Publications by authors named "Holly L McClung"

21 Publications

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Effects of modern military backpack loads on walking speed and cardiometabolic responses of US Army Soldiers.

Appl Ergon 2021 Feb 27;94:103395. Epub 2021 Feb 27.

US Army Research Institute of Environmental Medicine (USARIEM), 10 General Greene Avenue, Natick, MA, 01760, USA. Electronic address:

Introduction: Military leaders must understand how modern military equipment loads affect trade-offs between movement speed and physiological strain to optimize pacing strategies.

Purpose: To evaluate the effects of load carried in a recently developed military backpack on the walking speed and cardiometabolic responses of dismounted warfighters.

Methods: Fifteen soldiers (1 woman, 14 men; age, 22 ± 2 years; height, 173 ± 7 cm; body mass (BM), 73 ± 10 kg) completed incremental walking tests with four external load conditions (0, 22, 44, or 66% BM) using the US Army's newest backpack: the Modular Lightweight Load-Carrying Equipment 4000 (MOLLE 4000). Oxygen uptake (V̇O) and heart rate (HR) were evaluated relative to maximal values (V̇O and HR respectively). Testing ceased when participants completed the highest tested speed (1.97 m s), exceeded a respiratory exchange ratio (RER) of 1.00, or reached volitional exhaustion.

Results: Peak speed significantly decreased (p < 0.03) with successively heavier loads (0% BM, 1.95 ± 0.06 m s; 22% BM, 1.87 ± 0.10 m s; 44% BM, 1.69 ± 0.13 m s; 66% BM, 1.48 ± 0.13 m s). Peak V̇O was significantly lower (p < 0.01) with 0% BM (47 ± 5% V̇O) than each load (22% BM, 58 ± 8% V̇O; 44% BM, 63 ± 10% V̇O; 66% BM, 61 ± 11% V̇O). Peak HR was significantly lower (p < 0.01) with 0% BM (71 ± 5% HR) versus each load (22% BM, 83 ± 6% HR; 44% BM, 87 ± 6% HR; 66% BM, 88 ± 6% HR).

Conclusion: Overburdened warfighters suffer severe impairments in walking speed even when carrying recently developed military load carriage equipment. Our results suggest that the relative work intensity of heavy load carriage may be better described when expressed relative to HR versus V̇O.
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http://dx.doi.org/10.1016/j.apergo.2021.103395DOI Listing
February 2021

Randomized Trial Comparing Consumption of Military Rations to Usual Intake for 21 Consecutive Days: Nutrient Adequacy and Indicators of Health Status.

J Acad Nutr Diet 2020 11 19;120(11):1791-1804. Epub 2020 Aug 19.

Background: The US military Meal, Ready-to-Eat food ration is approved as a nutritionally adequate sole source of nutrition for ≤21 days. However, the ration continuously evolves, requiring periodic reassessment of its influence on nutritional status and health.

Objective: To determine the effects of consuming the US Armed Services Meal, Ready-to-Eat ration for 21 days, relative to usual diets, on nutrient intake, and indicators of nutritional status and cardiometabolic health.

Design: Parallel-arm, randomized, controlled trial, secondary analysis.

Participants: Sixty healthy, weight stable, free-living adults from the Natick, MA, area participated between June 2015 and March 2017.

Intervention: Participants were randomized to consume their usual diet for 31days (CON), or a strictly controlled Meal, Ready-to-Eat-only diet for 21 days followed by their usual diet for 10 days (MRE).

Main Outcome Measures: Nutrient intake (absolute and adjusted) throughout the study period, and indicators of nutrition status (vitamins B, D, folate, homocysteine, iron, magnesium, and zinc) and cardiometabolic health (glucose, insulin, and blood lipid levels) before (Day 0), during (Day 10 through Day 21), and after (Day 31) the intervention period.

Statistical Analysis Performed: Between-group differences over time were assessed using marginal models. Models for nutritional status and cardiometabolic health indicators were adjusted for age, initial body mass index, and baseline value of the dependent variable.

Results: Energy-adjusted fiber; polyunsaturated fatty acids; vitamins A, thiamin, riboflavin, B-6, C, D, and E; and magnesium and zinc intakes all increased in MRE during the intervention and were higher compared with CON (P<0.05), whereas relative protein intake decreased and was lower (P<0.05). Serum triglyceride concentrations averaged 19% (95% CI 0% to 41%) higher in MRE relative to CON during Days 10 to 31 (P=0.05). No statistically significant effects of diet on any other nutritional status or cardiometabolic health indicators were observed.

Conclusions: Findings demonstrate that a Meal, Ready-to-Eat ration diet can provide a more micronutrient-dense diet than usual dietary intake aiding in maintenance of nutritional status over 21 days.
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http://dx.doi.org/10.1016/j.jand.2020.06.018DOI Listing
November 2020

Sensitivity and reliability of zinc transporter and metallothionein gene expression in peripheral blood mononuclear cells as indicators of zinc status: responses to zinc exposure and habitual zinc intake in humans.

