It’s one of those things, if you are losing tons of weight, you will only be able to define your muscles and otherwise so much.  This being said, one of the major things is that your skin stretches out.  So the reality is, a lot of it is probably in the stomach area, and in all things, you are probably never going to see a 6 pack.  You may have it, and good for you if you do.  But if you want to reveal it and you have that much stretched skin, which can be denoted by stretch marks all over the stomach area, you are really going to have to go in and have that professionally done, which can cost quite a bit of money. 

So in some ways you have to decide what your defined 6 pack is worth.  There is always the idea of just not gaining the weight in the first place.  But realistically speaking, that’s not something most of us are going to do.  The other thing to remember is that while you can work your abs all you want and you will build the muscle, you ultimately have to burn off the fat to get to the point where you can see it.  This means balancing out your workouts with everyday cardio.