I was on the depo shot for 5 years. I didn't gain any weight. after being on it for years I started having problems with my hormones. I would get very angry for no reason or even cry for no reason at all. The first 4 years was fine just not that 5th year. Once I stopped I started feeling a lot better.
I was on it for 6 months, I was bleeding/spotting everyday and gained 30+ lbs that I could not lose no matter how healthy I ate and how much I exercised. I wouldn't recommend the depo shot to anyone. I hated it.