I was on Depo for about 2 yrs, and went off of it because of horrible weight gain. I gained 50 pounds in 2 years, and now weigh 200 pounds. It's horrific what has happened to me. I was/am a runner, and I worked out at least 3 days a week, with cardio and some weight lifting, and kept a food journal to help me watch my calorie intake. I was doing everything right, except for being on the Depo. It was no use that I was exercising so much and eating so well....the Depo still made me gain weight like crazy!
I have been off of the Depo for almost a year now, and there is still no sign of weight loss being possible for me yet. I have read several times on the internet that it could take up to 18 months for all the hormones to leave my system and to return to normal, so it looks like both you & I may have some time to wait. My period finally came back a few months ago, though, so I'm hoping this is one good sign that my body may be on its way back to normalizing, although the period has been much lighter and shorter than it used to be. I think I'll finally know that my body is back to normal when my period returns in full force.
Good luck, and don't get too discouraged! You are not doomed to keep the weight on forever; I promise you! I refuse to believe that for myself, either. There is a fit woman inside of me, and there is one inside of you, too! It make take us a bit longer to achieve our body dreams, but we'll get there!
This discussion is related to How can I lose the weight from the Depo shot, and how long would it take?.