Energy Dense Fueling for Cold-Weather Operations

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.

Study Overview

• Status: Recruiting
• Conditions: Cold Exposure
• Intervention / Treatment: Dietary supplement: High Fat; Dietary supplement: High Carbohydrate

Detailed Description

This randomized crossover double blind control 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; Climatic Chamber, Natick, MA) exposure.

The order of the treatment bar assignments will be randomized. Randomization will be created using a random numbers generator (http://randomization.com or similar). Only a designated study staff member will be unblinded to the code for the treatment bars. Volunteers will wear shorts and a t-shirt for all study procedures.

Baseline data will be collected on volunteer height, weight, body composition (dual energy x-ray absorptiometry), 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 protocol days, 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 under cold conditions, followed by a 60 min rest to induced physiological cold responses prior to the start of exercise. Volunteers will then complete 90 min of load carriage (30% body mass) steady-state (55 ± 5% V̇O2peak) treadmill exercise. 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. After steady-state exercise, aerobic performance will be assessed by having volunteers complete a 2-mile time trial. There will be a minimum washout period of 6 days.

• Study Type: Interventional
• Enrollment (Estimated): 8
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: USARIEM Recruitment; Phone Number: 508-206-2278; Email: USARMY.USARIEM-MNDstudies@health.mil

Study Locations

• United States
  • Massachusetts
    • Natick, Massachusetts, United States, 01760
      • Recruiting
      • USARIEM
      • Contact: Michael A Dawson, PhD; Phone Number: 508-206-2278; Email: USARMY.USARIEM-MNDstudies@health.mil

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

Description

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

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Higher Fat Supplement Bar; Higher Fat, then High Carbohydrate	Dietary supplement: High Fat; Higher FatSupplement Bar
Placebo Comparator: Higher Carbohydrate Supplement Bar; High Carbohydrate, then High Fat	Dietary supplement: High Carbohydrate; Higher Carbohydrate Supplement Bar

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Endurance Performance	2 mile time trial run	30 minutes
Substrate Oxidation	Respiratory Exchange Ratio	90 minutes

Collaborators and Investigators

• Sponsor: United States Army Research Institute of Environmental Medicine

Publications and helpful links

General Publications

• 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.

Study record dates

Study Major Dates

• Study Start (Actual): February 14, 2026
• Primary Completion (Estimated): July 15, 2026
• Study Completion (Estimated): September 30, 2026

Study Registration Dates

• First Submitted: March 18, 2026
• First Submitted That Met QC Criteria: March 18, 2026
• First Posted (Actual): March 24, 2026

Study Record Updates

• Last Update Posted (Actual): March 24, 2026
• Last Update Submitted That Met QC Criteria: March 18, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: dietary fat; endurance exercise; dietary carbohydrate
• Additional Relevant MeSH Terms: Therapeutics; Diet, Food, and Nutrition; Physiological Phenomena; Nutritional Physiological Phenomena; Diet Therapy; Nutrition Therapy; Diet; Diet, Carbohydrate-Restricted; Diet, High-Protein; Diet, High-Fat; Diet, High-Protein Low-Carbohydrate
• Other Study ID Numbers: 25-09H; MO240033 (Other Grant/Funding Number: MRDC)

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No