In this project we will treat 20 patients with bipolar disorder with olanzapine (a widely-used and FDA approved treatment for this condition); patients will be randomly assigned (1:1) to either standard Zyprexa tablets or orally disintegrating Zydis. We will measure symptom improvement and weight gain over the course of the study. Patients will be given dietary counseling prior to initiating either medication. In addition, we will contrast the effects of the treatments on GI-related hormones.