I've been wondering about this one for a little while. This guy at my gym that competes said that you'll put on more muscle mass if you have a decent amount of bodyfat on you.
Also one person in another thread said this:
You might have to sacrifice single digit body fat to pack on mass for your chest. I'm talking about lean bulking here. Would you mind bumping your body fat up in the 10-12 % range if that means packing on quality slabs of chest muscle?
So what's the deal?!