I think some doctors actually are stupid or at least narcissistic. But I do see your point here, also want to point out the absurdity of the graph chart they included. However the CO2 is released with activity then exhaled. That is to say we do not lose weight just by breathing alone. (would that we could!) So the energy has to be released as you said, first with activity then exhaled as carbon dioxide.
I think some doctors actually are stupid or at least narcissistic. But I do see your point here, also want to point out the absurdity of the graph chart they included. However the CO2 is released with activity then exhaled. That is to say we do not lose weight just by breathing alone. (would that we could!) So the energy has to be released as you said, first with activity then exhaled as carbon dioxide.