I don't think Celexa will make you lose weight, necessarily, but one antidepressant that has weight loss as a possible side effect is Wellbutrin.  That being said, it may not work the same way for you as everyone is different in how they react to medications.  My son is on Abilify and it has made him gain weight, but that's the trade-off to being able to function and hold down a job, which was in jeopardy before he started taking it.  This is something you should talk to your doctor about if it's a big concern for you.  Most of us don't want to gain weight if we don't have to, but sometimes we have to consider the pros and cons.  Maybe you wouldn't have to be on that particular drug for a long period of time.

Hope that helps some, but do check with your doctor.