Remeron works very well for anxiety but it does totally cause weight gain. And until you get off of it or change medications it will be difficult for your son to lose the weight. I would definitely try another medication there are enough out there that may work just as well and not cause weight gain. Sometimes the antidepressants can help with anxiety. Like Wellbutrin has been know to treat both anxiety and depression. There is little weight gain with this medication. Just like everything though I would definitely do what you are doing and ask a mental health professional, they may know of just the right med for you. Good for you for looking for an alternative.