Every person is different, but I lift heavy and still lose fat. I average about 1.5 lb. loss per week. After losing about 50 lbs. I hit a 2 month plateau and someone suggested I try Cathe lifting and I got pyramids and now I'm losing again, almost down 60 lbs. I think maybe that extra muscle is helping to burn the fat all the time or gave my metabolism the kick it needed. Also, I frankly find that I have more confidence and feel firmer since adding the heavy lifting. Feeling better makes it easier to stay motivated to eat correctly and exercise...positive cycle.
If you want more details on my current rotation check my website. I'm planning to change over from pyramids to S&H in May. I plan to keep lifting heavy till I reach my goal and beyond. I will say that I do a lot of cardio however. 4-6 hours per week plus yoga and some "lighter lifting". So I just mix it up and keep the body guessing.
Those of you doing WW, please stop by the Fitness Challenge board on ww online (you don't have to be a subscriber to use the boards). We have a Cathe Challenge Group that posts daily of people who love Cathe workouts and are on WW.