Additional Study Information: We are currently looking for overweight (body mass index 25 kg/m2) men and women, age 18-65 y, to participate in a sleep study. To participate you must have been diagnosed with Obstructive Sleep Apnea within the past year, and have been prescribed continuous positive airway pressure (CPAP) but not have not yet started treatment. This is a 2-phase, inpatient study. The total duration of the study is 9 weeks, including 2 periods of 1 day spent in the laboratory. You will be asked to use a CPAP machine at home, each night for 8 weeks. We will measure your sleep, physical activity, and food intake before and after treatment. Compensation will be provided up to $500 for completing both phases.