It is, however, the final word.
Thank you for that. Now if you'd like to adopt the assumption that your audience isn't brainless, let's talk about the interesting point that everyone wants to be talking about: that the 'calories out' number varies for the same 'calories in' number across people, diets, and behaviors.
If you can demonstrate everywhere the energy comes from and everywhere it goes and where and how it's used in the body, I imagine there's a nobel prize in it for you. There's still a lot we don't know about where all that energy comes from and goes.
Weight loss...
>And the energy needed to convert complex carbs and protein into glycogen?
Energy out...
>The energy used converting glycogen to ATP?
Energy out...
The body is complex. Energy in - energy out = weight lost its not.