I have been on merina since jan 18th 2010 so 2 months now. I havent really noticed if ive gained any weight being on merina, I was on Implanon for 14 months before I got on merina so I haven't lost the weight I gained from that yet.
I had the mirena for about a year and half after I had my dd and I gained about 40 lbs although some people told me that it probably wasn't from that. I was also on zoloft for a little bit. So I'm not quite sure. Sorry I couldn't be of more help.