SYNCED - SYNChronized Eating in Bipolar Depression Study

Inclusion Criteria: 1. Be 18-55 years old 2. Have a diagnosis of bipolar I or bipolar II disorder, confirmed by the Quick Structured Clinical Interview for DSM-5® Disorders, QuickSCID-5. 3. Have depression symptoms as indicated by a score of ≥12 on MADRS and ≤12 on YMRS. 4. Females of childbearing potential are willing to follow highly effective methods of contraception (mentioned below) for the duration of study\* 5. Participants must be able to speak, read, write and understand English or French. 6. Be willing and able to provide informed consent. Exclusion Criteria: 1. Have any catatonic symptoms or eating disorder(s) as measured by the Quick Structured Clinical Interview for DSM-5® Disorders, QuickSCID-5. 2. Have any unstable or inadequately treated neurological and medical conditions. 3. Have had prior bariatric surgery. 4 Be taking hypoglycemia inducing medications. 5\. Be pregnant or lactating. 6. Currently taking any stimulant medications. 7. Be participating in any other diet or weight management program for the duration of the trial. 8\. Have any contraindication to fasting as judged by the assessing clinician. 9. Recently (i.e. within the past 8 weeks) began structured psychotherapy (i.e. cognitive-behavioral therapy, interpersonal psychotherapy, family-focused therapy, or interpersonal and social rhythm therapy). 10\. Have any other medical condition, substance use disorder or suicidal ideation for which physician or investigator team expresses concern about safety or ability to participate in the study.