I too have gain a considerable amount of weight. I have gone from 8.5 stone to almost 13 stone, I wasn't that much full term with my son. I have found nothing works. My weight really gets me down as I eat tiny portions. I've been told to eat less fruit, but lots of veg, as fruit has a lot of sugar in it. I can't exercise, although I do have an exercise bike which if I'm well enough I use. I've also bought a contraption that helps to build your core muscles which is supposed to be what we need, but I've used it once. I would be happy if I could just drop a dress size and the a lot of my gorgeous dresses would fit me.
Looking at all the replies it looks like weight gain is part of Fibro whether we like it or not.

Unfortunately, for the most part, weight gain is an almost sure thing with fibromyalgia and the medications for it. Attempts at controlling your weight can be difficult but the safest way is to eat healthy and try to exercise as much as you can, which will be limited due to the fibro pain. Quick weight loss gimmicks, i.e. pills, shakes, etc, can often make the fibro worse. Sadly, there is currently no quick fix for any of the issues related to your fibro. Please be careful that you do not make things worse by quick weight loss attempts. A few extra pounds is a lot better than make the fibro worse. Blessed Be.

Hi I am in the same boat and although the shakes like sculptress and slim fast do work, as i have ibs which I found out was part of fibro also , these just make me in so much pain, I no longer use them. Same goes for me with the tablets most have caffeine in them which is not good for you and I have had a bad reaction to most in the past. The good ones for me were raspberry ketones and green tea, I was less bloated and found i wouldn't put on weight as quickly, the other thing is though with the raspberry ketones I got bad heartburn, but that could of just been me etc.
I have joined weight watchers as I have been in the past and it has always worked, even if you don't have a lot or any weight to lose, it can help you maintain your weight. I found as my ibs has got worse over the past year I find sticking to a diet helps me greatly and I am currently losing weight which is proof it works and I feel great.
I feel guilty sometimes because I can no longer excercise only walking which I do daily so my body is used to that but anything else is a no no, as it's not worth the pain and exhaustion.
I hope you find something that works for you .

I too used to be able to do that, pre-fibro. I had gained weight from the medication (about 10 pounds). I have recently lost it, just from being sick. I have chronic nausea. I am not sure if there is a shortcut. I have tried hydroxycut but read that it is bad for you. So I stopped. Basically, I watch what I eat and when i can, I try to get some movement. I surely hope that they find a cure for this. If anyone else has some advice, i would love to hear it. I realized that I can't do workouts. Tried Jillian Michaels DVD's over the summer and it brought on a bad flare that I am still in. I don't think I can do the high intensity workouts that's for sure.

I too have gained weight from my medication and am preparing and trying Slimming World recipes. I think that, like it already been said, a lot of the weight gain is due to the Fibro and amount of medication we take!