Short of putting someone within a closed system vessel and counting the energy which goes into the vessel and the energy which comes out of the vessel you will

Short of putting someone within a closed system vessel and counting the energy which goes into the vessel and the energy which comes out of the vessel you will never get an accurate measurement of CICO. It is relatively easy to measure the calories you intake via food/drink since that can be roughly approximated using lab tests, but there is basically no accurate way to calculate the amount of calories somebody expends. I haven't heard of anyone counting calories running their shit and urine through a calorimeter to figure out how much of the energy in their food was absorbed by their body and this isn't even counting energy expended through heat, skin/nail shedding, and breath. The article should have said "true CICO is impossible since measuring calories out is practically impossible" instead of "CICO doesn't work".