An interventional study of Normobaric hypoxia (NH) and Normobaric normoxia (NN) in Obesity, sponsored by Pennington Biomedical Research Center. Recruiting at 1 site in United States. Open to participants aged 22 Years to 65 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-07-16.
Sponsored by Pennington Biomedical Research Center · Not applicable, Interventional, and Treatment
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.
11,522 studies on the registry are indexed under Obesity; 2,033 are open to participants now.
This study's planned enrollment of 60 is below the median of 67 across 9,006 interventional studies indexed under Obesity.
Browse Obesity studies →Pennington Biomedical Research Center is the lead sponsor of 284 studies on the registry; 31 are open to participants now.
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Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
BMI (body mass index)
Weight in kilograms divided by height in metres squared. Example: 70 kg and 1.75 m gives 70 ÷ (1.75 × 1.75) ≈ 22.9.
What counts as overweight or obesity differs between countries (some use lower cut-offs), so go by the range the study states.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
8 weeks of overnight exposure (8 hrs/night) to NH conditions (\~15% oxygen; achieved with nitrogen dilution, equivalent to \~8500 feet elevation) using a commercially available tent and generator system (Hypoxico, Inc., New York, NY).
Other: Normobaric hypoxia (NH)
8 weeks of overnight exposure (8 hrs/night) to NN conditions (\~21% oxygen; sea level) using a commercially available tent and generator system (Hypoxico, Inc., New York, NY).
Other: Normobaric normoxia (NN)
Low oxygen exposure to mimic \~8500 feet elevation (experimental).
Normal oxygen exposure to mimic sea level conditions (sham comparator).
Change in body weight
Body weight will be measured during the baseline weight maintenance phase (days -14 to 0) and each morning during the study (days 1 to 56) following an overnight fast and morning void, using a calibrated digital scale provided to participants to use at home (A\&D Medical wireless weight scale UC-352BLE, San Jose, CA). Change in body weight will be calculated as: body weight on day 56 - baseline body weight (average of days -14 to 0).
Time frame: 10 weeks (70 days)
4-compartment body composition using DEXA and deuterium dilution
Body composition will be determined following at least a 10 hour fast and morning void on day -7 and 49 using dual energy x-ray absorptiometry (DEXA, Discovery W, Hologic Inc., Bedford, MA or equivalent). The volunteer will remove all metal-containing objects from their body, lay face-up on the DEXA densitometer table in light clothing (t-shirt, shorts, socks), and be asked to remain motionless for the 8-10 min scan. A scanner emitting low energy x-rays and a detector will pass over the participant. These data will be used to calculate total body mass, fat-free mass, fat mass, and bone mass. Total body water will be measured following at least a 10 hour fast and 1 hour without water intake using oxygen-18 labeled water on days -7 and 49.
Time frame: Days -7 and 49
Waist circumference
Waist circumference will be measured to the nearest centimeter using a measuring tape. Measurements will be taken in duplicate.
Time frame: Days -7 and 49
Blood volume
Blood volume will be determined using the optimized carbon monoxide rebreathing method on days -7 and 49. In this method, a finger stick blood sample is taken and basal carboxyhemoglobin concentrations determined using a blood gas analyzer (OSM-3, Radiometer). Carbon monoxide is then inhaled via a spirometer (SpiCo, Blood Tec.) for 2 min. Seven minutes after inhaling the carbon monoxide bolus, a second finger prick blood sample is taken to determine the increase in carboxyhemoglobin concentration. The change in percentage of carboxyhemoglobin between the basal and second measurements can be used to calculate hemoglobin mass and blood volume.
Time frame: Days -7 and 49
Total daily energy expenditure (TDEE)
Energy expenditure will be assessed by the doubly labeled water (DLW) method. Briefly, upon waking, volunteers will provide a urine sample and completely void their bladder, this sample will be used to measure background isotope enrichment. The participant will then consume 1.5 g/kg of 10% O18 and 0.06 g/kg of deuterium. Urine samples will be collected at 4 h, 6.5 h, 24 h, 3 d, 5 d, and 7 d after dosing.
Time frame: Days -7 to 0 and 49-56
Resting metabolic rate
Resting metabolic rate will be measured with open circuit, indirect calorimetry (ParvoMedics TrueOne 2400 metabolic cart, Sandy, UT) in the morning, upon arrival to the lab on days 0 and 56.
Time frame: Days 0 and 56
Resting substrate oxidation
Resting substrate oxidation will be measured with open circuit, indirect calorimetry (ParvoMedics TrueOne 2400 metabolic cart, Sandy, UT) in the morning, upon arrival to the lab on days 0 and 56.
