The goal of this clinical trial is to test the impact of repeated intermittent short sleep, with short sleep maintained 5 days per week followed by 2 days of prolonged sleep, compared to daily adequate sleep, on energy balance and cardiometabolic risk. A secondary goal of this research is to determine if maintaining a constant midpoint of sleep while undergoing intermittent short sleep, leads to better outcomes than intermittent short sleep with a 2-hour delay in sleep midpoint. The aims of this research will be tested in the context of a 3-group, parallel-arm, outpatient intervention of 4 weeks in duration, in young-to-middle-aged adults (aged 18-49 years).

A large portion of the U.S. adult population reports insufficient sleep on a nightly basis. It has been shown that sustained insufficient sleep leads to adverse cardiometabolic risk profile and positive energy balance. However, sleep patterns in real life are not consistent over weeks. Individuals not obtaining sufficient sleep during the week may compensate by sleeping longer on weekends. The differences in sleep duration between week and weekend nights is approximately 1 hour, mostly due to delaying wake times rather than advancing bedtimes. A drawback of such behaviors is resultant change in sleep midpoint, which has been associated with adverse cardiometabolic health and obesity. However, very few studies have attempted to determine whether recovery sleep on weekends results in reversal of adverse health effects of insufficient sleep during the week. Available studies suggest that recovery sleep does not revert health markers to pre-sleep restriction (SR) levels. But these studies are short, usually involving only one cycle of SR followed by recovery sleep, and fail to use appropriate and robust statistical methods. Therefore, the goal of the current investigation is to evaluate the impact of repeated intermittent short sleep, with short sleep maintained 5 days/week followed by 2 days of recovery sleep, relative to daily adequate sleep, on energy balance and cardiometabolic risk markers. A secondary goal of this research is to determine if maintaining a constant sleep timing while undergoing intermittent short sleep, leads to better outcomes than intermittent short sleep in conjunction with shifts in sleep times.

Inclusion Criteria:

• Aged 18 to 49 years
• BMI 20-29.9 kg/m2
• Habitually sleeping 7-9 hours/night without sleep aids or naps

Exclusion Criteria:

• Sleep disorders
• Psychiatric disorders (including eating disorders) and seasonal affective disorder
• Pregnancy (current/prior year)
• Breastfeeding
• Smokers (Any cigarette smoking or ex-smokers <3years)
• Diabetes
• Elevated blood pressure, taking beta-blockers
• Individuals taking anti-coagulants or anti-platelets
• Recent weight change or participation in a weight loss program or have ever had bariatric surgery or other weight loss or gastrointestinal procedure.
• Travel across time zones; shift work (non-traditional hours)

Data from this study will be available for sharing with other investigators. Data sharing requests should be made in writing and sent directly to the investigator(s) who generated the data. The purposes for using shared data should be stated in the request, and the data can only be used for research purposes. Data sharing agreements should be developed and accepted by both parties before data sharing takes place. Protecting the rights and privacy of human subjects and maintaining the study participants' confidentiality will be the first priority of our data sharing plan. HIPAA privacy rule for de-identification of a dataset will be followed before transferring data.

Data will become available after results of the main aims from the final dataset have been accepted for publication.

Contact PI for information on data availability and data sharing.

Statistician will be blinded to intervention allocation; blinding of study participants is not possible due to the intervention type.