Most, if not all, of us lose weight after cyst removal surgery. It is possible to keep it off if you eat sensibly following surgery. I don't know what exactly causes all that bloat when a cyst is present, because it's greater than the size of the cyst itself (hormones perhaps?), but usually it goes away when the cyst is removed.
I know for me, my doctor believes that my cysts may have something to do with my weight gain. I am a bigger girl. When i had the first surgery in April of last year, a laparoscopy, and they drained the cysts, in two months after surgery, i had lost 10 pounds, and i really hadnt done much. And then the pains came back, and i found that the cysts were back, and again.. that 10lbs came back on. Since surgery, this time a laparotomy, with the removal of my right ovary and tube, i have lost 5 lbs so far, without doing anything due to restrictions. Now that its been 5 weeks post op, im starting to be able to do more, and pushing my body just a little more to look at weight loss. I know it wont be easy, but me and my doctor are hoping now that the cysts are gone, i can look at losing weight. So it is very possibly that your cysts have prevented you from losing weight.
Good luck with your recovery and weight loss journey!