Prolonged Daily Fasting as a Viable Alternative to Caloric Restriction in At-Risk Obese Humans

Inclusion Criteria: * BMI ≥30 and ≤ 55 kg/m\^2 * Own a smartphone compatible with the myCircadianClock (mCC) phone application * Self-reported habitual wakening between 5-9 am * Self reported sleep duration of 6-9 hours * Weight must be stable \[+/- 5 pounds\] for at least 3 months prior to the study * Eating window (time between 1st food intake and last food take) ≥14 hours using mCC * Insulin resistance based on HOMA-IR≥ 2.5 from screening visit results * Able to understand English Exclusion Criteria: * Use of beta-blockers or medications known to affect weight, such as thiazolidinedione (TZD), insulin, glucagon-like peptide (GLP)-1 agonists, phentermine, or sibutamine * Shift work (i.e. working from 11pm to 7am) * Clinically significant medical issues (diabetes, cardiovascular disease, uncontrolled pulmonary disease) * A history of abnormal laboratory results, such as hematologic (platelets \< 100), hepatic (LFTs \> 2X nl), renal (Cr \> 1.5) * MRI contraindication (metal in body, claustrophobia) * Eating window \< 12 hours per day * Unable to consistently document food intake using the mCC app (need at least 2 eating occasions\> 6 hours apart on a given day for at least 50% of days) * Pregnancy * Illiteracy * Concern for active eating disorder per screening questionnaire * Self-reported eating disorder or history of eating disorder