I'm not saying thermodynamics is wrong, and I've never said CICO is wrong, please re-read my comment. I'm saying it oversimplifies.
An RC car with 10 bhp is faster than a truck with 20 bhp.
Putting 1000 kcal of kerosene in your engine has a completely different effect than 1000 kcal of diesel.
A 2000 kcal diet is not like another 2000 kcal diet, unless it is composed of the same foods, and the two subjects have a similar genetic makeup and gut flora.