NCT07489690 · United States Army Research Institute of Environmental Medicine
Energy Dense Fueling for Cold-Weather Operations
What this study is about
High daily energy expenditures without compensatory increases in energy intakes results in severe energy deficits during cold-weather military operations.
View original scientific description
High daily energy expenditures without compensatory increases in energy intakes results in severe energy deficits during cold-weather military operations. Observational and experimental data from our laboratory suggests that consuming higher-fat, energy dense products can increase energy intake and attenuate energy deficits, however, laboratory analysis is needed to understand the impact of macronutrient manipulation on substrate oxidation and aerobic performance. This proof of concept, randomized crossover study will examine the effects of consuming an isocaloric bar (approximately 350 kcal) that is higher in carbohydrate (CHO: 50% carbohydrate, 30% fat, 20% protein) or higher in fat (FAT: 30% carbohydrate, 50% fat, 20% protein) on substrate oxidation and aerobic performance (time trial) during acute cold (5°C) exposure. Volunteers will wear shorts and a t-shirt during cold exposure, with continuous monitoring of core and skin temperatures. Baseline data will be collected on volunteer height, weight, body composition, and V̇O2peak. To ensure volunteers are familiar with exercise protocols, they will complete practice sessions of all exercise before the start of data collection. Exercise and diet will be controlled throughout data collection. 24 hours prior to data collection, volunteers will consume a lead-in study diet and will abstain from exercise. After 24 hours, volunteers will return to the laboratory for assessment of substrate oxidation and aerobic performance. Volunteers will consume the CHO or FAT treatment bars under cold conditions, followed by 60 minutes of rest prior to the start of exercise. Volunteers will then complete 90 minutes of load carriage steady-state (55 ± 5% VO2peak) treadmill exercise, wearing a ruck with weighing 30% of their total body mass. After steady-state exercise, aerobic performance will be assessed by having volunteers complete a 2-mile time trial. Indirect calorimetry will be used to determine substrate oxidation during steady-state exercise. Serial blood draws will be collected during each trial to assess circulating substrate/hormone responses. Protocol days will be separated by a minimum washout period of 6 days.
Who can participate
This study lists these criteria on ClinicalTrials.gov. A study coordinator reviews eligibility during screening — this page does not determine whether you qualify.
Inclusion criteria
- • Men and women aged 18 - 39 years (17 if active Military)
- Physically active (exercise minimum 2 days per week)
- Have supervisor approval (permanent party military and civilians at NSSC)
- Willing to refrain from alcohol, nicotine products and dietary supplement use while on study diets
- Females must have normal menstrual cycles between 26-32 days in duration; 5 menstrual cycles within the past 6 months; or using oral/hormonal contraceptive which contains low-dose estrogen/progesterone to maintain continuous levels throughout the 28-day cycle (i.e., no placebos)
- Only consume caffeine products while on study diets if provided by study staff
- Body mass index (BMI) between 18.5-30 kg/m2
- In good health as determined by OMSO (Office of Medical Support and Oversight)
Exclusion criteria
- Metabolic or cardiovascular abnormalities, gastrointestinal disorders (i.e., kidney disease, diabetes, cardiovascular disease, hypertension etc.) that is unsuitable for the study determined by OMSO
- Disease or medication (i.e., diabetes medications, statins, corticosteroids, etc) that affects macronutrient utilization and/or the ability to participate in strenuous exercise
- Allergies or intolerance to foods (including but not limited to lactose intolerance/milk allergy), vegetarian practices
- Present condition of alcoholism, anabolic steroids (testosterone, enanthate, undecanoate, etc), or other substance abuse issues
- Unwilling to stop use of nutritional/sports supplements (creatine, multivitamins, whey etc.) while enrolled in the study
- Sensitivity to medical adhesives resulting in significant skin irritation
- Acute or chronic musculoskeletal injury that compromises the ability to run and ruck march
- History of disease of the gastrointestinal tract including (but not limited to) diverticulosis, diverticulitis and inflammatory bowel disease, peptic ulcer disease, Crohn's disease, ulcerative colitis; or previous gastrointestinal surgery
- Difficulty swallowing large pills or unwilling to insert rectal temperature sensor
- Raynaud's syndrome.
- History of cold injuries of any severity (e.g., frostbite, trench foot, chilblains) that puts the volunteers at increased risk for an adverse effect
- Cold-induced bronchospasms/asthma
- Blood donation within 8 weeks of the study
- Unwillingness or inability to adhere to study exercise restrictions
- Scheduled MRI within 2 weeks after completing test in cold
Where
- Natick, Massachusetts
Frequently asked questions
What is a clinical trial?
A clinical trial is a research study that tests new medical treatments, drugs, devices, or procedures to determine their safety and effectiveness. Trials are carefully designed and monitored to protect participants while advancing medical knowledge.
Is it safe to participate?
Clinical trials follow strict safety guidelines and ethical standards. Trials must be reviewed and approved, and participants are closely monitored by medical professionals throughout the study. You can withdraw at any time if you choose.
Will I be compensated?
Many clinical trials offer compensation for your time, travel expenses, and inconvenience. The specific compensation varies by study and will be discussed during the screening process. All study-related medical care is typically provided at no cost to participants.
Will I receive a placebo instead of treatment?
When effective treatment exists, participants typically receive either the standard treatment plus the study intervention, or the standard treatment plus placebo. You would not be denied effective care. Placebos are primarily used when no proven treatment is available, or in addition to standard care. Your trial consent form will clearly explain what treatments you may receive.
Can I leave a trial if I change my mind?
Absolutely. Participation in clinical trials is completely voluntary. You have the right to withdraw from the study at any time, for any reason, without penalty or loss of benefits to which you are otherwise entitled.
How long does a clinical trial last?
Trial duration varies widely depending on the study design and purpose. Some trials last just a few weeks, while others may continue for months or years. The study coordinator will provide specific timeline information during your screening call.
Data: ClinicalTrials.gov · synced Mar 24, 2026 · Source of record for eligibility and locations