I have about 20 or so pounds to lose, and its definitely slower going than if I had 100. I lost 6 lbs on P1, then have been averaging about a pound a week since then. But I DEFINITELY love that SB has given me control over my relationship with food... i used to literally graze all day, every day, and now I can't even imagine doing that. WW never worked for me because I was always hungry, and I literally am never hungry outside of mealtimes on SB. It really has been a journey of self-control for me, and I can't imagine going back to the old me.
As for exercise, I had no issues on P1, but I am by no means a marathoner or a hard-core exerciser... but 4 days a week of medium-intensity cardio and a little bit of strength training was no problem.