Br J Nutr 2021 Feb 23;125(4):361-368. Epub 2020 Jul 23.

Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine (USARIEM), Natick, MA 01760, USA.

Zn is an essential nutrient for humans; however, a sensitive biomarker to assess Zn status has not been identified. The objective of this study was to determine the reliability and sensitivity of Zn transporter and metallothionein (MT) genes in peripheral blood mononuclear cells (PBMCs) to Zn exposure ex vivo and to habitual Zn intake in human subjects. In study 1, human PBMCs were cultured for 24 h with 0-50 µm ZnSO4 with or without 5 µm N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), and mRNA expression of SLC30A1-10, SLC39A1-14, MT1 subtypes (A, B, E, F, G, H, L, M and X), MT2A, MT3 and MT4 mRNA was determined. In study 2, fifty-four healthy male and female volunteers (31·9 (sd 13·8) years, BMI 25·7 (sd 2·9) kg/m2) completed a FFQ, blood was collected, PBMCs were isolated and mRNA expression of selected Zn transporters and MT isoforms was determined. Study 1: MT1E, MT1F, MT1G, MT1H, MT1L, MT1M, MT1X, MT2A and SLC30A1 increased with increasing concentrations of Zn and declined with the addition of TPEN. Study 2: Average daily Zn intake was 16·0 (sd 5·3) mg/d (range: 9-31 mg/d), and plasma Zn concentrations were 15·5 (SD 2·8) μmol/l (range 11-23 μmol/l). PBMC MT2A was positively correlated with dietary Zn intake (r 0·306, P = 0·03) and total Zn intake (r 0·382, P < 0·01), whereas plasma Zn was not (P > 0·05 for both). Findings suggest that MT2A mRNA in PBMCs reflects dietary Zn intake in healthy adults and may be a component in determining Zn status.
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http://dx.doi.org/10.1017/S0007114520002810DOI Listing
February 2021

Perspective: Guiding Principles for the Implementation of Personalized Nutrition Approaches That Benefit Health and Function.

Adv Nutr 2020 01;11(1):25-34

Health Canada, Toronto, Ontario, Canada.

Personalized nutrition (PN) approaches have been shown to help drive behavior change and positively influence health outcomes. This has led to an increase in the development of commercially available PN programs, which utilize various forms of individual-level information to provide services and products for consumers. The lack of a well-accepted definition of PN or an established set of guiding principles for the implementation of PN creates barriers for establishing credibility and efficacy. To address these points, the North American Branch of the International Life Sciences Institute convened a multidisciplinary panel. In this article, a definition for PN is proposed: "Personalized nutrition uses individual-specific information, founded in evidence-based science, to promote dietary behavior change that may result in measurable health benefits." In addition, 10 guiding principles for PN approaches are proposed: 1) define potential users and beneficiaries; 2) use validated diagnostic methods and measures; 3) maintain data quality and relevance; 4) derive data-driven recommendations from validated models and algorithms; 5) design PN studies around validated individual health or function needs and outcomes; 6) provide rigorous scientific evidence for an effect on health or function; 7) deliver user-friendly tools; 8) for healthy individuals, align with population-based recommendations; 9) communicate transparently about potential effects; and 10) protect individual data privacy and act responsibly. These principles are intended to establish a basis for responsible approaches to the evidence-based research and practice of PN and serve as an invitation for further public dialog. Several challenges were identified for PN to continue gaining acceptance, including defining the health-disease continuum, identification of biomarkers, changing regulatory landscapes, accessibility, and measuring success. Although PN approaches hold promise for public health in the future, further research is needed on the accuracy of dietary intake measurement, utilization and standardization of systems approaches, and application and communication of evidence.
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http://dx.doi.org/10.1093/advances/nmz086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7442375PMC
January 2020

A diet of U.S. military food rations alters gut microbiota composition and does not increase intestinal permeability.

J Nutr Biochem 2019 10 30;72:108217. Epub 2019 Jul 30.

Military Nutrition Division, U.S. Army Research Institute of Environmental Medicine, 10 General Greene Ave, Natick, MA 01760, USA. Electronic address:

Interactions between gut microbes and dietary components modulate intestinal permeability (IP) and inflammation. Recent studies have reported altered fecal microbiota composition together with increased IP and inflammation in individuals consuming military food rations in austere environments, but could not isolate effects of the diet from environmental factors. To determine how the U.S. Meal, Ready-to-Eat food ration affects fecal microbiota composition, IP and inflammation, 60 adults (95% male,18-61 years) were randomized to consume their usual ad libitum diet for 31 days (CON) or a strictly controlled Meal, Ready-to-Eat-only diet for 21 days followed by their usual diet for 10 days (MRE). In both groups, fecal microbiota composition was measured before, during (INT, days 1-21) and after the intervention period. IP and inflammation [high-sensitivity C-reactive protein (hsCRP)] were measured on days 0, 10, 21 and 31. Longitudinal changes in fecal microbiota composition differed between groups (P=.005), and fecal samples collected from MRE during INT were identified with 88% accuracy using random forest models. The genera making the strongest contribution to that prediction accuracy included multiple lactic acid bacteria (Lactobacillus, Lactococcus, Leuconostoc), which demonstrated lower relative abundance in MRE, and several genera known to dominate the ileal microbiota (Streptococcus, Veillonella, Clostridium), the latter two demonstrating higher relative abundance in MRE. IP and hsCRP were both lower (34% and 41%, respectively) in MRE relative to CON on day 21 (P<.05) but did not differ otherwise. Findings demonstrate that a Meal, Ready-to-Eat ration diet alters fecal microbiota composition and does not increase IP or inflammation.
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http://dx.doi.org/10.1016/j.jnutbio.2019.108217DOI Listing
October 2019

