You are always breathing, but you breath about 3x more while you're working out cardio style, but you're not significantly changing your average breath rate for the day unless you're working out for hours daily. 24 "rest-hours of breath" on a lazy day, 26 "rest-hours of breath" on a day when you spend a full hour doing cardio/running/etc, so spending an hour doing intense workouts only increased your carbon exhaled by 8.3%. Also, somewhere around 2/3 (if not 3/4+) of the weight you lose per breath is simply water vapor restored when you have your next drink, not carbon atoms being attached to oxygen molecules in the air. Also, working out makes you hungry, rightfully so (in a world that isn't essentially full of infinite tasty food for those of us with a little money). The only way to lose significant weight is to feel hungry, and to stop eating before you "feel" full. This is de facto psychologically insurmountable (or nigh unsustainable) to everyone who is overweight and wants to lose it but just can't bear to be hungry enough for long enough. Spoken as someone slightly overweight who just needs to feel a little hungry for a couple months to get to a much better weight. And of course, once you've made a habit of eating over your ideal calories, even after you've lost the weight, your stomach is still bigger and it's effortless to go back to eating your usual large-self amounts even after you've lost all the weight, and go right back to large-self weight.

I can't remember where I read it unfortunately, but yes, breathing harder will contribute to weight loss.

edit: https://www.healthline.com/nutrition/breathing-exercises-for...

I love how he captures it in a balloon during this Ted talk on fatloss. https://www.youtube.com/watch?v=vuIlsN32WaE

The problem with working out to loose weight is that your body knows it takes more calories and so it happily ups your appetite

I don’t see why these things must be as interconnected as you’re question suggests.

If you have a relatively constant outflow of breath, measurably but not drastically affected by exercise, the CICO conception could still account for the net difference in body mass.

Your exhalations are a direct result of the chemical reaction that gives you energy: C + O2 -> CO2. C is your carbon-based food, O2 is your inhalation, and CO2 is your exhalation. When you burn more calories, you increase the speed of that reaction, and you breath out more CO2. That is why exercise makes you lose weight (and why it makes you heat up). They are inextricable. The mass has to go somewhere!

the fork is mightier than the metabolism!

the breath thing is how the metabolic waste products leave the body (when your fat gets broken down eventually the mass of it leaves your body as co2).

also, the amount of hours you spend not working out dramatically trumps the amount of hours you spend not working out so working out itself doesnt change your mean..