I lost ~70 lbs on WW, and trust me, you need to use your activity points!
In fact, I used to use all the points I had available unless I started gaining - which I really never did. I lost the first 30 or so without doing any exercise, then added some aerobics classes, and later I began running. Your body needs fuel to exercise, and that's what the activity points are for. WW will tell you not to use more than 4, but what I've read suggests that they don't want folks overexercising (what's that
) so they can eat more. If you're running 20 miles a week, you need more food - and of course, it should be good nutritious food not cokes and candy bars.