[coldtea]

But you seem to be the only one assuming and/or bringing up rigor in this discussion.

Everybody said it's a quick ballpark figure / back of the envelope style calculation.

The mere fact "cake bad, carrots good" everybody knows. It's not much information concerning "Did I ate too much today?". One can have a caloric budget and stay within it (more or less) without having to be perfect in measurements (or sticking to carrot because it's easier to know its light).