Effects of Varying Energy Deficits on Protein Turnover at Rest and Carbohydrate Oxidation During Steady-state Exercise

This randomized, parallel study will examine the effects of energy balance and varying magnitudes of energy deficit on 1) the protein kinetic responses to consuming high quality protein and 2) carbohydrate oxidation during steady-state exercise. Healthy adults, representative of active duty military personnel, will complete a 2 d energy balance phase followed by a randomly assigned, 5 d energy deficit phase (n=15 per group; 20%, 40% and 60% energy deficit). At the end of each energy phase the effects of energy balance and energy deficit severity on resting postabsorptive (fasting) and postprandial (after consuming ~34 g protein) muscle protein synthesis (MPS) and whole-body protein synthesis, breakdown, and balance (synthesis - breakdown) will be determined. On the next day, the effects energy balance and energy deficit severity on carbohydrate oxidation during steady-state exercise will be determined. Primary study procedures include anthropometric and body composition measures, resting metabolic rate measures, aerobic exercise, tightly controlled diet and exercise interventions, repeated blood sampling, stable isotope infusion, stable isotope ingestion, and percutaneous muscle biopsies. The following hypotheses will be tested: 1) Δ (postprandial - postabsorptive) MPS and Δ whole-body protein balance at rest will progressively decrease as magnitude of energy deficit increases and 2) exogenous carbohydrate oxidation will be higher and endogenous carbohydrate oxidation will be lower during steady-state exercise as magnitude of energy deficit increases.

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Key information

Conditions

Energy Supply; Deficiency, Severe Energy Supply; Deficiency Stress, Physiological

Age range

18 year–35 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

US Army Research Institute of Environmental Medicine

Natick, Massachusetts, 01760, United States

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

Men and women aged 18 - 35 years
Body mass index < 30.0 kg/m2
Weight stable for the past 2 months (± ~2.27 kg)
Healthy without evidence of chronic illness or musculoskeletal injury as determined by the US Army Research Institute of Environmental Medicine Office of Medical Support and Oversight (OMSO) or home duty station medical support
Routinely participate in aerobic and/or resistance exercise at least 2 days per week defined by self-report for previous 6 months
Willing to refrain from taking any nonsteroidal anti-inflammatory drugs (e.g., aspirin, Advil®, Aleve®, Naprosyn®), or any other aspirin-containing product for 10 days before the first muscle biopsy and at least 5 days after completing the last muscle biopsy
Willing to refrain from alcohol, smoking/using any nicotine product (includes e-cigarettes, vaping, chewing tobacco), caffeine, and dietary supplements during the intervention periods of the study
Supervisor approval for federal civilian employees and non-Natick Soldier Systems Center Human Research Volunteer (HRV) active duty military personnel
Females must have normal menstrual cycles between 26-32 days in duration; 5 menstrual cycles within the past 6 months; or able to provide documentation of oral/hormonal contraceptive use which contains low-dose estrogen/progesterone to maintain continuous levels throughout the 28-day cycle (i.e., no placebos)

Exclusion criteria

Metabolic or cardiovascular abnormalities, gastrointestinal disorders (e.g., kidney disease, diabetes, cardiovascular disease, etc.)
Significantly abnormal blood clotting as determined by OMSO or home duty station medical support
History of complications with lidocaine
Present condition of alcoholism, anabolic steroid use, or other substance abuse issues as determined by OMSO or home duty station medical support
Blood donation within 8-wk of beginning the study
Pregnant, trying to become pregnant, and/or breastfeeding (results of urine pregnancy test and self-report for breastfeeding will be obtained before body composition testing)
Unwilling or unable to consume study diets or foods provided due to personal preference, dietary restrictions, and/or food allergies
Unwilling or unable to adhere to study physical restrictions

Treatment and study plan

Energy Deficit

Other

A combination of individualized exercise performed on a cycle ergometer and individualized dietary prescriptions will be used to achieve energy balance or the assigned energy deficits throughout the controlled feeding and testing periods

Primary outcomes

Whole-body protein balance

Time frame: 2 days

Determined using L-[1-13C]-leucine stable isotope.
Muscle Protein Synthesis

Time frame: 2 days

Determined using L-[ring-2H5]-phenylalanine stable isotope.
Carbohydrate Oxidation during Steady-state Exercise

Time frame: 2 days

Determined using U-13C-glucose stable isotope.

Sponsors and collaborators

Lead sponsor

United States Army Research Institute of Environmental Medicine

Fed

Registry information

Important dates

Study start: 2022
Primary completion: 2024
Study completion: 2024
First posted: Jun 2, 2021
Registry last updated: Jan 21, 2026

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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