Many teenagers do not get enough sleep. Obesity and diabetes are increasing in teenagers as well. This study plans to learn more about sleep and insulin resistance (insulin not working) in teenagers, and how these things may be related depending on sleep. This is important to know so that the investigators understand how sleep may play a role in health conditions like extra weight gain (increased food intake and less physical activity) and diabetes. To answer this question, the investigators plan to enroll teenagers who get <7 hours of sleep on school nights and measure changes in insulin sensitivity and dietary intake after a week of typical sleep (sleeping on their normal school schedule) and a week of longer sleep (spending 1+ hour longer in bed each night).

Inclusion Criteria:

1. High school students between the age of 14-19 years
2. have typically insufficient sleep, defined by ≤ 7 hours per night on school days
3. BMI 5th-84th percentile for age and sex
4. habitually sedentary (< 3 hours of regular physical activity per week)
5. Tanner stage 4 or 5, based on breast development for girls and testicular size for boys.

Exclusion Criteria:

1. Any medications that affect IR or sleep (e.g., metformin, stimulants, atypical antipsychotics, current use of oral steroids)
2. regular use of melatonin or other sleep aids
3. a prior diagnosis of a sleep disorder (e.g. insomnia, delayed sleep phase syndrome, obstructive sleep apnea)
4. Type 2 diabetes or prediabetes
5. IQ<70 or severe mental illness that may impact sleep or ability to consent/assent (e.g., schizophrenia, psychotic episodes)
6. teens not enrolled in a traditional high school academic program (e.g., home school students)
7. schedules that would preclude participants from adhering to the sleep manipulation (e.g. night shift employment)
8. travel across more than two time zones in the 2 weeks prior to the study.