Protein protein protein.
I did a liquid diet last year and lost about 160lbs of fat - weight that I've kept off even after the diet by a strict excercise regimen and protein intake. I never ever want to lose my muscle mass, just get rid of the flab. My doctor says that I'm built "like a Peterbilt", and that anything under 225-250 will be downright anorexic for my frame. Funny how much BS the BMI is
Anyway, keep up the weights and LOTS of protein - but don't overkill the protein. Consult with a good doctor and excercise physiologist to find the amount that is right for your body.