Randomized Study of Daytime vs. Delayed Eating: Effect on Weight and Metabolism

The study consists of 4 phases - screening & baseline assessment, eating condition 1, wash-out period, and eating condition 2. Before and after each phase participants will complete a 28-hour inpatient assessment at the Clinical and Translational Research Center (CTRC) of the Hospital of the University of Pennsylvania to study the impact of one's eating on body weight and fat content, metabolism, and certain markers of metabolism in the blood.

Screening In order to participate in this study the participants must undergo a complete physical examination and tests of blood and urine. These tests will determine if participants have any conditions that would prevent them from participating in the study, including diabetes or any serious uncontrolled medical condition that may interfere with their participation in the study. Other conditions that would prevent them from taking part are pregnancy or nursing, a sleep disorder, the use of certain medications, or night-shift work. A urine pregnancy test will be given to women at this screening visit.

Participants will also complete several surveys of a psychological nature and participate in a clinical interview. Sleep and exercise schedules are important and will be reviewed during their visits to see if they match with the study requirements. During the 10 days of the screening assessment, participants will keep a log in which they will record all food and beverages that they consume. They will also use these logs to record when they sleep and exercise. Their activity will be measured by a small electronic wrist activity recorder, called an Actigraph (about the size of a wrist watch), during this time. This recorder, similar to a pedometer, records all activity from the arm, and is very useful in determining if and when they get up at night. Study staff will explain how to keep this information during the baseline visit. They will return the activity recorder and log to Dr. Allison for analysis at the end of the 10-days. They are expected to return all study materials, including the Actigraph, log, and questionnaires.

Assessments Following successful completion of the screening period, they will complete the first of four assessment visits. This visit will include 28 hours (overnight) spent at the CTRC, where their meals and snacks will be provided.

They will arrive at the CTRC at the Hospital of the University of Pennsylvania at 7 am. Starting at 8 am, their blood will be drawn every four hours. A thin needle (an introducer) will be inserted into a vein in their forearm, much like an IV line. Very small blood samples, 10 mL (2 teaspoonfuls), will be collected every four hours from 8:00 am on Day 1 through 8:00 am on Day 2. From this blood study staff will measure hormones related to metabolism, sleep, and stress. They will be provided meals and snacks during this time, and they are free to watch television or use their computer or participate in other sedentary pastimes while they are there.