Acute stressor alters inter-species microbial competition for resistant starch-supplemented medium.

Gut Microbes 2019 22;10(4):439-446. Epub 2018 Dec 22.

a Soldier Performance and Optimization Directorate (SPOD) , U.S. Army Natick Soldier, Research, Development and Engineering Center (NSRDEC) , Natick , MA , USA.

Gut microbiome community dynamics are maintained by complex microbe-microbe and microbe-host interactions, which can be disturbed by stress. studies on the dynamics and manipulation of those interactions are costly and slow, but can be accelerated using fermentation. Herein, fermentation was used to determine how an acute stressor, a sudden change in diet, impacts inter-bacterial species competition for resistant starch-supplemented medium (RSM). Fermentation vessels were seeded with fecal samples collected from 10 individuals consuming a habitual diet or U.S. military rations for 21 days. . growth in response to RSM was attenuated following ration consumption, whereas growth of was enhanced. These differences were not evident in the pre-fermentation samples. Findings demonstrate how incorporating fermentation into clinical studies can increase understanding of stress-induced changes in nutrient-microbiome dynamics, and suggest that sudden changes in diet may impact inter-species competition for substrates.
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http://dx.doi.org/10.1080/19490976.2018.1554962DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6748575PMC
November 2019

Metabolic Costs of Standing and Walking in Healthy Military-Age Adults: A Meta-regression.

Med Sci Sports Exerc 2019 02;51(2):346-351

U.S. Army Research Institute of Environmental Medicine (USARIEM), Natick, MA.

Introduction: The Load Carriage Decision Aid (LCDA) is a U.S. Army planning tool that predicts physiological responses of soldiers during different dismounted troop scenarios. We aimed to develop an equation that calculates standing and walking metabolic rates in healthy military-age adults for the LCDA using a meta-regression.

Methods: We searched for studies that measured the energetic cost of standing and treadmill walking in healthy men and women via indirect calorimetry. We used mixed effects meta-regression to determine an optimal equation to calculate standing and walking metabolic rates as a function of walking speed (S, m·s). The optimal equation was used to determine the economical speed at which the metabolic cost per distance walked is minimized. The estimation precision of the new LCDA walking equation was compared with that of seven reference predictive equations.

Results: The meta-regression included 48 studies. The optimal equation for calculating normal standing and walking metabolic rates (W·kg) was 1.44 + 1.94S + 0.24S. The economical speed for level walking was 1.39 m·s (~ 3.1 mph). The LCDA walking equation was more precise across all walking speeds (bias ± SD, 0.01 ± 0.33 W·kg) than the reference predictive equations.

Conclusion: Practitioners can use the new LCDA walking equation to calculate energy expenditure during standing and walking at speeds <2 m·s in healthy, military-age adults. The LCDA walking equation avoids the errors estimated by other equations at lower and higher walking speeds.
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http://dx.doi.org/10.1249/MSS.0000000000001779DOI Listing
February 2019

Dietary Intake and Physical Activity Assessment: Current Tools, Techniques, and Technologies for Use in Adult Populations.

Am J Prev Med 2018 10;55(4):e93-e104

Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts.

Accurate assessment of dietary intake and physical activity is a vital component for quality research in public health, nutrition, and exercise science. However, accurate and consistent methodology for the assessment of these components remains a major challenge. Classic methods use self-report to capture dietary intake and physical activity in healthy adult populations. However, these tools, such as questionnaires or food and activity records and recalls, have been shown to underestimate energy intake and expenditure as compared with direct measures like doubly labeled water. This paper summarizes recent technological advancements, such as remote sensing devices, digital photography, and multisensor devices, which have the potential to improve the assessment of dietary intake and physical activity in free-living adults. This review will provide researchers with emerging evidence in support of these technologies, as well as a quick reference for selecting the "right-sized" assessment method based on study design, target population, outcome variables of interest, and economic and time considerations.

Theme Information: This article is part of a theme issue entitled Innovative Tools for Assessing Diet and Physical Activity for Health Promotion, which is sponsored by the North American branch of the International Life Sciences Institute.
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http://dx.doi.org/10.1016/j.amepre.2018.06.011DOI Listing
October 2018

Ingesting a Combined Carbohydrate and Essential Amino Acid Supplement Compared to a Non-Nutritive Placebo Blunts Mitochondrial Biogenesis-Related Gene Expression after Aerobic Exercise.

