Sleep Restriction and Energy Expenditure

Not Applicable

Completed

Brief Summary: Each 4-day period will follow the same protocol. Basically, for the entire study, we will prepare all of the subject's food and will require him or her to eat all of the food that we give at the times we tell them to eat. The subject will arrive at the hospital on the evening of day 1, and become inpatients. On day 2, the subject will be permitted to leave the hospital campus under the supervision of the research staff. On day 3, they will be required to stay in a small room called a metabolic chamber for 24 hours. This room measures how many calories you burn in one day. On day 4, we will measure the subject's energy expenditure in response to a breakfast meal. They will be given breakfast and the number of calories that they burn after that meal will be measured over a 6-hour period. Then the subject will be discharged at the end of the test. The 2 study periods will differ only in bedtimes and wakeup times. During one period, the subject will go to bed at 1 am and wake up at 5 am and during the other period they will go to bed at 11 pm and wake up at 7 am.

Detailed Description: Sleeping metabolic rate will be measured using a metabolic chamber on the night of day 2. During day 3, 24-hour energy expenditure (including a second night of measurement) will be measured in the metabolic chamber. On this day, the participant will perform 2 bouts of physical activity on a stationary bicycle for 15 minutes each bout. This will give us a measurement of physical activity energy expenditure. On day 4, at 7 am, the participant will exit the metabolic chamber and will enter a different, smaller metabolic chamber for the measurement of energy expenditure in response to a meal. This measurement will start at approximately 8 am with assessment of the resting metabolic rate (45 minutes). The participant will then be given a high-fat meal replacement to consume over 10 minutes. Energy expenditure measurements continue in the metabolic chamber for a 6-hour period.

Recruitment & Eligibility

Inclusion Criteria

Age 21-45 yrs
Non-pregnant, non-lactating female subjects
Body mass index (BMI) 25-28 kg/m2
Weight stable (± 2.5 kg) for at least 3 mo prior to evaluation
If a woman of child-bearing potential, must be willing to adhere to an acceptable form of contraception
Non-smoker
Regularly sleeps 7-8.5 hours/night
If taking any form of medication, other than those listed in the exclusion criteria, must have been stable and remain on the same medication and medication dose throughout the study

Exclusion Criteria

Diabetes, uncontrolled hypertension
Attempted to lose weight in past 3 months
Eating disorder
Stroke, seizure disorder, or other significant neurological disease;
HIV positive by self-report
Unstable or uncontrolled medical illness including active malignancies within past 5 yrs
Untreated or unstable hypothyroidism
Hyperthyroidism
A score on the Brief Psychiatric Inventory that exceeds the 90th percentile;
Subjects with psychoses, bipolar disorder, major depression, severe personality disorders, suicidal
Alcohol or substance abuse in the past 6 mo
Pregnant, planning pregnancy in the next 6 mo, or breast-feeding
Participating in a commercial diet or behavior modification program (e.g., Weight Watchers), or plans to participate
Shift worker, commercial long-distance driver, heavy equipment operator, history of drowsy driving
Takes naps regularly
Has traveled across time zones in the past 4 weeks or plans to during the weeks of the study
Excessive caffeine intake

Arm && Interventions

Group	Intervention	Description
Habitual Sleep	Habitual sleep	Women sleep 8 h/night throughout the study phase
Short Sleep	Short Sleep	Women sleep 4 h/night throughout the study phase

Primary Outcome Measures

Name	Time	Method
Resting Metabolic Rate	32 hours	Metabolic rate from 11 pm on day 2 until 7 am on the morning of day 4 will be measured in a metabolic chamber. The metabolic chamber is an air-tight room (22,000 l volume) equipped with a bed, chair, desk, television, VCR, telephone, treadmill, sink and toilet. All meals and snacks will be served at the scheduled time. Subjects will be asked to perform 30 min of light physical activity at 1500 h and 2030 h. Physical activity will consist of 30 min of cycling at 12 mi/h. Bedtimes will be the same as the previous night and actigraph monitoring will be used to confirm compliance with the sleep protocol. Women will exit the chamber at 0700 h the following day.

Secondary Outcome Measures

Name	Time	Method
Post Prandial Energy Expenditure and Thermic Effect of Food	8 hours on day 4	Energy expenditure will be measured from 8 am until approximately 2:30 pm on day. Resting metabolic rate over 45 minutes will be measured at 8 am, followed by breakfast and resumption of energy expenditure measurements postprandially. Participants will be given 15 min to consume a high-fat breakfast (50% of energy from fat) and post-prandial thermogenesis and substrate oxidation will be measured for the next 6 h.