There are two ways to deal with an energy vampire. The first is to stop the vampirism from affecting you, using protective rituals and amulets. The second is to feed it energies you want to get rid of. Obesity isn't an energy -- it has many causes, and most of them these days are biological rather than psychological or energetic. (You might be surprised how many heavily marketed medicines have weight gain as a side effect.) But if you want to be rid of depression, frustration, leftover emotions from bad childhood experiences, etc., the vampire might be a good garbage disposal. No, it's not the high road, but in my experience energy vampires dislike that sort of treatment so much that they go away very quickly.