Are you quitting cold turkey?
I have come off Nexium hated the weight gain!!! I have tried several different ppi's since giving it up ( including H2 blockers that did me no good at all) and have found that Lansoprazole (zoton) 15mg a day has been very beneficial. I have lost over 8lb and my symptoms seem to be getting better by the day, I can even eat white chocolate which I never thought I would eat again!!!!!
For me, I put weight on with most ppi's and H2 blockers when taken at a high dosage. Now, I'm only on 15mg per day I haven't had a problem with weight gain and it seems to be working okay for me.......fingers crossed.