Objective The atypical antipsychotic drug olanzapine has been used to replace conventional (or typical) antipsychotics as a first line therapy for the treatment of schizophrenia.Olanzapine has efficacy in controlling both positive and negative symptoms with reduced extrapyramidal side effects,it however can induce significant weight gain.The mechanisms underlying this unexpected side effect remain unclear.An animal model of olanzapine induced-weight gain will promote our research to reveal these mechanisms.Purpose:In this study,we aimed to investigate (1) whether there are dose dependent effects of olanzapine treatment on food intake and body weight gain,and (2) whether there are significant effects of olanzapine treatment on blood borne hormones regulating energy balance such as peptide YY (PYY) and cholecystokinin (CCK).