CLINICAL TRIAL / NCT02253368

Inclusion Criteria: - Age: 21-40 years - Body mass index: 25.0 to 29.9 kg/m2 - Average habitual sleep duration of 6.5 hours or less per night (as confirmed by actigraphy) - stable sleep habits for the past 6 months Exclusion Criteria: - obstructive sleep apnea or history of any other sleep disorder - night or rotating shift work (current or in the past 2 years) - habitual daytime naps - recent (< 4 week) travel across time zones - extreme chronotypes - any acute or chronic medical condition - diabetes - prior or current eating or psychiatric disorders - claustrophobia - irregular menstrual periods, menopause, pregnancy, - alcohol abuse, excessive caffeine intake, smoking, illegal drug use - subjects who are currently following a weight loss regimen or any other special diet or exercise programs - subjects who have received iv or oral contrast in the past 2 weeks - use of any prescription medication that can affect sleep or metabolism with the exception of antihypertensive and lipid lowering agents as follows. Subjects who are taking anti-hypertensive medication and/or lipid-lowering agents will be included only if they are well controlled and on a stable regimen (no change in medications in the previous 3 months). However, beta-blockers and thiazide diuretics will not be allowed, as these medications are known to affect insulin sensitivity. Women will be required to not be on hormone replacement therapy.