I attribute it to a body composition change. You literally have to train your body to run on different energy sources. I always recommend people drop down as lean as they can get before they start eating heavy. I remember my friend who used to bodybuild was always lean and eating garbage and i could never figure it out. It wasn't until after dieting down a few times that my body started to function the way i wanted it too. I always tell people the best way to grow is to drop down until you can go no further and then to start cramming the calories down. It will get to a point where your BMR will increase and it will be very difficult to store fat. Another thing that is strange with me is that i have difficulty growing when i'm eating a lot of calories/ bulking. I notice when i'm dropping body fat i have growth spurts. I think a lot of this has to do with the fact that you have insulin receptors in your fat and i THINK you have androgen receptors in your fat as well.... not 100% sure on that though. Someone correct me if i'm wrong. When you burn this fat you have more open receptors in your muscles.
no it's just an optical illusion, at a certain point enough fat melts away so that you see more of the muscle. At low tide rocks look bigger, but' it's not because they have grown.