The purpose of this study is to test the effectiveness of two different weight loss diets on obstructive sleep apnea (OSA) severity.

Sleep apnea is a sleep disorder in which breathing repeatedly stops and starts during sleep. The most common type is obstructive sleep apnea (OSA), which occurs when the muscles in your throat relax and block your airway during sleep. The most noticeable sign of OSA is snoring. OSA is a risk factor for other chronic conditions like type 2 diabetes, cardiovascular disease, and high blood pressure.

Although anyone can develop OSA, it commonly affects people who are obese. The more someone weighs, the more likely the OSA is to be severe. Weight loss is typically recommended for overweight individuals to help improve OSA. However, not enough research has been done for doctors to be able make specific recommendations to their patients.

Inclusion Criteria:

• AHI score of ≥ 5
• Body mass index (BMI) between 30 to 49.9 kg/m2

Exclusion Criteria:

• Report serious medical risk such as insulin-dependent diabetes, active cancer, recent cardiac event
• Currently or planning to become pregnant during the next 9 months
• Not weight stable (-4.6 kg) for 3 mos. prior to intake
• Report current participation in a weight reduction program involving diet or PA
• Unwilling to be randomized to 1 of 3 study groups
• Report symptomology of an eating disorder as determined by the Eating Attitudes Test
• Unable to participate in moderate intensity physical activity