PunctiliousKitten
Explorer
Did you know? The bulk of the fat you shed actually leaves your body as carbon dioxide on your breath, with a smaller share exiting as water!!
Something I only just learned
- Thread starter PunctiliousKitten
- Start date
unclebuff702
Explorer
I only found this out myself very recently too! Sadly, the quantity of pizza I used to put away was a good deal larger than the quantity of fat I could breathe out 
eidos
Explorer
No way!
Not a day goes by that I don't kick myself for skipping elementary school. (sarcasm)
Not a day goes by that I don't kick myself for skipping elementary school. (sarcasm)
Stace_wow
Explorer
BrightCandle
Explorer
Body fat is little more than some hydrogen, a bit of carbon and a trace of oxygen. Think of us as chemical works that pull in Oxygen, bolt carbon onto it to make CO2, and then dump the hydrogen and Oxygen out as water. The real picture is far messier, since we're also taking in plenty of hydrogen and carbon alongside small amounts of everything else to keep the chemistry running, but the bulk of our fat does leave via the breath.
LOL i didn't know... I put the question to Chatgpt myself. It let me down straight away:
Yes — that statement is essentially true, and it is a widespread misconception.
Body fat is oxidized for energy when you lose it. The atoms held in stored fat mostly end up as:
Take 10 kg of body fat being metabolized: roughly 8.4 kg leaves you as CO₂ on your breath, while around 1.6 kg turns into water that exits through urine, sweat and other routes.
So some of the mass does leave in your pee, but the bulk of the fat's actual mass ultimately goes out as carbon dioxide when you exhale.
The point that matters is that breathing harder doesn't burn more fat. The fat has to be metabolized, and that takes an energy deficit. Stored fat is then used by the body, and the carbon it contains is given off as CO₂.
So the short version is:
Stored body fat → energy + CO₂ (mostly through lungs) + H₂O (urine/sweat/breath)
Pretty neat, isn't it? In terms of mass, your lungs really are the biggest exit route for the body fat you lose.
Yes — that statement is essentially true, and it is a widespread misconception.
Body fat is oxidized for energy when you lose it. The atoms held in stored fat mostly end up as:
- CO₂ → exhaled through your lungs
- H₂O → leaves via urine, sweat, breath, etc.
Take 10 kg of body fat being metabolized: roughly 8.4 kg leaves you as CO₂ on your breath, while around 1.6 kg turns into water that exits through urine, sweat and other routes.
So some of the mass does leave in your pee, but the bulk of the fat's actual mass ultimately goes out as carbon dioxide when you exhale.
The point that matters is that breathing harder doesn't burn more fat. The fat has to be metabolized, and that takes an energy deficit. Stored fat is then used by the body, and the carbon it contains is given off as CO₂.
So the short version is:
Stored body fat → energy + CO₂ (mostly through lungs) + H₂O (urine/sweat/breath)
Pretty neat, isn't it? In terms of mass, your lungs really are the biggest exit route for the body fat you lose.
bamagirl26
Explorer
interesting, because since the weight started coming off my breathing has felt different, particularly overnight - Bye fat!!! Not going to miss ya!ZetsuM said:
LOL i didn't know... I put the question to Chatgpt myself. It let me down straight away:
Yes — that statement is essentially true, and it is a widespread misconception.
Body fat is oxidized for energy when you lose it. The atoms held in stored fat mostly end up as:
- CO₂ → exhaled through your lungs
- H₂O → leaves via urine, sweat, breath, etc.
Take 10 kg of body fat being metabolized: roughly 8.4 kg leaves you as CO₂ on your breath, while around 1.6 kg turns into water that exits through urine, sweat and other routes.
So some of the mass does leave in your pee, but the bulk of the fat's actual mass ultimately goes out as carbon dioxide when you exhale.
The point that matters is that breathing harder doesn't burn more fat. The fat has to be metabolized, and that takes an energy deficit. Stored fat is then used by the body, and the carbon it contains is given off as CO₂.
So the short version is:
Stored body fat → energy + CO₂ (mostly through lungs) + H₂O (urine/sweat/breath)
Pretty neat, isn't it? In terms of mass, your lungs really are the biggest exit route for the body fat you lose.
Turbo-Farmer
Explorer
Ketones are another thing you can breathe out, once your body is in ketosis. That smell on keto breath is the ketone acetone.
Shittersfull
Explorer
None of this was known to me. Interesting. So is carbon dioxide what fat metabolism produces?
Shadow Dancer
Explorer
Yep, that came up when I was much younger and just about hyperventilated in an attempt to breathe out more 
HereInTX
Explorer
Yep, I put the question to Chat GPT: what happens when the ventilation in your house is bad and all you do is exhale fat particles into the air, day in, day out. I'm not keen on walking into someone else's fat cloud either! As it turns out, it's nowhere near enough at any one moment to matter.