Leaning Out

Does anyone notice they are having great difficulty loosing their fat layer around the mid-section after bulking up?  I have a nice little layer there that I have been trying to work off, yet at the same time, maintain the muscle mass that I developed.  Ugh, fricken insuling I am sure is playing a factor.

IDEAS????

I notice it a little on my obliques, but not the front of my abs. I figure the lower layer of fat...not necessarily gross, but not the bottom part of my 6 pack either haha is probably there from food/beer. I've changed my diet and am doing a pretty intense training regiment and I've noticed a lot of fat loss.