Time frame: Days 0 and 56
Ad libitum energy intake
Participants will be provided an ad libitum mixed-macronutrient meal (e.g., frozen lasagna) on days 0 and 56. Food will be provided in excess of expected consumption for one individual. Water in the amount of 240 g will be provided during the meal. Participants will be instructed to consume all water before completing the meal and will not be permitted additional water during the meal, in order to control the effect of fluid intake on satiety. To limit social influence on eating behavior, each ad libitum meal will be consumed in isolation. Leftover food will be collected and weighed after participants have left the laboratory. Energy and nutrient content of the amount consumed will be determined using Food Processor software (version 11.6.0, ESHA Research, Salem, OR) under the supervision of a Registered Dietitian.
Time frame: Days 0 and 56
Subjective appetite measures
Subjective appetite will be measured on study days 0 and 56. Subjectively rated appetite will be assessed immediately before the oral glucose tolerance test (OGTT), at 15, 30, 45, 60, 90, and 120 minutes after beginning the OGTT, and upon cessation of the ad libitum meal (discussed above) using 100 mm visual analog scales to rate fullness, hunger, desire to eat, and prospective food consumption. Composite satiety score will be calculated from the individual appetite scores using the equation: CSS = (fullness + (100 - Desire to eat) + (100 - Hunger) + (100 - Prospective food consumption) / 4.
Time frame: Days 0 and 56
Overnight oxygen saturation (wrist-worn device)
Participants will be provided a wrist-worn device with Bluetooth capabilities (vivosmart 4, Garmin, Olathe, KS) to be worn for 2 weeks prior to the start of the study (baseline measurement) and continuously for the entirety of the study. This devise will measure steps, physical activity levels, heart rate, overnight oxygen saturation, and sleep patterns.
Time frame: 10 weeks (70 days)
Overnight oxygen saturation (index finger pulse oximetry)
In addition to the wrist-worn physical activity monitoring device (vivosmart 4, Garmin, Olathe, KS) that will measure overnight oxygen saturation, participants also will wear a pulse oximeter (PalmSAT® 2500A) on their index finger overnight to measure oxygen saturation.
Time frame: 10 weeks (70 days)
Prevalence of acute mountain sickness
The prevalence and severity of AMS will be determined from information gathered using the shortened version of the Environmental Symptoms Questionnaire (ESQ) and the Lake Louise AMS Scoring System (LLS; 5 min; 26 questions total). At completion of the questionnaire, oxygen saturation will be determined using finger pulse oximetry (PalmSAT® 2500A, Nonin Medical, Inc., Plymouth, MN). AMS and oxygen saturation measurements will be taken in the morning (between 5:00-8:00am, inside tent) and evening (9:00pm-12:00am, inside tent) on days 0-7, 14, 21, 28, 35, 42, and 56.
Time frame: Days 0-7, 14, 21, 28, 35, 42, and 56
Heart rate variability
A 3-lead electrocardiogram will be conducted on days 0 and 56 to assess heart rate variability. Participants will have electrode patches placed on their chest to measure the electrical activity of the heart.
Time frame: Days 0 and 56
Heart rate variability
Participants will be provided a wrist-worn device with Bluetooth capabilities (vivosmart 4, Garmin, Olathe, KS) to be worn for 2 weeks prior to the start of the study (baseline measurement) and continuously for the entirety of the study. This devise will measure steps, physical activity levels, heart rate, overnight oxygen saturation, and sleep patterns.
Time frame: 10 weeks (70 days)
Urinary epinephrine
On days -1, 13, and 55 urine will be collected during the overnight time period. Participants will void their bladder before entering the tent in the evening (they will not collect this portion). Participants will collect any urine produced throughout the night and will collect one final time in the morning after exiting the tent. Epinephrine concentrations in the urine samples will be measured.
Time frame: Days -1, 13, and 55
Urinary norepinephrine
On days -1, 13, and 55 urine will be collected during the overnight time period. Participants will void their bladder before entering the tent in the evening (they will not collect this portion). Participants will collect any urine produced throughout the night and will collect one final time in the morning after exiting the tent. Norepinephrine concentrations in the urine samples will be measured.
Time frame: Days -1, 13, and 55
Urinary dopamine
On days -1, 13, and 55 urine will be collected during the overnight time period. Participants will void their bladder before entering the tent in the evening (they will not collect this portion). Participants will collect any urine produced throughout the night and will collect one final time in the morning after exiting the tent. Dopamine concentrations in the urine samples will be measured.
Time frame: Days -1, 13, and 55
Plasma glucose concentrations
A 75-g oral glucose tolerance test (OGTT) will be conducted on days 0 and 56. A venous catheter will be placed and blood samples obtained at -5, 30, 60, 90, and 120 min during the OGTT for measurements of plasma glucose and insulin concentration. Insulin sensitivity will be determined by using the whole-body insulin sensitivity index (WBISI), also known as the Matsuda Index.
