Inclusion Criteria:

• * Overweight or obese (BMI 25.5- 34.9 kg/m2) men and women
• * Ages 18 to 40 years
• * Weight stable (no change \>25 lbs in the past 3 months)
• * Owns a smartphone and willing to install the study app

Exclusion Criteria:

• * Presence of obstructive sleep apnea or history of any other sleep disorder.
• * Irregular menses, menopausal symptoms or post-menopausal, currently pregnant, trying to get pregnant or nursing
• * Regular travel across time zones
• * Subjects who are currently following a weight loss regimen or any other special diet or exercise programs
• * Increased fractional lean body mass (e.g., athletes)
• * Unable to walk, using an assistive device for mobility, or any contraindications to exercise
• * Diabetes
• * Claustrophobia
• * Excessive alcohol (\>2 drinks/day) or caffeine (\>300mg/day) intake, regular nicotine use, substance abuse.
• * Abnormal findings on screening blood testing.
• * Participants taking any prescription, over-the-counter drugs/supplements that can affect sleep or weight.
• * Major psychiatric or any eating disorder, and any acute or chronic medical condition that increase the risk of interventions (e.g., heart disease)
• * Any underlying disease likely to limit life span and/or increase risk of interventions including cardiovascular disease (e.g. unstable angina, heart failure requiring hospitalization in the past 6 months, significant heart block or arrhythmias, NYHA Class\>2), pulmonary disease with dependence on oxygen or daily use of bronchodilators, cancer requiring treatment in the past 5 years unless the prognosis is considered good, active or chronic infection, thyroid disease and other endocrine disorders (e.g. Cushing syndrome, acromegaly), hepatitis or other chronic gastrointestinal disease (pancreatitis, inflammatory bowel disease), renal disease, significant anemia, recent surgery or significant abdominal surgery, major psychiatric or any eating disorder, acute coronary syndrome or stroke in the past 6 months