You can measure calories burned pretty accurately by measuring CO2 exhaled. Measure the concentration of CO2, the length of the exhale, and the force of the breath and multiply to get a quite accurate view.
Hmm, you might also be able to use a pulse oximeter to measure dissolved CO2, plus a chest band to measure respiration. Dissolved CO2 should more or less match CO2 concentration in breath, so you would not need a visible cranula on the nose.
Carbon is not the only thing the body burns, hydrogen too, which makes water which can't be used to measure calories, but because the majority of what we eat has about the same ratio of hydrogen to carbon, measuring CO2 should be enough.
Hmm, you might also be able to use a pulse oximeter to measure dissolved CO2, plus a chest band to measure respiration. Dissolved CO2 should more or less match CO2 concentration in breath, so you would not need a visible cranula on the nose.
Carbon is not the only thing the body burns, hydrogen too, which makes water which can't be used to measure calories, but because the majority of what we eat has about the same ratio of hydrogen to carbon, measuring CO2 should be enough.