Low Oxygen Exposure and Weight Status

The objective of the proposed double-blind, parallel-arm, randomized clinical trial is to evaluate changes in body weight and composition, assess determinants of energy balance (intake and expenditure), and measure modulators of energy balance, following 8 wk of calorie restriction (-500 kcal/d) in combination with either overnight exposure to normobaric hypoxia (8 h/night, 15% FiO2, \~2640 m) or normoxia (8 h/night, 21% FiO2), using a commercially available, in-home tent system, in adults with obesity.

Inclusion Criteria: * Obese (BMI between 30-39.9 kg/m2) * Born at altitudes below 2,100 meters (\~7,000 feet) * Currently residing in Tallahassee, Florida or surrounding area * Completed a full FDA authorized or approved COVID-19 vaccination series at least 14 days before any in-person human research activity. * Not taking any medication(s) that interfere with oxygen delivery/transport for 4 weeks prior to and throughout the entire study (e.g., includes sedatives, sleeping aids, tranquilizers and/or any medication that depresses ventilation, diuretics, alpha and beta blockers). * Willing to refrain from smoking, vaping, chewing tobacco, and dietary supplement use throughout the entire study. * Willing to have a hypoxic tent set-up in their home and spend 8 consecutive hours per night in the tent for 8 weeks * Lives with a family member, partner/spouse, or roommate who can hear and respond in the unlikely event that the blood oxygen, air oxygen, or air carbon dioxide monitoring alarm would sound. Exclusion Criteria: * Living in areas that are more than 1,200 m (\~4,000 feet), or have traveled to areas that are more than 1,200 m for five days or more within the last 2 months * Individuals who have not completed a full FDA authorized or approved COVID-19 vaccination series at least 14 days before any in-person human research activity. * Cardiovascular abnormalities, gastrointestinal disorders, or any condition that interferes with oxygen delivery/transport (e.g., kidney disease, cardiovascular disease, etc.) * Oxygen saturation \< 95% while awake or oxygen saturation dips below 88% for a total of ≥ 10 min overnight in normoxic conditions * Evidence of apnea or other sleeping disorders * Evidence of prior high-altitude pulmonary edema (HAPE) or high-altitude cerebral edema (HACE) diagnosis * Diagnosis or family history of sickle cell anemia/trait * Hematocrit \