Is there an anti depressant which won’t cause weight gain?

Unfortunately weight gain is a universal problem with all anti depressants. The longer one uses them, the greater the likelihood of gaining weight. So far, every anti depressant, save for bupropion (wellbutrin), has been found to cause weight gain. Even the newer SSRIs can cause profound weight gain.

Bupropion does cause an initial weight loss but this is only a transient phase and with time, one starts to regain weight. There are some anecdotal reports that effexor may not cause as much weight gain as the other antidepressants, but it can induce sleepiness. 

All patients who do take anti depressants should be advised to  change their dietary habits and enter into an exercise program if they want to prevent the weight gain.  Unfortunately, the world of depression is not easy and there is no other way out of this dilemma.