The question of 'how to build lean muscle' is actually a misnomer. This is simply because muscle and fat are two very different types of tissue. For this reason, there's no such thing as "fat muscle" or "lean muscle." Sure, there's such a thing as a muscular person who also possesses a lot of fat. Likewise, there are muscular people who just happen to be very lean. But muscle can't be fat and fat can't be muscle. Therefore, there is, technically speaking, no such thing as lean muscle.
Why do I insist on such semantic clarity? I do it because it leads to an understanding that's vital for becoming a lean and muscular person. If the question of 'how to build lean muscle' is really a parsed version of "how do I become a muscular person without becoming fat", important distinctions drawn from semantic corrections are likely in order. In short, learning to build muscle is a topic in and of itself. Learning how to get lean is its own topic as well. So knowing 'how to build lean muscle' is really a matter of learning how to build muscle without gaining fat and how to lose fat without losing muscle.
With those distinctions as a preface, let's delve into the subject people often refer to as "how to build lean muscle."
'How to Build Lean Muscle': Just say "No" to Mega Calories
In the past half-century of bodybuilding, the mega-calorie trend has reared its ugly head in popularity at various times. It's manifested in the belief that in order to build muscle as rapidly as possible, one needs to slam down heavy calorie loads. The assumption is that all those excess daily calories will just find their way to starving muscles, with accelerated tissue growth being the result. It seems reasonable at a primitive level. What could seem more plainly logical than the idea that gaining bigger muscles is mostly a matter of eating bigger meals? But is it really true?
The mega-calorie myth doesn't stand up to common sense when considering that muscles grow while recuperating and recuperation occurs at a fixed rate of speed. Any calories consumed beyond what're needed to meet that recuperation rate will not only be unhelpful to muscle growth - they'll likely be converted to fat. This is, obviously, the antipathy of 'how to build lean muscle.' Worse, it often inadvertently ends up as the prescription for how to build more fat than muscle.
To illustrate this point more clearly, I've often cited personal information shared by a top pro bodybuilder many years ago. It happened when I attended a bodybuilding seminar. The bodybuilder was a top Mr. Olympia contender. He was, admittedly, a heavy steroid user. When asked by one of the seminar attendees "how fast can you gain muscle", he answered that he was currently gaining about two pounds of muscle a year. He contrasted that with the rate at which he gained it as a beginner: "About ten pounds per year."
Think about it: An elite pro bodybuilder, great genetics, avid drug user, terrific nutritional knowledge and practice. But it took him a year to gain ten, solid, dry pounds of muscle at his fastest rate of growth. That's a "whopping" .027 lbs. of muscle per day. It's close to .2 lbs. of muscle per week. It amounts to requiring a little over five weeks for gaining one pound of muscle.
With this in mind, does it really stand to reason that we need mega calories each day to build muscle, even at its fastest rate of growth? Does it make sense to need a "bulking phase" in which we consume many times the calories needed for daily energy, workouts, and recuperation? That's unlikely.
So the first tip on how to gain lean muscle is to refrain from falling for the mega calorie myth. Yes, we need enough protein, carbohydrate, and dietary fat each day for energy requirements and tissue recuperation. But those few extra required calories shouldn't add up to anything more than 300 to 400 calories above maintenance level.
'How to Build Lean Muscle' by Avoiding Overtraining
One practice that often leads bodybuilders to overeat is overtraining. When muscle growth hits a plateau, it's often assumed that higher calorie intake will fix the problem. But more often than not, the body just needs more rest days between workouts. In fact, a big secret in how to build lean muscle is to understand that nothing else will compensate for the need of the muscles to get whatever number of inter-workout rest days that are required given the degree of tissue breakdown imposed.
What does this mean?
It means that if you finish an intense bodybuilding workout, you'll need quite a few non-training days to rest, recuperate, and grow. And if you finish a workout of even greater intensity-of-effort than that, you'll likely need even more rest days to grow. Ironically, at that point you might need additional rest days while requiring even fewer daily calories than you're currently taking in.
It's important to understand that muscles recuperate and grow between workouts in a fairly steady and methodical manner. Yes, this requires an adequate amount of calories; nothing less will do. However, any forced-down calories beyond the adequate amount will not stimulate the muscles to grow any faster. In fact, it might slow down their growth as the digestion and processing of excess food can sap precious recuperative energy from the body.
Overtraining results from not allowing enough inter-workout rest days given a specific amount of workout volume and intensity. Or it's the consequence of applying too much volume and intensity given a specific number of rest days. Obviously, one's just the inverse of the other here. The point is that you need to optimize the ratio of work to rest days. Once you do, muscles will steadily get bigger without your waistline getting fatter. This eventually leads to a leaner and more muscular body without consciously dieting. And that's a major key in 'how to build lean muscle.'
'How to Build Lean Muscle' by Balancing Macro Nutrients
When bodybuilders inadvertently gain fat along with muscle, they often need only clean up their eating habits slightly to shed the fat. One of the easier ways to do this is by cutting back on carbohydrates a bit while slightly increasing protein to preserve muscle tissue. In other words, a key tactic for 'how to build lean muscle' is by improving your balance of macro nutrient intake. If you follow a rough intake of carbohydrates at 40% of calories, protein at 30%, and fat at 30%, it's fairly easy to gain muscle without body fat. This will be the case, of course, provided you follow the previously mentioned advice: Don't over-train and don't over-consume calories. Taking in a more balanced ratio of macro-nutrients becomes the "finishing touch" piece of the puzzle for how to build lean muscle.
Does the macro nutrient balance need to be exactly 40/30/30? My personal experience has told me otherwise - that something close to that ratio will do the trick. In fact, it might be better to ratchet up protein so that it's about 40% of calories while carbs and fats are each 30% (respectively) if body fat has begun creeping upward. That's because the body uses up more calories to digest and process protein than it uses to digest and process carbs and fats.
When you add in the fact that protein foods produce more satiety while also preserving muscle tissue, it becomes obvious that intake of this macro nutrient is a big factor in how to build lean muscle. Lay down some grams of protein in your stomach with every meal you consume. Don't eat carbs and/or fats by themselves.
If you follow that simple eating advice along with an optimized ratio of workout days to rest days, you'll have a solid foundation for building lean muscle - the acquisition of muscle mass with minimal or no added body fat.