Why does muscle gain require extra calories?
I've heard that if you want to gain muscle, you need to consume more calories (not just extra protein) than you burn. Why does this requisite exist? In other words, what does this extra energy do for muscle gain? Can anyone help me with the physiology behind this?
The only answer I can come up with is that a lot of energy is required to transport large quantities of protein and other necessary nutrients to the site of repair, and this energy wouldn't be available in a calorie-deficient diet. But first of all, am I right in assuming that such a large amount of energy is really required for this purpose, and if so, couldn't the body simply burn existing fat stores to fuel the task?
It's been boggling my mind for ages.