CICO is only true in a useless sense. Do you know how much energy you are putting in? Paper (cellulose) is carbohydrates, but not used by the body; gasoline is

CICO is only true in a useless sense. Do you know how much energy you are putting in? Paper (cellulose) is carbohydrates, but not used by the body; gasoline is more energy dense than fat (at 12kcal/gr) and still unusable by the body.... So, it obviously isn’t just “carbs time 4k/cal”. Ok, let’s assume we can tell which carbs are useful and which aren’t. It takes energy to extract that energy. How much? IIRC there is over 50% variation between people (and even same person at different time) of the amount of energy actually extracted - yet almost everyone uses 100year old Atwater factors as if they were a fundamental physical constant. Glucose storage is supply based. But gluconeogenesis (conversion of protein to glycogen) is demand based, so you must be at a deficit for the 4kcal/gr protein measure to be used. How about body temp? A person at 35.6C uses a few tens or hundred calories less per day than a standard 36.7C person. Yes, these exist. Did you take this into the CO equation? Did you consider the liter of ice cold water you drank? Takes 37kcal to warm it up to body temp. CICO as usually practiced has 20-30 margin of error, which makes it much less useful than people assume. Unsurprisingly, it does work for e.g. 70% of the people, who assume the rest are not properly counting.