Insufficient sleep may be one of the most common, and most preventable, obesity risk factors. The investigators wish to determine whether 14 nights of modest sleep restriction results in increased energy balance, thus potentially increasing the risk of obesity. The investigators hypothesize that sleep restriction will result in increased energy balance.

Numerous studies have reported that self-reported short sleep duration is associated with obesity and weight gain. Insufficient sleep may be one of the most common, and most preventable, obesity risk factors. Given that sleep restriction is largely voluntary and potentially correctable, understanding the mechanisms that link insufficient sleep to positive energy balance and the development of obesity, particularly visceral obesity, is crucial to clinical applications, public health policy, and informing future studies. The investigators wish to determine whether 14 nights of modest sleep restriction results in increased energy balance, thus potentially increasing the risk of obesity. The investigators will combine energy balance, biomarker, and imaging data with state-of-the art sleep monitoring to provide unambiguous data on the effects of sleep restriction on obesity. Together, the investigators findings will help explain whether the reduced sleep duration in the general population may be contributing to the current epidemic of obesity, and suggest strategies to reduce this risk.

Inclusion Criteria:

• Age 18-40 years
• BMI of 18.5-30 kg/m2
• Not a current smoker or tobacco user
• No chronic medical or psychiatric disorders
• On no prescription medications other than second generation antihistamines (cetirizine, fexofenadine, desloratadine, loratadine, etc), oral contraceptive pills, or intrauterine devices
• History of normal sleep patterns, defined as nocturnal sleep duration of 6.5-8 hours per night without regular daytime naps

Exclusion Criteria:

• The investigators will exclude subjects who have any medical or psychiatric disorders
• History of anxiety or depression
• Those taking any medications other than non-sedating antihistamines or oral contraceptives will be excluded
• Those found to have depression on a depression screening tool (BDI-II) will be excluded
• Current smokers will be excluded
• All female subjects will undergoing a screening pregnancy test and excluded if positive
• Subjects found to have significant sleep disorders will be excluded