Sleep Loss and Circadian Misalignment - Mechanisms of Insulin Resistance

Inclusion Criteria:

1. Must be between 18-45 years old.
2. Has a BMI of 18-25 kg/m2 stable weight over the previous 6 weeks.
3. Is physically and psychologically healthy (incl. regular menstrual cycles in women, no clinical disorders and/or illnesses). Women will be studied during the follicular phase of their menstrual cycle.

   Menstrual cycle criteria (using PMID 10941950) 18 to 25 years - Cycle variation ≤9 days 26 to 41 years - Cycle variation ≤7 days 42 to 45 years - Cycle variation ≤9 days
4. No current medical or drug treatment (to include steroids or hormones of any type including contraceptives), as assessed by questionnaire.
5. Has a negative pregnancy test (women), no clinically significant abnormalities in blood and urine, and free of traces of drugs.
6. No history of clinically relevant psychiatric illness.
7. No previous history of drug or alcohol abuse.
8. Not a current smoker.
9. No history of brain injury or of learning disability.
10. No previous adverse reaction to sleep deprivation, jet lag, shift work or any of the drugs to be administered.
11. Not vision or hearing impairment unless corrected back to normal.
12. No endocrine disorder (no abnormal thyroid function tests; no abnormal morning blood cortisol; no primary gonadal disease as indicated by serum LH or FSH concentration \> 10 or \> 15 IU/L, respectively; and no hyperprolactinemia indicated by prolactin \> 25 μg/L).
13. No sleep or circadian disorder.
14. Has good habitual sleep with regular bedtimes (between 6 and 10 hours in duration).
15. Not extreme morning- nor extreme evening-type using Horne-Ostberg Morningness-Eveningness criteria.
16. No travel across time zones within one month of entering the study.
17. No shift work within three months of entering the study.
18. No anemia (hematocrit \<38% in men, \<34% in women).
19. No blood donation within the previous 8 weeks.
20. No concurrent participation in another research study.