As you move up the cambridge programmes you begin to refill the stores slowly while continuing fat loss. By the end of maintenance your stores should be refilled without gain. Carbs are introduced on the 1000 plan and gradually increased as you move through.
irish eyes, i did 20 weeks SS and then went on holiday and I ate around 1500 cals from then each day. I have lost another 3.5 lbs and didn't regain weight altho I must have refilled my glycogen store...so I think maybe it's different for everyone and you don't have to gain weight...maybe you just lose a bit less than you would have?