I'm taking 20MG of Citalopram as well, I've been taking it for about a year and a half now. I had always maintained my weight prior to taking this drug, and I didn't have any weight gain at all. I have IBS as well, but my DR recently added Wellbutrin and Buspar to my Citalopram and I'm actually starting to lose weight. So, if you're maintaining your weight right now, I'm not sure it's caused by the Citalopram. Everyone reacts differently to these medications, so if you need to build your weight back, talk to your doctor or maybe increase your calorie intake.