 Observational and epidemiological studies have found a link between obesity and short sleep duration with the prevalence of both increasing in the past decades. At this time, it is unknown whether short sleep is a cause of obesity and how short sleep would lead to obesity. Some studies associate short sleep with increased levels of hormone that stimulate appetite. This study will examine how food intake and energy expenditure can be modified by sleep duration as a means of understanding a potential causal pathway. 