I was Told once back when I was In weight watchers that it useally takes up to three! weeks before the food you eat today will show in weight! So that being said music You should be able to tell if the pizza hurt you or not in about three weeks:). so you have three weeks to really cut back and you will be in great shape:) Don't worry about one little slip just get back on the wagon as quick as you can! I always mess up my whole day if I eat something wrong because I don't get right back on the wagon! NO I always asume that if the day has gone wrong might just as well enjoy the rest of the day:) and yes I know this is WRONG but I can't seem to help myself!!