Does having a high metabolism make a person excrete more?

The speed of your metabolism is how fast you burn energy, not process energy. When you burn energy, the byproducts (CO2 and H2O) go into your bloodstream. Thus, these get exhaled. If your metabolism is higher, you will exhale slightly more, or you will have a higher concentration of CO2 in your breath. read more

If your metabolism is higher, you will exhale slightly more, or you will have a higher concentration of CO2 in your breath. The only things you excrete are what your digestive system does not need. Thus, not excreting much can be a sign you are eating very nutrient-rich foods. read more

More likely, as a friend pointed out, an older person with a "slower" metabolism is simply doing less physical work (perhaps due to learning how to do things more efficiently), not exercising, not fidgeting, living in comfortable climate-controlled surroundings, etc. read more