Thing is, even if a calorie is a calorie is a calorie, a body isn't a body
isn't a body.  How calories are used is going to differ amongst individuals.

A fun aside, but relevant: An online acquaintance did a week-long challenge
in which he ate 4,000 calories each day (he tracked in a program, like
Fitday) from meat and fat only.  He did not change his exercise regime (not
much of one) or anything else, just that.  He'd already been eating low carb
and paleo for some time AND had shed excess bodyfat along the way (he's
tall, but quite lean), and he still lost a pound.  

Anyone else wanna try it?  ;)

Tracy