NCT07489690

Brief Summary

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.

Trial Health

77
On Track

Trial Health Score

Automated assessment based on enrollment pace, timeline, and geographic reach

Enrollment
8

participants targeted

Target at below P25 for not_applicable

Timeline
2mo left

Started Feb 2026

Shorter than P25 for not_applicable

Geographic Reach
1 country

1 active site

Status
recruiting

Health score is calculated from publicly available data and should be used for screening purposes only.

Trial Relationships

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Study Timeline

Key milestones and dates

Study Progress74%
Feb 2026Sep 2026

Study Start

First participant enrolled

February 14, 2026

Completed
1 month until next milestone

First Submitted

Initial submission to the registry

March 18, 2026

Completed
6 days until next milestone

First Posted

Study publicly available on registry

March 24, 2026

Completed
4 months until next milestone

Primary Completion

Last participant's last visit for primary outcome

July 15, 2026

Completed
3 months until next milestone

Study Completion

Last participant's last visit for all outcomes

September 30, 2026

Expected
Last Updated

March 24, 2026

Status Verified

February 1, 2026

Enrollment Period

5 months

First QC Date

March 18, 2026

Last Update Submit

March 18, 2026

Conditions

Cold Exposure

Keywords

endurance exercisedietary fatdietary carbohydrate

Outcome Measures

Primary Outcomes (2)

  • Endurance Performance

    2 mile time trial run

    30 minutes

  • Substrate Oxidation

    Respiratory Exchange Ratio

    90 minutes

Study Arms (2)

Higher Fat Supplement Bar

EXPERIMENTAL

Higher Fat, then High Carbohydrate

Dietary Supplement: High Fat

Higher Carbohydrate Supplement Bar

PLACEBO COMPARATOR

High Carbohydrate, then High Fat

Dietary Supplement: High Carbohydrate

Interventions

High FatDIETARY_SUPPLEMENT

Higher FatSupplement Bar

Higher Fat Supplement Bar
High CarbohydrateDIETARY_SUPPLEMENT

Higher Carbohydrate Supplement Bar

Higher Carbohydrate Supplement Bar

Eligibility Criteria

Age18 Years - 39 Years
Sexall
Healthy VolunteersYes
Age GroupsAdult (18-64)

You may qualify if:

  • 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)

You may not qualify if:

  • 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

Contact the study team to confirm eligibility.

Sponsors & Collaborators

Study Sites (1)

USARIEM

Natick, Massachusetts, 01760, United States

RECRUITING

Related Publications (1)

  • Margolis LM, Pasiakos SM. Performance nutrition for cold-weather military operations. Int J Circumpolar Health. 2023 Dec;82(1):2192392. doi: 10.1080/22423982.2023.2192392.

    PMID: 36934427BACKGROUND

MeSH Terms

Interventions

Diet, High-FatDiet, High-Protein Low-Carbohydrate

Intervention Hierarchy (Ancestors)

DietNutritional Physiological PhenomenaDiet, Food, and NutritionPhysiological PhenomenaDiet, Carbohydrate-RestrictedDiet TherapyNutrition TherapyTherapeuticsDiet, High-Protein

Central Study Contacts

USARIEM Recruitment

CONTACT

508-206-2278USARMY.USARIEM-MNDstudies@health.mil

Study Design

Study Type
interventional
Phase
not applicable
Allocation
RANDOMIZED
Masking
DOUBLE
Who Masked
PARTICIPANT, INVESTIGATOR
Masking Details
Double Blind
Purpose
TREATMENT
Intervention Model
CROSSOVER
Sponsor Type
FED
Responsible Party
SPONSOR

Study Record Dates

First Submitted

March 18, 2026

First Posted

March 24, 2026

Study Start

February 14, 2026

Primary Completion

July 15, 2026

Study Completion (Estimated)

September 30, 2026

Last Updated

March 24, 2026

Record last verified: 2026-02

Locations

US(1)