Next, it is important to clear up that we can’t assign macros to someone without first having an idea of what their energy requirements are. You want to have the calculator tell you want to do for lean muscle mass? Then you have to know your energy requirements for your goal first and foremost. Get this before you begin to break that into grams of macronutrients.
Think of a house. The square footage is like your total caloric requirements. Let’s say you have a 2000 square foot house (or 2000 calories). You decide to break that house up into 3 bedrooms, 2 bathrooms, and 3 communal living spaces (kitchen, living room, dining room). Or you could also do a (4, 2, 2) breakdown. This would change the total space for bedrooms, communal spaces, and bathrooms, but the house dimensions aren’t going to change.
So if we take your daily 2000 calorie requirement and break it up into macros evenly (33/33/33%) or decide to bias one over the other (50/25/25%) you aren’t changing the total calories you eat.
I would argue, as would many of my colleagues in the fitness industry, that if you hit your caloric goals you’ll see favorable changes to your body. If you get sufficient protein in your diet, you will see even more. The rest is really just a matter of personal preference.
If you want to go high carb or low carb, it really doesn’t matter so long as you hit those other two metrics, protein and calories, consistently for a long time. So the way we must understand the other macros, fat and carbs, is in the context of what helps support the most consistency.