Glutamic acid decarboxylase (GAD) is becoming increasingly recognised as an antigenic target in autoimmune disorders of the central nervous system. There are currently no reports of weight loss being a manifestation in such disorders. We describe two cases of anti-GAD associated neurological disorders with profound and otherwise unexplained weight loss. Both patients had incomplete response to immunotherapy, as is becoming typical of these disorders. The variable disease associations of anti-GAD antibodies is incompletely understood, and leads us to question whether weight loss in these patients could possibly be immune-mediated.