Calories aren't equal, otherwise you'd feel sated for the day with 2000 calories of sugar (spoilers: you don't). Every year, we're finding out how much we still don't know about the body regulates our fat stores via hormones. Dr. Jason Fung is a leading researcher on this (https://www.youtube.com/watch?v=ZKC3hiyLeRc)

The second law of thermodynamics is defined on closed systems, so unless you are the type of person who doesn't eat or breathe then it isn't really applicable.

It is rather like saying E=MC^2 is good diet advice.

That's not to say CICO isn't true, but trying to link it to base physics is a red herring.