Curr Dev Nutr 2017 Jun 23;1(6):e000893. Epub 2017 May 23.

Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA.

Whether load carriage (LC), an endurance exercise mode composed of the aerobic component of traditional endurance exercise [e.g., cycle ergometry (CE)] and contractile forces characteristic of resistive-type exercise, modulates acute mitochondrial adaptive responses to endurance exercise and supplemental nutrition [carbohydrate + essential amino acids (CHO+EAA)] is not known. The aim of this study was to examine the effects of LC and CE, with or without CHO+EAA supplementation, on acute markers of mitochondrial biogenesis. Twenty-five adults performed 90 min of metabolically matched LC (treadmill walking, wearing a vest equal to 30% of body mass) or CE exercise during which CHO+EAA (46 g carbohydrate and 10 g essential amino acids) or non-nutritive control (CON) drinks were consumed. Muscle biopsy samples were collected at rest (pre-exercise), post-exercise, and after 3 h of recovery to assess citrate synthase activity and the expression of mRNA (reverse transcriptase-quantitative polymerase chain reaction) and protein (Western blot). Citrate synthase and phosphorylated p38 mitogen-activated protein kinase (p38 MAPK) were elevated postexercise compared with pre-exercise (time main effect, < 0.05). Peroxisome proliferator-activated γ-receptor coactivator 1α () expression was highest after recovery for CE compared with LC (exercise-by-time effect, < 0.05). Sirtuin 1 () expression postexercise was higher for CON than for CHO+EAA treatments (drink-by-time, < 0.05). Tumor suppressor p53 (), mitochondrial transcription factor A (), and cytochrome c oxidase subunit IV () expression was greater for CON than for CHO+EAA treatments (drink main effect, < 0.05). and expressions were positively associated ( < 0.05) with ( = 0.629 and 0.736, respectively) and ( = 0.465 and 0.461, respectively) expressions. Acute mitochondrial adaptive responses to endurance exercise appear to be largely driven by exogenous nutrition availability. Although CE upregulated expression to a greater extent than LC, downstream signaling was the same between modes, suggesting that LC, in large part, elicits the same acute mitochondrial response as traditional, non-weight-bearing endurance exercise. This trial was registered at clinicaltrials.gov as NCT01714479.
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http://dx.doi.org/10.3945/cdn.117.000893DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5998348PMC
June 2017

AKT2 is the predominant AKT isoform expressed in human skeletal muscle.

Physiol Rep 2018 03;6(6):e13652

Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, Massachusetts.

Skeletal muscle physiology and metabolism are regulated by complex networks of intracellular signaling pathways. Among many of these pathways, the protein kinase AKT plays a prominent role. While three AKT isoforms have been identified (AKT1, AKT2, and AKT3), surprisingly little is known regarding isoform-specific expression of AKT in human skeletal muscle. To address this, we examined the expressions of each AKT isoform in muscle biopsy samples collected from the vastus lateralis of healthy male adults at rest. In muscle, AKT2 was the most highly expressed AKT transcript, exhibiting a 15.4-fold increase over AKT1 and AKT3 transcripts. Next, the abundance of AKT protein isoforms was determined using antibody immunoprecipitation followed by Liquid Chromatography-Parallel Reaction Monitoring/Mass Spectrometry. Immunoprecipitation was performed using either mouse or rabbit pan AKT antibodies that were immunoreactive with all three AKT isoforms. We found that AKT2 was the most abundant AKT isoform in human skeletal muscle (4.2-fold greater than AKT1 using the rabbit antibody and 1.6-fold greater than AKT1 using the mouse antibody). AKT3 was virtually undetectable. Next, cultured primary human myoblasts were virally-transduced with cDNAs encoding either wild-type (WT) or kinase-inactive AKT1 (AKT1-K179M) or AKT2 (AKT2-K181M) and allowed to terminally differentiate. Myotubes expressing WT-AKT1 or WT-AKT2 showed enhanced fusion compared to control myotubes, while myotubes expressing AKT1-K179M showed a 14% reduction in fusion. Myotubes expressing AKT2-K181M displayed 63% decreased fusion compared to control. Together, these data identify AKT2 as the most highly-expressed AKT isoform in human skeletal muscle and as the principal AKT isoform regulating human myoblast differentiation.
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http://dx.doi.org/10.14814/phy2.13652DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5875533PMC
March 2018

Digital food photography technology improves efficiency and feasibility of dietary intake assessments in large populations eating ad libitum in collective dining facilities.

Appetite 2017 09 17;116:389-394. Epub 2017 May 17.

U.S. Military-Baylor University Graduate Program in Nutrition, Joint Base San Antonio, TX 78234, United States.

Background: Accurate assessment of dietary intake continues to challenge researchers, especially in field, or non-laboratory settings.

Objective: In this study, digital food photography (DFP) methodology was used to assess nutritional intake (NI) of Soldiers participating in the US Army's Ranger Selection and Assessment Program (RASP).

