There is no magic to getting lean. Burn more than you take in. Period. Not drastically but say you eat 2000 calories but you burn 2300. You just got rid of 300 calories and hopefully its from fat. The body doesnt go into starvation mode and start burning muscle.( hopefully) But if you cut the calories to much the body will burn muscle for energy. And yes you can lose fat eating just carbs or just fat or just protein or a combination of them all. The "trick" is to just burn more than you eat. people are so mislead. watch the commercials now on tv. All about "protein" for energy etc or protein packed etc. Because people think they can eat alot of protein and not gain weight. Same way with keto. They think they can eat anything that has fat and not worry cuz they are doing keto and then they gain 20 lbs. LMAO. ( keto works great by the way but only when done properly and its not for everyone)
You are absolutely right, that's the way to get lean, burning more than you eat can put you in any bodyfat % you want.
I deeply apologize if I sound like a asshole, but when we go into the trouble of giving an answer I think we need to go a little further than that.
What I mean is that although this is the way to get lean we have to keep in mind that lean is not equal to shredded as in photoshoot ready, and I think that is the goal when someone try to get lean in bodybuilding terms.
Even though you can get to 7-8% merly eating less than you burn off, one thing that you have to know, that nobody seems to tell, is that you can and will! look like shit even at 7% if you don't know what the fuck are you doing.
Its far for being rocket science, but in order to look photoshoot shredded you need to know the best ratio for the macros, that works best for you and help you achieve the body composition you want.
You also have to know how to play with sodium, diuretics and stimulants like ephedrine.
No one can have that kind of look out of nowhere, even if lean you have to prepare yourself.
It is very common to see fellas walking around 8% looking like michelin man and disappointed on how they seem to never look good even if they are in a caloric deficit for 30weeks. They think that there is some kind of secret on how guys get prepared in 16 weeks, they think that getting shredded is some kind of magical knowledge or ability or god know what
Like you said, there is no magic, but to one be able to pull this off he need to have lots of trial and error under his belt, and I mean really trial, taking the time needed to really see what works for you.
The best one can look for is having the correct guidelines in different approaches, but there is no other way around than trial and error in your own body.