I can't say how long it will take, but can offer some tips! I was on Cymbalta for anxiety and depression and gained some weight on it. I didn't gain much because I was only on it for about 1/2 a year. About 5 pounds heavier, I started to notice the weight gain although I was eating the same as before, so I really watched what I ate. Some days I just made protein shakes with the calories I needed and drank those for 2 out of my 3 meals. I wasn't losing ANYTHING so I knew it was the antidepressants.
As soon as I went off them, I started losing weight pretty easily. Of course I had to watch what I ate and exercise. I'd recommend finding an exercise you enjoy that you can do at least 3-4 times a week. I work out 5 times a week and find that it helps with my moods and makes me feel much happier! Hopefully the same happens for you

. I chose jogging because I was tired of using the elliptical (which is what I did before) and wanted a change. I also started lifting light weights. Set aside time for exercise... it's great time for yourself to just burn off any stress. Keep around healthy foods that you enjoy and just try to eat well balanced meals! I lost the weight I gained from antidepressants within a month because I didn't gain much. I got down to my goal weight (which I haven't weighed for about 4 years) in about 5 months total. It took time, but I did allow msyelf to have a cheat day every week to eat whatever I wanted. I think it was easier to keep up the good work and maintain my goal weight when I didn't rush myself into it and did it the healthy way!