I understand that when the human body loses weight, the vast majority of that weight is lost as $CO_2$ (and a small bit is lost as water). I expect the predominant way $CO_2$ exits the body is through exhaling.
So, let's take a human with no influx of carbon (they are not eating); I expect such a person is slowly losing weight, a near infinitesimal amount with each breath (correct me if I'm wrong).
If the person breathes faster (more breaths per minute), that causes an increase in the rate at which $CO_2$ is expelled, correct (more mass per minute)? Is this rate expected to decrease, i.e., as one breathes faster, less $CO_2$ is contained in each subsequent breath? Or, does perhaps the body mobilize and oxidize carbon fuels (carbohydrates first and eventually lipids) to generate $CO_2$ in an attempt to restore homeostatic equilibrium?
Could breathing quickly and heavily possibly cause an increase in the $CO_2$ content of exhaled breaths? That is, would voluntary hyperventilation cause an increase in heart rate (and thus increase in carbon catabolism)? How much $CO_2$ is in a typical exhalation during exercise?
I realize that without exercise, the amount of $CO_2$ being lost during normal breathing is nearly negligible. But perhaps laying down and breathing quickly could cause a measurable increase in the net rate at which mass leaves the body. What do you think?
Thank you for your time.