The Effects of Treating Insomnia on Behavioral Weight Loss Outcomes in Survivors of Breast Cancer

Inclusion Criteria: * Female * 18 years of age or older * Histologically-confirmed Ductal Carcinoma In Situ (DCIS) or stage I-III invasive carcinoma of the breast * Eastern Cooperative Oncology Group (ECOG) performance status 0-2 * Current BMI ≥ 25 kg/m2 and weight ≤ 400 lbs * Willing to lose 10% of body weight * Diagnosed within 10 years with histologically-confirmed DCIS or stage I-III invasive carcinoma of the breast * Completed local therapy (i.e. surgery and radiation therapy) and any planned preoperative or adjuvant chemotherapy/immunotherapy(/HER2) human epidermal growth factor receptor 2 therapy/targeted therapy at least 3months prior to enrollment (concomitant endocrine therapy allowed) * Completed all planned/elective surgeries \>4 weeks before enrollment * Meet Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria for Insomnia disorder * Self-reported initial sleep onset time and/or wake after sleep onset (WASO) time \> 30 minutes, \> 3 nights/week * Reports sleep problems present for ≥ 3 months * Insomnia Severity Index Score ≥ 9 Exclusion Criteria: * Serious/uncontrolled medical or psychiatric condition likely to hinder participation in BWL or CBT-l (bipolar disorder, psychotic disorder, seizure disorders, autoimmune disease, etc.) * Current use of medications that cause sleep disturbances or weight gain/loss. (-) Current sedative hypnotic use * Sleep disorder other than insomnia (mild sleep apnea or moderate to severe sleep apnea successfully treated via positive airway pressure (PAP) therapy is permitted * Currently enrolled or planning to enroll in a sleep treatment or weight loss program (agree not to enroll for the duration of the study) (-) Home sleep test Apnea/hypopnea Index (AHI) \> 15 * Participants also agree not to enroll in such a program for the duration of study participation (regardless of randomization). * History of unstable psychiatric disorder * Self-reported suicidal ideation or severe depressive symptoms as determined by clinical assessment, triggered by score of ≥ 20 on the Center for Epidemiologic Studies Depression (CES-D) * Lactating, pregnant or plan to become pregnant in next 14 months * Positive urine toxicology for recreational drugs of abuse; alcohol or substance use disorder as determined by Alcohol Use Disorders Identification Test, Adapted for Use in the United States (USAUDIT294) and/or Structured Clinical Interview (SCID) * Daily smoker/nicotine user * Anything that, in the opinion of the investigator, would place the subject at increased risk or preclude the patient's full compliance with or completion of the study