Taking 900 mg. No weight gain. I had quite a lot of bloating initially (from the water drinking), but that seems to be resolving, and my body is adjusting to all the water I drink. I have noticed that I don't seem to get full when eating. I'm not sure if it's from the lithium or other meds, so I just monitor how much I eat and stop when it seems like I would have normally been full. It's hard to eat and not feel like I've eaten, but it's better than gaining weight and still want to eat.