This brings us to our final law when it comes to building muscle. Simply put: muscles don't grow unless they are properly fed! That's right, calories count a lot more than just when we're talking about weight loss.
When you're in a calorie deficit your body's ability to repair and grow muscle tissue is impaired. This is why workouts take a bigger toll on you when you're dieting, and why you have to accept slower or even no muscle gain when you're dieting to lose fat. Sorry but that is reality, however if you are maintaining muscle and losing fat, the net result is a better body composition.
Remember calories are what fuel every process in your body and the requirements for muscle building are very metabolically expensive. Therefore, if you want to maximize muscle growth, you need to make sure you have a slight surplus of calories (you are taking in more calories than you are burning). But not just any calories, in order to “feed your muscles”, eating enough protein is critical. In fact it’s just as important as eating enough calories when it comes to muscle growth.
Having said that, don't misunderstand me and think that protein is what fuels your muscle building efforts. This is where carbohydrates step in as the preferred fuel source of the body because they are converted into glycogen which is stored in the muscles and liver and is the primary source of fuel during intense exercise. When you restrict carbohydrate intake, your body's glycogen stores drop, and studies show at this point genetic signaling related to post-workout muscle repair and growth is inhibited. On a hormonal level, restricting carbs also raises your cortisol and lowers your testosterone which further inhibits your body's ability to recover from challenging workouts which is when muscle tissue is built.
In summary, all this research shows that athletes who eat low-carb diets recover slower from their workouts, gain less muscle, and make minimal strength gains compared to those who eat more carbs to fuel their exercise. When you don't have the fuel necessary, you can't progressively overload your muscles and therefore maximum muscle protein synthesis is never achieved…that means muscles can't grow.
So what about dietary fat? Fat is necessary to maintain anabolic hormone production, in particular testosterone production. BUT be careful of overdoing dietary fat because these effects can quickly be erased when too much dietary fat makes up your overall calorie intake and starts to limit your ability to take in quality carbohydrates and protein. In short, you need some high-quality healthy fats but they should be a small part of your overall caloric intake and get the least amount of prioritization in your diet when it comes to building muscle.
You could spend hundreds of hours studying muscle growth and the human physiology behind effectively growing muscle but you would still barely scratch the surface. Fortunately, you don't need to understand all these physiological processes when it comes to improving your strength, building muscle, and improving your overall muscle tone/body composition. To summarize the three articles on building muscle, you just have to know progressive overload with weight lifting causes muscle damage and when you fatigue your muscles in your workouts, you need to feed them properly afterwards. This repair process is what produces muscle and strength gains. Stress, nutrients, recovery, adaptation = muscle growth.
Now get out there and work hard in the gym and eat to recover because your body is a machine made to build muscle you just have to put in the work.