 This study investigates the effects of 2 mo of continuous positive airway pressure CPAP on physical activity, energy intake EI, and cardiovascular risk factors in overweightobese patients with moderate-to-severe obstructive sleep apnea OSA and excessive daytime sleepiness EDS. Following pre-experimental baseline measures, patients will be instructed to use CPAP at home each night throughout the 2 mo treatment phase. Before and after the 2 mo treatment phase, patients will undergo a 1-d in-lab testing period at the Clinical Research Resource CRR at Columbia University Medical Center. Upon completion of the laboratory phase 1, patients will return home for a 2 mo treatment period, followed by the second tracking period including laboratory visit 2. 