...when building muscle?
From what I've read, it seems that protein is broken down into amino acids, many of which humans can't synthesise themselves, and then these are used to build new muscle fibres during the repair stage that follows muscle damage from lifting heavy weights. So increasing protein, up to the point where more protein can't be effectively used in this process, encourages muscle growth.
But what do the fats and carbs do besides provide energy for workouts? And is there any benefit to eating say 5000Kcal/day rather than 3500 when bulking up? What happens if someone eats their 'maintenance' (RMR+Energy expended from exercise, moving about etc) with 1.5g+ of protein/ lb body weight and the rest from a balance of good carbs and fats (whilst also lifting heavy)?
I've seen some people taking 'weight gain' shakes that have massive amounts of sugars etc. in them which surely just leads to gaining fat and doesn't help much with building muscle?