@masa
I was challenged re my mass building strategy not too long ago and had never really thought of it in a way that could be written down and shared - very instinctive from my POV, but not really after thinking about it for a few. Sorry for the wall of text - I want to put this on paper somewhere.
I start with a base 3 meals/day diet including beers etc plus one optional protein shake between lunch and dinner - that maintains pretty much at a level bodyweight. It is fairly high in protein, about 1.2 g to kg bodyweight and fairly low in fat, 25% fat absolute max and closer to 20%. If I stop training and stay on this diet I will slowly get fat, if I increase my training load, volume, etc I will slowly burn off bodyfat, energy levels will drop and eventually I'll become angry and tired much of the time and need to increase calories or reduce training burden. This is the essence of my dietary strategy and what makes my approach to muscle building possible as opposed to the "bulk and cut" crowd.
If I really want to increase muscle I start by jacking protein to about 2g per kilo and increasing carbs and protein about equally to approx 300 calorie surplus - this is pretty easy since I don't change my basic 3 meals, I just add some snacks. This increase is accompanied by an increase in training effort or density - there has to be a credible demand for more muscle. Normally the extra calories will mostly be consumed as fuel - I won't gain any weight but will get a boost in strength and endurance, recovery will be easier. This is energy balance at a higher energy state.
I could stay on this mode and very slowly gain pretty much 100% lean muscle but it is a real high-octane approach that is tough to maintain and manage. The line between getting bigger and just getting angry is too fine and since stress levels are high it is easy to either stall on weight/strength gain or go the other way and start to just get fat and burn out.
What I do instead is keep training effort high and increase calories a second time, by another 300-400 calories or so (remember, this is all "snack" items I am deliberately adding, I'm not trying to figure any of this out by tinkering with my base 3 meals) - I like to start with fats since they are very easy to add to a diet (cue the chocolate ice cream!). This puts me into a positive balance where
most of the fats and virtually all the carbs are being consumed
but less and less of the protein is being scavenged for energy anymore - which is what must be happening if I'm not gaining muscle with a lot of protein in the diet. Now I start to measurably gain muscle.
When I notice I'm accumulating a bit of fat around the middle I know exactly what to cut - that last bit of added fats. Many people don't quite grasp this or don't want to, but the relationship between excess ingested fat and accumulated body fat is one to one. There is some leeway with excess carbs since the body stores it as glycogen and then increases resting energy output - the last thing it wants to do or will do in an exercising person is convert it to fats (excess protein is converted to carbs). And if you are exercising with intensity the body is constantly recycling lactate and replenishing muscle glucose - it will continue to burn a lot of fat even when eating a lot of carbs.
The only two variables then become training burden and that last bit of tasty fats that I can go up or down on and get changes in body fat balance visible to me on a weekly basis. There's no diet stress of "cutting", all I'm doing is reducing that part of the diet that freed up the protein to be used for
added muscle instead of burning for energy. It doesn't effect maintenance enough to talk about,
the fat I've stored is equivalent to a small surplus and it gets burned up almost no different than if I were at a lower % bodyfat and were eating a little more dietary fat.
This is the second thing a lot of people don't quite grasp but what makes it possible to gain muscle "at maintenance" or as is often talked about "gain muscle while losing fat" that is supposedly only possible for beginners. Granted, everyone is different, and the body will start to steal increasing amounts of protein for energy as your bodyfat % drops or if you try to supplement too much maintenance energy from stored fat. But...if muscle mass starts to decline along with bodyfat you can either increase protein (no point in doing this if its already really high), or increase carbs, which will have the same effect by sparing protein for muscle maintenance. We're now coming back around full circle to the initial diet strategy for maintenance.