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.

Obesity and associated metabolic conditions are a significant public health burden, costing the U.S. \~$150 billion annually. Obesity is both a disease, affecting 1 in 3 Americans, and a risk factor for other chronic diseases, such as cardiovascular disease, type 2 diabetes, and 13 forms of cancers. Diet and exercise are the cornerstone of obesity prevention and treatment. However, a considerable number of individuals are non-responsive to existing weight-loss interventions and obesity rates continue to rise. Therefore, non-conventional approaches are needed to supplement current weight-loss strategies. Daily exposure to low-oxygen conditions may aid in current weight- loss strategies. Moderate (1500-3500 m) and higher (≥ 3500 m) altitude environments are naturally hypoxic due to the lower atmospheric pressure (for reference, Denver, CO is \~1600 m and Mt. Hood in Oregon is \~3500 m). Studies show that sea-level natives exposed to moderate- or high- altitude continuously for 5 or more days lose weight, which is a consequence of prolonged reductions in blood and tissue oxygenation that lead to increased energy expenditure and decreased appetite. However, implementation of hypoxia as a means for weight loss has been limited, to date, by the logistical constraints of traveling to remote locations or access to an altitude chamber. A safe, less expensive, and more logistically feasible alternative is the use of commercially available, low-oxygen systems at sea level, which create a normobaric hypoxic environment. Whether in-home, overnight, normobaric hypoxic exposure, compared to normobaric normoxic exposure, promotes body mass loss in adults with obesity remains unknown. Furthermore, determinants of energy balance, including energy intake and expenditure, and their relative contribution to normobaric hypoxia-induced weight loss have not been investigated. 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. Chronic (8 weeks), overnight (8 hours/night) low oxygen exposure may provide a non-conventional approach to supplement current weight-loss strategies, inform new strategies to accelerate weight loss, aid long-term weight management efforts, and benefit metabolic health in individuals with obesity.

Eligibility Criteria:
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 \<42% for males, \<36% for females
* Hemoglobin \<13 g/dL for males, \<12 g/dL for females
* Blood donation within 8 weeks of beginning the study
* Present condition of alcoholism, anabolic steroids, or other substance abuse issues
* Women who are pregnant, lactating, planning to become pregnant, or who have had an irregular menstrual cycle in the past 6 mo.
* Weight gain or loss \> 10% of body weight during the past 6 months
* Adults unable to consent