I expect u will gain if ur going from shakes and bars to actual food, if I remember right Ur meant to come off Cambridge slowly ie 2 meals shakes 1 meal food! Have u done this?
I wouldn't count that gain anyway as it's not ur weigh in day that's the only one that counts!
If u gain at weigh in then it could b cause of the switch or maybe it's ur time of the month?!
If u gain at weigh in day u may even loose it by the next week, if u follow the plan like u have been!