This was a concern for me too but I was able to maintain my weight without doing anything too drastic- I basically just started swimming laps once a week and quit drinking soda (eventually switched to diet soda which I can't say I recommend).
The first couple weeks my sugar cravings were out of control and I was eating more than usual but it wasn't a permanent thing. I was already happy with my weight but have now lost 5 more pounds and feel healthier than I have maybe ever. Quitting is not easy- I relapsed for a day recently (ridiculous) but the pull of how healthy I feel now was a big factor in not actually starting again. You can do it!