I'm not a doctor or nutritionist, so do some research before you buy into this, but I read somewhere once upon a time that in order to physically move protein m

I'm not a doctor or nutritionist, so do some research before you buy into this, but I read somewhere once upon a time that in order to physically move protein molecules into your muscle cells where they can be used to repair said tissue, you need carbohydrates. One frequent criticism of things like the ketogenic (aka "atkins", "low carb" etc.) diet/lifestyle is that you almost can't gain muscle on it at all, even with the perfect routine otherwise in place. Takes a very long time by comparison. So just make sure that you're not doubling down on 100% protein with no carbs in there. I'm not sure what the "best" split is there, but I'd start at 50/50 and tweak as needed. Regarding fats: while they are more than double the energy density per gram than protein or carbohydrate (9 cals. vs 4), they're also far more satiety-promoting. In other words, if you're filling up on fats, you're getting calories, but not necessarily the ones you may need to start building useful new tissue. Obviously zero fat is crazy (and unhealthy!), not to mention it makes things taste awful, but try to avoid the temptation to just suck down a lot of fat. You'll feel too full to get much of anything else!