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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?

#71

Post by mikeash »

xhruso00 wrote: post #56
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.

Can I lose weight by breathing faster instead of excersizing?

Merely breathing faster won't help. Each breath will just remove less CO2. What you need to do is produce CO2 faster, which means increasing your metabolic rate somehow. That generally means exercise.

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

#72

Post by killjoywashere »

arikrak wrote: post #64
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.

But you also breathe in co2 with every breath so would need to subtract that..

the inhaled partial pressure of CO2 is 0.3 mmHg. The exhaled partial pressure is 35-45 mmHg. The inhaled CO2 would be lost in the rounding.

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

#73

Post by gwright »

colechristensen wrote: post #45
orblivion wrote: post #29

Earlier quoted context omitted.

But not the conservation mass-energy. What's to say we're not burning off our fat in a nuclear reaction? :-D

Chemical reactions undergo the same mass loss as nuclear reactions. A fat molecule weighs very slightly more than the sum of it's parts. The resulting water and carbon dioxide products will weigh less than the reactants by exactly the amount of energy released. It's just much more difficult to notice because the amount of energy released is as much less.

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.

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

#74

Post by mikeash »

stepanhruda wrote: post #34
xisbad wrote: post #23

Earlier quoted context omitted.

So does that mean that sitting on the couch is more environmentally friendly than exercising?

No it means not eating is more environmentally friendly.

The food you eat will turn to CO2 one way or another. If you let your food become fat rather than CO2, that fat will eventually turn into CO2 after you die.

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

#75

Post by eropple »

StevePerkins wrote: post #37
Zanta wrote: post #12

Earlier quoted context omitted.

From the paper "Replacing one hour of rest with exercise that raises the metabolic rate to seven times that of resting by, for example, jogging, removes an additional 39 g of carbon from the body, raising the total by about 20% to 240 g. For comparison, a single 100 g muffin represents about 20% of an average person’s total daily energy requirement. Physical activity as a weight loss strategy is, therefore, easily fo…

I can't help but groan at some of the "obvious" health and weight loss platitudes that get smugly thrown around. " Calories in, calories out! " " You can't outrun a bad diet! " " Weight is lost in the kitchen! " Sure, things ultimately boil down to intake-vs-expenditure. However, it IS more complicated than that in practice . As software developers, we complain when management makes decisions based on inadequate or p…

> They're constantly dabbling with soylent shakes or paleo/keto fad diets... because the truth is they're just lazy and don't want to get off their ass, and look to rationalize that.

This is a stretch to me. Doesn't matter how much I exercise: aggressive keto diets are the only way I've ever lost weight (though not necessarily maintained it, I can maintain on a normal diet) in my life. Playing two games of full-court basketball a day or sitting around playing video games, I'm just not as hungry and the food I eat when I'm going that route just doesn't stick the way it can otherwise.

I certainly feel better, you're not wrong about that, when I exercise even moderately. But the diet matters plenty, too--it's yet another one of those more complicated in practice things that you're claiming exist in the first place.

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

#76

Post by colanderman »

srcmap wrote: post #52
Zanta wrote: post #12

Earlier quoted context omitted.

From the paper "Replacing one hour of rest with exercise that raises the metabolic rate to seven times that of resting by, for example, jogging, removes an additional 39 g of carbon from the body, raising the total by about 20% to 240 g. For comparison, a single 100 g muffin represents about 20% of an average person’s total daily energy requirement. Physical activity as a weight loss strategy is, therefore, easily fo…

I wish there is a way to allow one to enjoy eating but control how much to absorb the food.

I'm not sure whether you're being serious, but as a serious answer, that unabsorbed food has to go somewhere. See: https://en.wikipedia.org/wiki/Olestra#Side_effects

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

#77

Post by bluGill »

xhruso00 wrote: post #56
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.

Can I lose weight by breathing faster instead of excersizing?

That is a form of exercise, so in that sense yes. It isn't significant, even on the scale of a year, but it is something we can calculate.

For practical purposes no. When you breath faster your body just gets rid of less CO2 per breath. The amount of CO2 your body creates for a given exercise level can be considered a constant.

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

#78

Post by revelation »

Filligree wrote: post #26
k__ wrote: post #15

Earlier quoted context omitted.

200g are what would be "breathed out" in one hour without exercise? So you can only increase your "burn rate" by 20%?

A remarkable fraction of your energy consumption is spent on basic maintenance, and of the rest, far more than you'd think is spent on the brain. Your body is extremely efficient, by engineering standards, but that includes locomotion. Exercise is still a good way to drop in weight, but not simply due to burning up the fat; that could happen anyway. What seems to be happening is that the exercise improves the body's…

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%.

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

#79

Post by StevePerkins »

beardbandit wrote: post #49
StevePerkins wrote: post #37

Earlier quoted context omitted.

I can't help but groan at some of the "obvious" health and weight loss platitudes that get smugly thrown around. " Calories in, calories out! " " You can't outrun a bad diet! " " Weight is lost in the kitchen! " Sure, things ultimately boil down to intake-vs-expenditure. However, it IS more complicated than that in practice . As software developers, we complain when management makes decisions based on inadequate or p…

"I can't help but groan at some of the "obvious" health and weight loss platitudes that get smugly thrown around." On the flip side, the people that are told this are the ones that are annoyingly attempting to maintain their bad eating habits while just adding exercise, or adding fab foods, or anything really to delude themselves into thinking they can continue to eat the same way.

I have never in my life met someone who has the physical and mental discipline to exercise regularly, yet also still sits around eating candy and pizza the other 23-hours of the day.

MAYBE if you're still in school, or a new grad in your 20's, you might know people who are physically active but also like to drink heavy / party. But by the time you're 30 or so, exercise and decent eating habits tend to correlate one way or the other.

Whenever someone strikes up a conversation with me about exercise being of minimal importance compared to diet... it's usually when I'm heading downstairs for a workout in the company gym, and some brogrammer with an energy drink in his hand takes it upon himself to justify why he isn't.

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

#80

Post by SketchySeaBeast »

yetihehe wrote: post #47
arkh wrote: post #13

Earlier quoted context omitted.

It's easier to eat less calories than exercise.

Have you tried it? I did, it's easier only for some time. After you lose about 6-7% of your body weight it's very hard to eat less, your whole behaviour changes.

Is there statistics for this? I recently dropped 20% of my bodyweight, but didn't find that my behaviour changed at all. If anything as the routines set in it became easier.
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