A PSMF a la Lyle McDonald's Rapid Fat Loss is the fastest way to strip off fat without losing too much muscle. Losing 4+ lbs of pure fat per week in the beginning is very typical. Fat, not muscle, not water. You will lose your sanity, however, eating nothing but chicken breast, egg whites, white fish, and green leafy vegetables for weeks on end. The periodic carb-ups give you some sanity, but not much. When I did the diet, I also suffered from nausea, headaches, and constant brain fog.