Effects of Overnight Low Oxygen Exposure on Energy Balance

Study Overview
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Brief Summary
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This research study will evaluate changes in resting metabolic rate, appetite, and heart rate variability following overnight exposure (8 h/night) to normobaric hypoxia (NH) or normobaric normoxic (NN). In randomized order, participants will sleep one night in NH conditions ( 15% oxygen; achieved with nitrogen dilution, equivalent to  8500 feet elevation) and another night in NN (control) conditions ( 20% oxygen; achieved with nitrogen dilution, equivalent to  1000 feet elevation).

Detailed Description
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Weight loss is a common factor reported in lowlanders traveling to high altitudes. Although the exact cause is unknown, studies have shown that weight loss at high altitude is associated with the amount of time and severity of the altitude exposure. Upon arrival to high altitude (≥ 5000 feet), numerous physiological adaptations occur that may promote weight loss, such as increased energy expenditure and reduced appetite. The breadth of current altitude research is limited by the logistical and monetary constraints of traveling to remote locations or access to an altitude chamber. A more logistically feasible alternative is the simulation of low oxygen conditions at sea level, using a commercially available tent and generator system to reduce ambient oxygen concentrations. The current research study will evaluate changes in resting metabolic rate, appetite, and heart rate variability following overnight exposure (8 h/night) to normobaric hypoxia (NH) or normobaric normoxic (NN). In randomized order, participants will sleep one night in NH conditions ( 15% oxygen; achieved with nitrogen dilution, equivalent to  8500 feet elevation) and another night in NN (control) conditions ( 20% oxygen; achieved with nitrogen dilution, equivalent to  1000 feet elevation). In the morning, following NH or NN exposure, resting metabolic rate will be measured using indirect calorimetry, appetite using an ad libitum buffet meal protocol, and heart rate variability by electrocardiogram. It is hypothesized that exposure to overnight NH will result in increased resting metabolic rate, decreased appetite, and decreased heart rate variability.

Official Title
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Effects of an Overnight, 8-hour Low Oxygen Exposure on Resting Energy Expenditure and Appetite: a Pilot Study

Conditions
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Resting Metabolic Rate, Appetite, Heart Rate Variability

Intervention / Treatment
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* Device: Normobaric Hypoxia
* Device: Normobaric Normoxia


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Men and women aged 20 - 45 years Body mass index between 18.5 - 24.5 kg/m2 Born at altitudes less than 2,100 meters ( 7,000 feet) Currently residing in Tallahassee, Florida or the surrounding area Not taking any medication(s) that interfere with metabolism or oxygen delivery/transport for four weeks before 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 spend two overnight visits on the Florida State University campus. 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 two months Metabolic or cardiovascular abnormalities, gastrointestinal disorders, or any condition that interferes with metabolism or oxygen delivery/transport (e.g., kidney disease, diabetes, cardiovascular disease, etc.) Prior diagnosis of apnea or other sleeping disorders Prior diagnosis of high-altitude pulmonary edema or high-altitude cerebral edema Prior diagnosis of anemia or sickle cell anemia/trait Present condition of alcoholism, anabolic steroid, 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 six months. Allergies or intolerance to foods included in the standardized or ad libitum meal (e.g., lactose intolerance/milk allergy)

Ages Eligible for Study
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Minimum Age: 20 Years
Maximum Age: 45 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Single


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Normobaric Hypoxia (NH)<br>Overnight exposure (8 hours) 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). | Device: Normobaric Hypoxia<br>* Low oxygen exposure to mimic  8500 feet elevation.<br>Device: Normobaric Normoxia<br>* Normal oxygen exposure to mimic  1000 feet elevation (sham comparator).<br>|
| Sham Comparator: Normobaric Normoxia (NN)<br>Overnight exposure (8 hours) to NN conditions ( 20% oxygen; achieved with nitrogen dilution, equivalent to  1000 feet elevation) using a commercially available tent and generator system (Hypoxico, Inc., New York, NY). | Device: Normobaric Hypoxia<br>* Low oxygen exposure to mimic  8500 feet elevation.<br>Device: Normobaric Normoxia<br>* Normal oxygen exposure to mimic  1000 feet elevation (sham comparator).<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Resting metabolic rate (kcal/d) following exposure to NH or NN conditions | Resting metabolic rate will be accessed using indirect calorimetry (TrueOne 2400, Parvo Medics, Salt Lake City, UT) following 8 hours of overnight exposure to NH or NN. | 8 hours | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Objective appetite following exposure to NH or NN conditions | Objective appetite will be assessed by measuring total energy intake during an ad libitum buffet-style meal provided to participants following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Food preferences following exposure to NH or NN conditions | Food preferences will be assessed by measuring macronutrient intake during an ad libitum buffet-style meal provided to participants following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Fasting and postprandial hunger following exposure to NH or NN conditions | Measures will be assessed before and after the ad-libitum buffet meal using visual analog scales following 8 hours of overnight exposure to NH or NN. | Hunger will be measured pre-meal (0 min), immediately post-meal, and at 15, 30, 45, 60, 90, and 120 min following 8 hours of NH or NN exposure | 
| Fasting and postprandial satiety following exposure to NH or NN conditions | Measures will be assessed before and after the ad-libitum buffet meal using visual analog scales following 8 hours of overnight exposure to NH or NN. | Satiety will be measured pre-meal (0 min), immediately post-meal, and at 15, 30, 45, 60, 90, and 120 min following 8 hours of NH or NN exposure | 
| Fasting and postprandial prospective food consumption following exposure to NH or NN conditions | Measures will be assessed before and after the ad-libitum buffet meal using visual analog scales following 8 hours of overnight exposure to NH or NN. | Prospective food consumption will be measured pre-meal (0 min), immediately post-meal, and at 15, 30, 45, 60, 90, and 120 min following 8 hours of NH or NN exposure | 
| Fasting and postprandial subjective appetite following exposure to NH or NN conditions | Measures will be assessed before and after the ad-libitum buffet meal using visual analog scales following 8 hours of overnight exposure to NH or NN. | Subjective appetite will be measured pre-meal (0 min), immediately post-meal, and at 15, 30, 45, 60, 90, and 120 min following 8 hours of NH or NN exposure | 
| Energy intake following exposure to NH or NN conditions | Energy intake will be accessed using the Automated Self-Administered 24-Hour (ASA24®) Dietary Assessment Tool to complete dietary records for 2 days following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Macronutrient intake following exposure to NH or NN conditions | Macronutrient intake will be accessed using the Automated Self-Administered 24-Hour (ASA24®) Dietary Assessment Tool to complete dietary records for 2 days following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Heart rate variability following exposure to NH or NN conditions | Heart rate variability will be measured using a 3-lead electrocardiogram following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Prevalence of acute mountain sickness following exposure to NH or NN conditions | Prevalence of acute mountain sickness will be accessed using the Environmental Symptoms Questionnaire following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Severity of acute mountain sickness following exposure to NH or NN conditions | Severity of acute mountain sickness will be accessed using the Environmental Symptoms Questionnaire following 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Continuous oxygen saturation during exposure to NH or NN | Oxygen saturation will be measured continuously using a finger pulse oximeter (PalmSAT® 2500, Nonin Medical, Inc., Plymouth, MN) during 8 hours of overnight exposure to NH or NN. | 8 hours | 
| Sleep quality following exposure to NH or NN conditions | Sleep quality will be measured by the Pittsburgh Sleep Quality Index following 8 hours of overnight exposure to NH or NN. | 8 hours | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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High altitude, Metabolic adaptations, Energy balance