Does Meal Timing Affect Energy Expenditure

10 overweight adult men and women will eat according to two different eating schedules: grazing and time-restricting feeding ("early eating"). While on each eating schedule, metabolism (calories burned) will be measured during a 24-hour stay in a respiratory chamber. Glucose levels-as well as key diurnal rhythms such in heart rate-will also be measured continuously. This study requires two 1-week periods of participation.

Inclusion criteria

• Are 20-45 years of age
• Have a weight between 150 and 220 lbs
• Have a body mass index between 25 and 35 kg/m2 inclusive (a number calculated from your height and weight)
• If you are a female, have a regular menstrual cycle that is between 25 and 35 days long
• If you are female, had your period within the last 35 days
• Regularly go to sleep between 9:30 pm and 12:00 am
• Regularly eat dinner 9 or more hours after eating breakfast
• Are willing to have about 2/3 cup of your blood stored for future research related to this study

Exclusion criteria

• Have diabetes or are on anti-diabetes medication
• Suffer from significant cardiovascular, renal (kidney), cardiac (heart), liver, lung or nervous system disease
• Have stomach or intestinal problems
• Regularly use medications such as steroids, beta blockers, adrenergic-stimulating agents, and laxatives
• Take any medications or supplements known to affect sleep, circadian rhythms, or metabolism (with the exception that certain forms of birth control are allowed)
• Have abnormal lab work that is clinically significant in the opinion of the study physician
• Are pregnant or lactating
• Take the Depo Provera shot, or use an Interuterine Device (IUD) or hormone patch for birth control
• If you are on hormonal birth control, have been on a stable dose for less than 3 months
• Have smoked or used nicotine/tobacco products within the last 3 months
• Regularly do competitive sport training
• Perform overnight shift work an average of one or more times per week
• Have an irregular sleep schedule
• Have an irregular eating schedule
• Regularly drink 3 or more drinks of alcohol per day
• Are not able or are unwilling to eat only the food and drink served to you by Pennington Biomedical, while in the study
• Are not able or are unwilling to refrain from strenuous exercise while participating in the study
• Are not able to spend 2 separate full days (for about 25 hours each) at Pennington Biomedical
• Are not able to maintain a consistent sleep schedule while participating in the study
• Are not able to maintain a consistent eating schedule while participating in the study
• Are not able to stop drinking coffee and other caffeine-containing drinks on the day of and day prior to testing