Time frame: Days 0 and 56
Plasma insulin concentrations
A 75-g oral glucose tolerance test (OGTT) will be conducted on days 0 and 56. A venous catheter will be placed and blood samples obtained at -5, 30, 60, 90, and 120 min during the OGTT for measurements of plasma glucose and insulin concentration. Insulin sensitivity will be determined by using the whole-body insulin sensitivity index (WBISI), also known as the Matsuda Index.
Time frame: Days 0 and 56
Whole-body insulin sensitivity index
A 75-g oral glucose tolerance test (OGTT) will be conducted on days 0 and 56. A venous catheter will be placed and blood samples obtained at -5, 30, 60, 90, and 120 min during the OGTT for measurements of plasma glucose and insulin concentration. Insulin sensitivity will be determined by using the whole-body insulin sensitivity index (WBISI), also known as the Matsuda Index.
Time frame: Days 0 and 56
Thermic effect of glucose
The thermic effect of glucose will be measured on study days 0 and 56 with open circuit, indirect calorimetry (2400 TrueOne, Parvo Medics) using established protocols. Resting metabolic rate measurements will be taken prior to glucose administration in a thermo-neutral room while the participant is in the supine position (as described above). During the oral glucose tolerance test the thermic effect of glucose will be measured in 15 min increments for 2 hours (15-30, 45-60, 75-90, and 105-120 minutes).
Time frame: Days 0 and 56
24-hour continuous glucose concentrations
A continuous glucose monitor (Freestyle Libre Pro) will be inserted into the subcutaneous adipose tissue behind the arm and will be used to collect and assess 24-hour glucose concentrations.
Time frame: Days -14-0, 1-14, and 42-56
24-hour glucose variability
A continuous glucose monitor (Freestyle Libre Pro) will be inserted into the subcutaneous adipose tissue behind the arm and will be used to collect and assess 24-hour glucose concentrations.
Time frame: Days -14-0, 1-14, and 42-56
Assessment of sleep
Participants will be provided a wrist-worn device with Bluetooth capabilities (vivosmart 4, Garmin, Olathe, KS) to be worn for 2 weeks prior to the start of the study (baseline measurement) and continuously for the entirety of the study. This devise will measure steps, physical activity levels, heart rate, overnight oxygen saturation, and sleep patterns.
Time frame: 10 weeks (70 days)
Pittsburgh Sleep Quality Index
The Pittsburgh Sleep Quality Index will be used to examine participant sleep quality on days -1, 14, and 56 (5 min; 18 questions total).
Time frame: Days -1, 14, and 56
Subjective sleep quality
Participants will be asked to complete a sleep diary before and after sleep for 7 d at baseline, on days 0-14, and on days 49-56. The sleep diary includes questions related to mood, caffeine intake, substance use (e.g. alcohol, caffeine, and prescriptions), and sleep quality.
Time frame: Days -7-0, 1-14, and 49-56
Fasting measures of iron status
Serum iron, total iron binding capacity, soluble transferrin receptor, hepcidin, hemoglobin, hematocrit, ferritin, erythroferrone, and erythropoietin will be measured in fasting blood samples collected on days 0 and 56.
Time frame: Days 0 and 56
Psychosocial Factors
The Positive and Negative Affect Schedule (PANAS), Cohen Perceived Stress Scale, Big Five Inventory-2, Delay Discounting questionnaire, Palatable Eating Motives Scale, and the Generalized Self-Efficacy scale will be administered on day 0, 14, and 56.
Time frame: Days 0, 14, and 56
Fasting blood pressure
Participants will rest in a seated position for at least 5 minutes before an automated blood pressure cuff is used to measure blood pressure in triplicate.
Time frame: Days -7 and 49
Barrier Questionnaire
This questionnaire will be administered to participants on day 56 to assess real and perceived barriers to sleeping in a hypoxic tent (5 min; 17 questions total).
Time frame: Day 56
Change in body weight
Body weight also will be measured 4 weeks after the study intervention ends to assess whether weight loss is sustained. Change in body weight will be calculated as: * Body weight on day 84 (i.e., 4 wk post-intervention) - baseline body weight (average of days -14 to 0) * Body weight on day 84 (i.e., 4 wk post-intervention) - body weight on day 56
Time frame: 4 weeks after intervention ends
Plan to share: No
Started May 2023 (actual). Primary completion is estimated for Oct 2026, 41 months after the start.
Of 3,680 non-industry interventional studies with no phase under Obesity, half reached primary completion within 23 months of starting (the median), counting those still running; a quarter within 10 and three quarters within 43. This study's planned 41 months is above that.
Counting every sponsor, half of 3,843 studies reached it within 22 months; a quarter within 10 and three quarters within 42.
How these figures are worked out, and which studies are left out of them.
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