Eating things does not nees to invoke physics and thermodynamics lol.. It's biochemistry.
I mean, you can eat dirt, which by all rights has a certain amount of energy (E = mc2) but you're just going to **** most of it out.
I see what you were getting at, of course, but you worded it as though any energy consumed has to be rearranged.
Biochemistry, not physics ;D