Feasibility and Acceptibility of a Multi-site Trial of Time Restircted Eating During Chemotheraply for Breast Cancer.

Inclusion Criteria:

* Age 25-99 at time of consent
* English language or Spanish language (based on availability of lab interpreters)
* ECOG 0 or 1
* Breast cancer to meet histologically confirmed Stage I-III or Stage IV with Medical Oncology approval.
* Demonstrates adequate organ function (absolute neutrophil count ≥ 1,500/μL).
* All screening labs to be obtained within 30 days prior to registration.
* Able to provide written informed consent and HIPAA authorization for release of personal health information, via an approved UIC Institutional Review Board (IRB) informed consent form and HIPAA authorization.
* Women of childbearing potential must not be pregnant or breast-feeding. A negative serum or urine pregnancy test is required per institutional practice guidelines.
* As determined at the discretion of the enrolling physician or protocol designee, ability of the subject to understand and comply with study procedures for the entire length of the study.

Exclusion Criteria:

* Women with type 1 or insulin dependent type 2 diabetes
* Women with BMI \> 45kg/m2 and \< 18.5 kg/m2
* Women who are pregnant or nursing. A negative serum or urine pregnancy test is required per institutional practice guidelines.
* Shift workers
* Women with a history of eating disorders
* Enrolled participants with a significant weight loss or weight gain within 3 months of the study (weight gain or loss \>4kg)
* Uncontrolled HIV/AIDS or active viral hepatitis
* Any prior malignancy \<5 years, chemotherapy within the last year or concurrent malignancy whose natural history or treatment has the potential to interfere with the safety or efficacy assessment of this investigational regimen, as determined by the treating medical oncologist.
* Breast cancer recurrence classified by the treating medical oncologist
* Any mental or medical condition that prevents the patient from giving informed consent or participating in the trial.
* Other major comorbidity, as determined by study PI
* Illicit drug use within previous 3 months or excessive use of alcohol (i.e., \> 2 drinks/day)
* Currently participating in Weight Watcher's or another weight loss program, including weight loss medication such as GLP-1 medications.
* Myocardial infarction
* Congestive heart failure
* Chronic hepatitis
* Cirrhosis
* Chronic pancreatitis
* History of solid organ transplantation