(Weight/mass used interchangeably; assume gravity is constant)
We obviously gain weight by eating, but we also have to gain a little mass when our lungs absorb oxygen. Similarly, we lose some mass by excretion and exhaling, as well as by perspiration and simple disconnection (dandruff, amputation). Is there anything known about the relative size of these effects as they pertain to whether one gains or loses weight? The best I can find is that there are some media reports on how a study found that 80% of fat is lost through breathing out. Well, of course, because generally carbon leaves your body via breathing, while the hydrogen stays around in some other form, or excreted as part of water or whatever.
There are a number of things I’m interested in here.
What is the (average daily I guess?) net weight gain or loss from inhaling oxygen and breathing out carbon dioxide? I’m assuming it’s a loss as we merely use oxygen in “burning” the carbon sources, and breathe out as many carbon dioxide molecules as oxygen molecules we breathe in (as each has 2 atoms of oxygen), and the former clearly have more mass.
What is the *total *(avg dly) net weight change from inhaling and exhaling, including things other than oxygen in and carbon dioxide out? I believe that the most important thing here is the net exhalation of water, which should occur at any time the humidity is below 100%.
How much of your net weight change is from dead skin falling off, assuming you don’t have ridiculous dandruff?
What is the percent net change in mass between items ingested and excreted? How much of the mass are we actually taking from food and later exhaling or perspiring?
How much water is created as a product of cellular respiration as a percentage of the water that we ingest in any form?
I assume that the body regulates water such that we tend to have exactly as much as we need, and that the proportion of our body that is water is relatively constant, but is there is tendency to have that proportion go up or down slightly as we add on fat? What about muscle?
I’m sure there are other interesting things related to this too that I haven’t been able to formulate, so any numerical information related to this topic would be appreciated.