I have been on heaps of meds and none of them made me gain weight until I was put on Lithium. I went from being 45kg (underweight) to over 60kg in a few months. I wasn't eating any more than usual or exercising any less. Because of this I have tried to go off Lithium a couple of times but my symptoms return. Lithium has been a godsend for me in treating irritability, impulsiveness, agitation and most importantly reducing my suicidal urges. So I will keep the weight gain and have my sanity. Still I am careful to eat relatively well and take exercise. It is good for my overall health too.