Sleep is an important factor for overall health. This study will see how different light exposure patterns and food intake impact a person's metabolism (how the body breaks down food) when sleeping is reduced.

Participants will attend 6 to 8 in-person visits to the study clinic, including three overnight stays. People will complete surveys and medical tests. The study will last about 4 to 6 months.

This study is a randomized in-lab, cross-over trial. Each participant will complete all three arms in either condition order #1 (A-B-C) or order #2 (A-C-B). Each arm will consist of 5 nights of experimental sleep restriction followed by a constant routine protocol for assessment of 24-h rhythms. Sleep restriction in the three arms will occur under the following conditions: (A-control condition) Sleep Restriction with Central and Peripheral Alignment; (B) Sleep Restriction with Central Clock Misalignment; and (C) Sleep Restriction with Peripheral Misalignment. Prior to enrollment participants will complete a comprehensive medical history and clinical overnight sleep disorders screening. Baseline consists of a ~2-week ambulatory real-world monitoring segment that will occur immediately prior to each in-lab sleep restriction condition. Following the 5 days of sleep restriction in each arm, participants will complete an intravenous glucose tolerance test to analyze insulin sensitivity, prior to completing the constant routine.

Inclusion Criteria:

1. Age: 18-35 years old; equal numbers of men and women
2. Body Mass Index (BMI): 18.5-24.9 kg/m2
3. Sleep Habits: habitual self-reported average total sleep time (TST) 7-9 hours per night for prior 6 months

Exclusion Criteria:

1. Clinically diagnosed sleep disorder or apnea hypopnea index (AHI) ≥5
2. Evidence of significant organ system dysfunction or disease (e.g., heart disease, diabetes)
3. Fasting plasma glucose ≥100 mg/dL
4. Major psychiatric illness (e.g., major depressive disorder)
5. Cancer that has been in remission less than 5 years
6. History of shift-work in prior year
7. Weight change >5% of body weight over prior six months
8. Currently following a weight-loss program
9. Menopause
10. Pregnant/nursing
11. Greater than 5-day variation in menstrual cycle length month-to-month
12. Currently smoking
13. Alcohol intake >14 drinks/week or >3 drinks/day.
14. Use of prescription medications (except oral contraceptives) within one month prior to or during in-lab visits.
15. Consumption of illegal drugs or >500mg per day of caffeine.

Randomization to condition order will be concealed to research staff and participants until the conclusion of the condition "A", which all participants will complete first.