Methods: During this high-intensity six-week course, Soldiers complete simulated operational missions, perform various military tasks, and importantly, eating time is severely limited. Therefore, this study provided an opportunity to evaluate the utility of DFP methods for accurate assessment of energy balance in conditions where consumption of large numbers of subjects must be completed in a very short periods of time (≤20 min). NI of 131 male, enlisted Soldiers (21 ± 4 years, 178±7 cm, and 78±8 kg) enrolled in the RASP course was assessed in their garrison dining facility using DFP utilizing visual estimation of pre- and post-meal photos of participant meals concurrently with photos of weighed, standardized portions. Total daily energy expenditure (TDEE) was assessed using doubly-labeled water (HO) in a sub-group of 19 volunteers.

Results: During the study, data loss (i.e., missing meal photos) was less than 5% per meal, and during the visual estimation process discrepancies in food identification averaged less than 10% per meal, while approximately a third of serving size estimations required a third party adjudication prior to finalization and calculation NI.

Conclusions: We conclude that the use of DFP allows an adequately reliable approach for quantifying NI in real-world scenarios involving large numbers of participants who must be assessed very rapidly, and researchers must have a small footprint.
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http://dx.doi.org/10.1016/j.appet.2017.05.025DOI Listing
September 2017

Skeletal Muscle myomiR Are Differentially Expressed by Endurance Exercise Mode and Combined Essential Amino Acid and Carbohydrate Supplementation.

Front Physiol 2017 23;8:182. Epub 2017 Mar 23.

Military Nutrition Division, US Army Research Institute of Environmental Medicine Natick, MA, USA.

Skeletal muscle microRNAs (myomiR) expression is modulated by exercise, however, the influence of endurance exercise mode, combined with essential amino acid and carbohydrate (EAA+CHO) supplementation are not well defined. This study determined the effects of weighted versus non-weighted endurance exercise, with or without EAA+CHO ingestion on myomiR expression and their association with muscle protein synthesis (MPS). Twenty five adults performed 90 min of metabolically-matched (2.2 VO L·m) load carriage (LC; performed on a treadmill wearing a vest equal to 30% of individual body mass) or cycle ergometry (CE) exercise, during which EAA+CHO (10 g EAA and 46 g CHO) or non-nutritive control (CON) drinks were consumed. Expression of myomiR (RT-qPCR) were determined at rest (PRE), immediately post-exercise (POST), and 3 h into recovery (REC). Muscle protein synthesis (H-phenylalanine) was measured during exercise and recovery. Relative to PRE, POST, and REC expression of miR-1-3p, miR-206, miR-208a-5, and miR-499 was lower ( < 0.05) for LC compared to CE, regardless of dietary treatment. Independent of exercise mode, miR-1-3p and miR-208a-5p expression were lower ( < 0.05) after ingesting EAA+CHO compared to CON. Expression of miR-206 was highest for CE-CON than any other treatment (exercise-by-drink, < 0.05). Common targets of differing myomiR were identified as markers within mTORC1 signaling, and miR-206 and miR-499 were inversely associated with MPS rates immediately post-exercise. These findings suggest the alterations in myomiR expression between exercise mode and EAA+CHO intake may in part be due to differing MPS modulation immediately post-exercise.
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http://dx.doi.org/10.3389/fphys.2017.00182DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5362638PMC
March 2017

Altered metabolic homeostasis is associated with appetite regulation during and following 48-h of severe energy deprivation in adults.

Metabolism 2016 Apr 6;65(4):416-27. Epub 2015 Nov 6.

Military Nutrition Division, US Army Research Institute of Environmental Medicine, 10 General Greene Ave, Bldg 42, Natick, MA 01760, USA.

Background: Military personnel frequently endure intermittent periods of severe energy deficit which can compromise health and performance. Physiologic factors contributing to underconsumption, and the subsequent drive to overeat, are not fully characterized. This study aimed to identify associations between appetite, metabolic homeostasis and endocrine responses during and following severe, short-term energy deprivation.

Methods: Twenty-three young adults (17M/6F, 21±3years, BMI 25±3kg/m(2)) participated in a randomized, controlled, crossover trial. During separate 48-h periods, participants increased habitual energy expenditure by 1647±345kcal/d (mean±SD) through prescribed exercise at 40-65% VO2peak, and consumed provided isovolumetric diets designed to maintain energy balance at the elevated energy expenditure (EB; 36±93kcal/d energy deficit) or to produce a severe energy deficit (ED; 3681±716kcal/d energy deficit). Appetite, markers of metabolic homeostasis and endocrine mediators of appetite and substrate availability were periodically measured. Ad libitum energy intake was measured over 36h following both experimental periods.

