This study aims to determine whether abnormal bodily rhythms contribute to elevate the risk of diabetes, independently of the amount of sleep loss.

Inclusion Criteria:

• normal healthy men and women between the ages of 21 years and 39 years (inclusive) with normal weight (i.e., body mass index under 28 kg/m2 in men, 27 kg/m2 in women)
• normal findings on clinical examination, normal results on routine laboratory tests, normal EKG, normal glucose tolerance test, negative pregnancy test for women
• no personal history of psychiatric or endocrine illness
• no personal history of sleep disorder, usual total sleep time of at least 7 hours
• only female volunteers with normal ovulatory cycles will be included

Exclusion Criteria:

• subjects with irregular life habits (shiftworkers and subjects having traveled across time zones less than one month prior to the beginning of the baseline study)
• subjects taking any medication (including hormonal contraceptive therapy), and smokers are excluded
• subjects with significant sleep apnea (apnea index above 10) or significant arousal-associated periodic leg movements are excluded