Muscle memory is a real thing. If you had decent muscle mass at...

Muscle memory is a real thing. If you had decent muscle mass at some point in the past and lost it, then you put it back on really fast - way faster than you originally put it on. I am no where near physically where I was when I was in my 20s, but because I once had muscle it comes back fast - the really genetically gifted can put on 15kg of muscle in 12 months via muscle memory if they are building off a great base.

You can cut fat and put on muscle as long as you do it slowly (~1kg a month), eat a ton of protein, and are quite fat to start with. Oh you also need a lot of time.