Results: Appetite increased during ED and was greater than during EB despite maintenance of diet volume (P=0.004). Ad libitum energy intake was 907kcal/36h [95% CI: 321, 1493kcal/36h, P=0.004] higher following ED compared to following EB. Serum beta-hydroxybutyrate, free fatty acids, branched-chain amino acids, dehydroepiandrosterone-sulfate (DHEA-S) and cortisol concentrations were higher (P<0.001 for all), whereas whole-body protein balance was more negative (P<0.001), and serum glucose, insulin, and leptin concentrations were lower (P<0.001 for all) during ED relative to during EB. Cortisol concentrations, but not any other hormone or metabolic substrate, were inversely associated with satiety during EB (R(2)=0.23, P=0.04). In contrast, serum glucose and DHEA-S concentrations were inversely associated with satiety during ED (R(2)=0.68, P<0.001). No associations between physiologic variables measured during EB and ad libitum energy intake following EB were observed. However, serum leptin and net protein balance measured during ED were inversely associated with ad libitum energy intake following ED (R(2)=0.48, P=0.01).

Conclusion: These findings suggest that changes in metabolic homeostasis during energy deprivation modulate appetite independent of reductions in diet volume. Following energy deprivation, physiologic signals of adipose and lean tissue loss may drive restoration of energy balance.

Clinical Trials Registration: www.clinicaltrials.gov #NCT01603550.
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http://dx.doi.org/10.1016/j.metabol.2015.11.001DOI Listing
April 2016

Human Muscle Protein Synthetic Responses during Weight-Bearing and Non-Weight-Bearing Exercise: A Comparative Study of Exercise Modes and Recovery Nutrition.

PLoS One 2015 16;10(10):e0140863. Epub 2015 Oct 16.

Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA, United States of America.

Effects of conventional endurance (CE) exercise and essential amino acid (EAA) supplementation on protein turnover are well described. Protein turnover responses to weighted endurance exercise (i.e., load carriage, LC) and EAA may differ from CE, because the mechanical forces and contractile properties of LC and CE likely differ. This study examined muscle protein synthesis (MPS) and whole-body protein turnover in response to LC and CE, with and without EAA supplementation, using stable isotope amino acid tracer infusions. Forty adults (mean ± SD, 22 ± 4 y, 80 ± 10 kg, VO 2peak 4.0 ± 0.5 L ∙ min(-1)) were randomly assigned to perform 90 min, absolute intensity-matched (2.2 ± 0.1 VO2 L ∙ m(-1)) LC (performed on a treadmill wearing a vest equal to 30% of individual body mass, mean ± SD load carried 24 ± 3 kg) or CE (cycle ergometry performed at the same absolute VO2 as LC) exercise, during which EAA (10 g EAA, 3.6 g leucine) or control (CON, non-nutritive) drinks were consumed. Mixed-muscle and myofibrillar MPS were higher during exercise for LC than CE (mode main effect, P < 0.05), independent of dietary treatment. EAA enhanced mixed-muscle and sarcoplasmic MPS during exercise, regardless of mode (drink main effect, P < 0.05). Mixed-muscle and sarcoplasmic MPS were higher in recovery for LC than CE (mode main effect, P < 0.05). No other differences or interactions (mode x drink) were observed. However, EAA attenuated whole-body protein breakdown, increased amino acid oxidation, and enhanced net protein balance in recovery compared to CON, regardless of exercise mode (P < 0.05). These data show that, although whole-body protein turnover responses to absolute VO2-matched LC and CE are the same, LC elicited a greater muscle protein synthetic response than CE.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0140863PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4608805PMC
June 2016

Energy requirements of US Army Special Operation Forces during military training.

Nutrients 2014 May 12;6(5):1945-55. Epub 2014 May 12.

Military Nutrition Division, United States Army Research Institute of Environmental Medicine, 15 Kansas Street, Building 42, Natick, MA 01760, USA.

Special Operations Forces (SOF) regularly engage in physically demanding combat operations and field training exercises, resulting in high daily energy expenditure, and thus increased energy requirements. However, the majority of studies assessing energy requirements of SOF have been conducted on soldiers going through intense SOF initiation training. The objective of the current investigation was to determine the energy expenditure of SOF conducting military training operations. Thirty-one soldiers taking part in Pre-Mission Training (PMT n = 15) and Combat Diver Qualification Courses (CDQC n = 16) volunteered to participate in this observational study. Energy expenditure was determined using doubly labeled water. Body weight (83 ± 7 kg) remained stable during both training periods. Overall energy expenditure adjusted for body composition was 17,606 ± 2326 kJ·day(-1). Energy expenditure was 19,110 ± 1468 kJ·day(-1) during CDQC and 16,334 ± 2180 kJ·day(-1) during PMT, with physical activity levels of 2.6 ± 0.2 and 2.2 ± 0.3 during CDQC and PMT, respectively. Compared to the Military Dietary Reference Intakes for energy (13,598 kJ·day(-1)), these data are in agreement with previous reports that energy requirement for SOF Soldiers exceed that of the average soldier.
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http://dx.doi.org/10.3390/nu6051945DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4042567PMC
May 2014

Effects of modified foodservice practices in military dining facilities on ad libitum nutritional intake of US army soldiers.

J Acad Nutr Diet 2013 Jul 16;113(7):920-7. Epub 2013 Feb 16.

Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.

Background: Modifying foodservice practices in military dining facilities could influence ad libitum nutritional intake patterns of soldiers.

Objective: We aimed to determine how changes in foodservice operations consistent with 2005 Dietary Guidelines for Americans affected soldiers' ad libitum nutritional intake in military dining facilities (DFACs).

Design: Ten DFACs participated, and the intervention was implemented in five DFACs in an independently sampled, partial crossover design. Nutrient intake of diners was assessed during a test meal using digital photography, and customer satisfaction with foodservice was assessed via surveys at baseline (n=602), and again at 6 months (n=519) and 12 months (n=458) after the intervention was implemented.

Participants: Volunteers were US Army active duty soldiers recruited from among diners at 10 DFACs on Fort Bragg, NC.

Main Outcome Measures: Primary outcomes were intakes of energy and total fat, and percent energy from fat and saturated fat. Differences between diners' intakes in control and intervention DFACs were assessed using independent samples t tests.

Results: At 6 months after implementing the intervention, diners at intervention DFACs had significantly lower lunchtime intakes of energy (945±338 kcal vs 1,061±380 kcal), total fat (38±19 g vs 47±25 g), percent energy from fat (35%±10% vs 39%±11%) and saturated fat (4.7%±1.7% vs 5.6%±2.3%), discretionary fat (30±18 g vs 39±24 g), and refined grains (2.3±1.7 oz equivalents vs 2.8±2.4 oz equivalents) compared with diners at control DFACs. Further, diners at intervention DFACs rated customer satisfaction higher than diners at control DFACs.

Conclusions: These findings suggest that modest changes in military DFAC serving practices to promote healthy eating and food selection can facilitate positive changes in soldiers' nutritional intake.
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http://dx.doi.org/10.1016/j.jand.2013.01.005DOI Listing
July 2013

Effects of short-term quercetin supplementation on soldier performance.

J Strength Cond Res 2012 Jul;26 Suppl 2:S53-60

Military Performance Division, USARIEM, Natick, Massachusetts, USA.

The purpose was to assess the short-term effects of quercetin supplementation on aerobically demanding soldier performance. In a double-blind crossover study, 16 male soldiers performed 3 days of aerobically demanding exercise under 3 conditions: Baseline (B), Placebo (P), and Quercetin (Q). Day 1 was a treadmill V[Combining Dot Above]O₂peak test. Days 2 and 3 were identical, consisting of 75 minutes of loaded treadmill marching (LM) and a subsequent cycling time trial (TT) to complete 200 kJ of work. After B condition, the soldiers consumed 2 energy bars, each containing 0 mg (placebo) or 500 mg of quercetin (1,000 mg·d⁻¹) for 8.5 days. Beginning day 6 of supplementation, the soldiers performed the 3 exercise days. There was a significant (p < 0.05) increase in plasma Q after Q supplementation. Repeated measures analyses of variance revealed no differences after P or Q supplementation as compared with B in V[Combining Dot Above]O₂peak (B = 48.9 ± 1.1, P = 49.3 ± 1.1, Q = 48.8 ± 1.2 ml·kg⁻¹·min⁻¹) or TT time (B = 18.4 ± 1.0, P = 18.5 ± 1.1, Q = 18.3 ± 1.0 minutes [mean day 1 and day 2]). The respiratory exchange ratio during LM did not differ across treatments (B = 0.87 ± 0.03, P = 0.87 ± 0.03, Q = 0.86 ± 0.04 [mean day 1 and day 2]). Ratings of perceived exertion were not affected by Q supplementation during the V[Combining Dot Above]O₂peak test, LM or TT. Supplementation of 1,000 mg·d⁻¹ of quercetin for 8.5 days had no positive effect on aerobically demanding soldier performance. It is possible that a different dosing regimen, a combination of antioxidants or a different form of quercetin supplementation, may be needed to produce an increase in soldier performance.
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http://dx.doi.org/10.1519/JSC.0b013e31825cf22dDOI Listing
July 2012

Leucine-enriched essential amino acid supplementation during moderate steady state exercise enhances postexercise muscle protein synthesis.

Am J Clin Nutr 2011 Sep 20;94(3):809-18. Epub 2011 Jul 20.

Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA, USA.

Background: The effects of essential amino acid (EAA) supplementation during moderate steady state (ie, endurance) exercise on postexercise skeletal muscle metabolism are not well described, and the potential role of supplemental leucine on muscle protein synthesis (MPS) and associated molecular responses remains to be elucidated.

Objective: This randomized crossover study examined whether EAA supplementation with 2 different concentrations of leucine affected post-steady state exercise MPS, whole-body protein turnover, and mammalian target of rapamycin 1 (mTORC1) intracellular signaling.

