I AM Very Conerned About Gaining Weight On The Medication

I AM Very conerned about gaining weight on the medication my doctor prescibed for me. (like all anxiety medicines) I was told by my therapist and my docotor that Wellbutrin is not one that will cause weight gain, however, he prescribed the generic Bupropion which I've read most definitely puts weight on you compared to the name brand. Is this true?