavrosK wrote: post #50
JshWright wrote: post #6

An interesting corollary to this is "Where do trees get their mass?" Veritasium has a fun video demonstrating how unintuitive this is: https://www.youtube.com/watch?v=2KZb2_vcNTg

I love that you used the word "unintuitive" rather than imply that people were uneducated for thinking it. Good way of thinking about knowledge.

Because it's not that simple. Every moment of a person's life adds to their sum total of knowledge but it's very limited. Simply being a living human isn't going to give you a good understanding of quantum mechanics or general relativity, but it will give you some basic idea of things falling towards the ground. Something being unintuitive doesn't mean just that the individual lacks knowledge but that there is very little chance that this knowledge would be encountered in ones life time at all without making an effort to gather a deeper understanding.

Re: When somebody loses weight, where does the fat go?

#188

Post by garmaine »

smeyer wrote: post #144
Jenya_ wrote: post #139

Earlier quoted context omitted.

Losing eight pounds during 3-4 hours run (marathon event) is not unheard of: http://www.letsrun.com/forum/flat_read.php?thread=3319287

Like the previous commenter mentioned, that's mostly water. I've seen various numbers between 100 and 150 calories burned per mile for runners, which at the high end is just a bit over one pound's worth of calories for a marathon.

I’ve read about people who do things like swim the channel, and bulk up (10’s of lbs) before doing so. Given that they lose this weight in the process, how does that happen?

Re: When somebody loses weight, where does the fat go?

#189

Post by ssfsa »

kaybe wrote: post #117
makapuf wrote: post #107

Earlier quoted context omitted.

But optimize this by not running too close to c (or is it the contrary ? My restrained relativity courses are rusty)

In your reference frame nothing will be different, so it really depends on whether you want to loose weight for yourself or for others.

Except he had to accelerate to speed and back, so only our reference frame matters.

Re: When somebody loses weight, where does the fat go?

#190

Post by ssfsa »

infogulch wrote: post #160
mikeash wrote: post #4

For anyone coming straight to the comments looking for an answer to the question: it turns into CO2 (and a bit of water) and you breathe it out. When you realize that you have to breathe out all the weight you lose, I think it gives you a bigger appreciation for how difficult weight loss can be.

I was under the impression (admittedly I don't know from where) that the process of burning fat actually dehydrates you and that you need to drink extra water if you want to facilitate it. But here you remind me that the process of burning hydrocarbons nets some water, making me question myself. Of course metabolizing body fat is more complex than that, so this doesn't disprove it, but now I'm wondering if anyone els…

Dont forget that you need to cool your body, so you sweat when you work out. Also, as you breathe harder, you'll loose more moisture through your lungs (the water activity of your whatever parts in the lungs being higher than that of dry air.)

If you were to exercise outdoors during a cold rain, you'll probably not loose any water at all.

But what do I know? I've never exercised in my life.

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