Design: Eight adults completed 2 separate bouts of cycle ergometry [60 min, 60% VO(2)peak (peak oxygen uptake)]. Isonitrogenous (10 g EAA) drinks with different leucine contents [leucine-enriched (l)-EAA, 3.5 g leucine; EAA, 1.87 g leucine] were consumed during exercise. MPS and whole-body protein turnover were determined by using primed continuous infusions of [(2)H(5)]phenylalanine and [1-(13)C]leucine. Multiplex and immunoblot analyses were used to quantify mTORC1 signaling.

Results: MPS was 33% greater (P < 0.05) after consumption of L-EAA (0.08 ± 0.01%/h) than after consumption of EAA (0.06 ± 0.01%/h). Whole-body protein breakdown and synthesis were lower (P < 0.05) and oxidation was greater (P < 0.05) after consumption of L-EAA than after consumption of EAA. Regardless of dietary treatment, multiplex analysis indicated that Akt and mammalian target of rapamycin phosphorylation were increased (P < 0.05) 30 min after exercise. Immunoblot analysis indicated that phosphorylation of ribosomal protein S6 and extracellular-signal regulated protein kinase increased (P < 0.05) and phosphorylation of eukaryotic elongation factor 2 decreased (P < 0.05) after exercise but was not affected by dietary treatment.

Conclusion: These findings suggest that increasing the concentration of leucine in an EAA supplement consumed during steady state exercise elicits a greater MPS response during recovery. This trial is registered at clinicaltrials.gov as NCT01366924.
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http://dx.doi.org/10.3945/ajcn.111.017061DOI Listing
September 2011

Molecular responses to moderate endurance exercise in skeletal muscle.

Int J Sport Nutr Exerc Metab 2010 Aug;20(4):282-90

Military Nutrition Div., U.S. Army Research Institute of Environmental Medicine, Natick, MA, USA.

This study examined alterations in skeletal-muscle growth and atrophy-related molecular events after a single bout of moderate-intensity endurance exercise. Muscle biopsies were obtained from 10 men (23 ± 1 yr, body mass 80 ± 2 kg, and VO(2peak) 45 ± 1 ml x kg⁻¹ x min⁻¹) immediately (0 hr) and 3 hr after a 60-min bout of cycle exercise (60% +/- 5% VO(2peak)). Corresponding muscle biopsies were also obtained under resting conditions. The phosphorylation status of insulin/IGF-PI3K molecular-signaling proteins, ubiquitin-proteasome-related gene expression, FOXO transcription factors, and myogenic regulatory factors in muscle samples was analyzed using multiplex analysis, Western blotting, and quantitative real-time polymerase chain reaction (qRT-PCR). A condition-time interaction was observed for Akt phosphorylation (p < .05) with multiplexing. Regardless of endurance exercise, Akt phosphorylation decreased and ERK phosphorylation increased at 3 hr compared with 0 hr (p < .05). Levels of p70(S6K) phosphorylation were 110% greater (p < .05) at 3 hr than at 0 hr using Western blots. MuRF mRNA expression postexercise increased; levels were 4.7- and 5.7-fold greater (p < .05) at 0 hr and 3 hr, respectively, than at rest with qRT-PCR. Atrogin mRNA expression was up-regulated 3.2-fold 3 hr postexercise compared with rest. These findings demonstrate modest changes in the molecular responses to moderate endurance exercise in the absence of nutrition. This study provides the groundwork for future investigations designed to optimize the metabolic conditions necessary to positively influence the cellular mechanisms specific to skeletal-muscle protein turnover during recovery from endurance exercise.
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http://dx.doi.org/10.1123/ijsnem.20.4.282DOI Listing
August 2010

Monitoring energy intake: a hand-held personal digital assistant provides accuracy comparable to written records.

J Am Diet Assoc 2009 Jul;109(7):1241-5

Military Nutrition Division, US Army Research Institute of Environmental Medicine, Natick, MA 01760, USA.

New approaches to assess energy intake (EI) may have advantages over traditional written methods, but validity of these emerging methodologies must be demonstrated. This exploratory study compared EI obtained using a hand-held personal digital assistant (PDA) and traditional written records with total energy expenditure measured by doubly labeled water (TEE(DLW)). Twenty-six volunteers (aged 23+/-4 years, body mass index [calculated as kg/m(2)] 24+/-2) participated in a randomized (either PDA or written record group) and matched (for sex, age, and body mass index) study for 7 consecutive days between June 2005 and April 2006 to record EI. Group comparisons were made with t and Mann-Whitney U tests. Bland-Altman plots were used to compare limits of agreement between methods. Volunteers remained weight stable during the study period (0.2+/-0.8 kg; P>0.05). Reported EI by written record and PDA were similar to TEE(DLW); 105% vs 92% of TEE(DLW), respectively (P>0.05). There was a significant relationship between reported EI by PDA and TEE(DLW) (r=0.60, P<0.05), but not for written record (r=0.45, P>0.05). Limits of agreement indicated both written record and PDA had large variability (range 1,394 to -1,472 kcal/day). Findings suggest the bias in using a PDA is similar to that observed when using a written record for estimation of EI in weight-stable volunteers.
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http://dx.doi.org/10.1016/j.jada.2009.04.015DOI Listing
July 2009