Inclusion Criteria:  Age: ≥ 18 years old BMI 30-50 kg/m2 Own a smartphone with Apple iOS or Android OS Baseline eating window ≥ 14 hours/day If patients are on cardiovascular medications (HMG CoA reductase inhibitors (statins), other lipid modifying drugs (including over the counter drugs such as red yeast rice and fish oil), anti-hypertensive drugs, no dose adjustments will be allowed during the study period.  Exclusion Criteria:  Taking insulin or anti-diabetic medications within the last 6 months. Manifest diabetes, defined as fasting glucose ≥ 126 mg/dL, HbA1c ≥ 6.5%, or diagnosis of diabetes. Currently taking any medication that is meant for, or has known effect on, appetite or body weight Pregnant or breast-feeding women. Caregiver for a dependent requiring frequent nocturnal care/sleep interruptions. Shift workers with variable (e.g. nocturnal) hours. Planned international travel (time zone changes) during study period. Taking therapeutic anticoagulation which might increase risk of bleeding from adipose tissue biopsy History of surgical intervention for weight loss. History of eating disorder Currently enrolled in a weight-loss or weight-management program On a special or prescribed diet for other reasons (e.g. Celiac disease) Known inflammatory and/or rheumatologic disease Active tobacco abuse or illicit drug use or history of treatment for alcohol abuse History of bone marrow or solid organ transplant History of heart failure History of major adverse cardiovascular events (acute coronary syndrome (ACS), percutaneous coronary intervention, coronary artery bypass graft surgery, stroke/transient ischemic attack (TIA)). History of atrial fibrillation or atrial flutter History of malignancy, other than non-melanoma skin cancer, that is currently being treated, or that has not been treated with definitive therapy and considered to be in remission. History of hypo- or hyperthyroidism requiring dose titration of thyroid replacement medication(s) within the past 3 months (i.e. hypothyroidism on a stable dose of thyroid replacement therapy is not an exclusion) History of adrenal disease History of cirrhosis History of stage 4 or 5 chronic kidney disease or requiring dialysis History of HIV/AIDS Uncontrolled psychiatric disorder (including history of hospitalization for psychiatric illness). History of obstructive sleep apnea (not on stable positive pressure therapy or other treatment for at least 3 months prior to enrollment) Abnormal screening labs: renal dysfunction (eGFR < 30 ml/min/1.73 m2), anemia, hypo- or hyperthyroidism, coagulopathy, abnormal liver function (AST, ALT > 3x upper limit of normal)