Andrew John Young

Andrew John Young
U.S. Army Research Institute of Environmental Medicine · Military Nutrition

About

436
Publications
107,365
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9,971
Citations
Additional affiliations
February 2014 - present
U.S. Army Research Institute of Environmental Medicine
Position
  • Scientific and Programatic Advisor
Description
  • I advise USARIEM, USARMRMC and DoD concerning Warfighter nutrition and operational physiology. I assist in research on nutritional approaches for sustaining optimal Warfighter health, resilience and performance during environmental and operational stress.

Publications

Publications (436)
Article
Context Effects of testosterone on integrated muscle protein metabolism and muscle mass during energy deficit are undetermined. Objective The objective was to determine the effects of testosterone on mixed-muscle protein synthesis (MPS), proteome-wide fractional synthesis rates (FSR), and skeletal muscle mass during energy deficit. Design This wa...
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Individuals sojourning at high altitude (≥2,500m) often develop acute mountain sickness (AMS). However, substantial unexplained inter-individual variability in AMS severity exists. Untargeted metabolomics assays are increasingly used to identify novel biomarkers of susceptibility to illness, and to elucidate biological pathways linking environmenta...
Article
Background: Lifestyle interventions are the first-line treatment for obesity, but participant weight loss is typically low. Objectives: We evaluated the efficacy of an alternative lifestyle intervention [Healthy Weight for Living (HWL)] compared with a modified Diabetes Prevention Program (m-DPP). HWL was based on a revised health behavior chang...
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Hypoxia-induced insulin resistance appears to suppress exogenous glucose oxidation during metabolically-matched aerobic exercise during acute (<8-h) high-altitude (HA) exposure. However, a better understanding of this metabolic dysregulation is needed to identify interventions to mitigate these effects. The objective of this study was to determine...
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Background: The ergogenic effects of supplemental carbohydrate on aerobic exercise performance at high altitude (HA) may be modulated by acclimatization status. Longitudinal evaluation of potential performance benefits of carbohydrate supplementation in the same volunteers before and after acclimatization to HA have not been reported. Purpose: T...
Article
Testosterone supplementation during energy deficit promotes whole-body lean mass accretion, but the mechanisms underlying that effect remain unclear. To elucidate those mechanisms, skeletal muscle molecular adaptations were assessed from muscle biopsies collected before (Resting), 1 h (Post) and 6 h (Recovery) after exercise and a mixed meal (40 g...
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Objectives Short-term energy deficit reduces acute measures of mixed muscle protein synthesis (MPS) and suppresses the hypothalamic-pituitary axis and endogenous testosterone synthesis. We hypothesized that testosterone supplementation could mitigate the effects of energy deficit on MPS. We conducted a randomized, double-blind, placebo-controlled t...
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Background: The erythropoietic cells in the bone marrow require iron to synthesize heme for incorporation into hemoglobin. Exposure to hypoxic conditions, such as extended sojourns to high altitude (HA), results in increased erythropoiesis and an increased physiological requirement for iron. In addition to increasing iron requirements, hypoxic cond...
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A recently published meta-analysis in this journal analyzed findings from studies comparing substrate use during exercise at the same relative intensity (i.e., % V̇O2max) in normoxic and hypoxic conditions. The primary conclusion was that hypoxia had no consistent effects on the contribution of carbohydrate oxidation to total energy expenditure. Ho...
Article
Background: Exogenous carbohydrate oxidation is lower during steady-state aerobic exercise in native lowlanders sojourning at high altitude (HA) compared to sea level (SL). However, the underlying mechanism contributing to reduction in exogenous carbohydrate oxidation during steady-state aerobic exercise performed at HA have not been explored. Ob...
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Background: Severe energy deficits during military operations, produced by significant increases in exercise and limited dietary intake, result in conditions that degrade lean body mass and lower-body muscle function, which may be mediated by concomitant reductions in circulating testosterone. Methods: We conducted a three-phase, proof-of-concep...
Article
Objectives Lowlanders performing steady-state aerobic exercise during high-altitude (HA) sojourns, hypoxia mediates increased endogenous carbohydrate oxidation compared to sea level (SL). At SL, ingesting carbohydrate during exercise spares endogenous carbohydrate stores and improves endurance. However, it is unclear whether that strategy is effect...
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When sea‐level (SL) residents rapidly ascend to high altitude (HA), plasma volume (PV) decreases. A quantitative model for predicting individual %∆PV over the first 7 days at HA has recently been developed from the measurements of %∆PV in 393 HA sojourners. We compared the measured %∆PV with the %∆PV predicted by the model in 17 SL natives living 2...
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Ingesting protein and carbohydrate together during aerobic exercise suppresses the expression of specific skeletal muscle microRNA and promotes muscle hypertrophy. Determining whether there are independent effects of carbohydrate and protein on microRNA will allow for a clearer understanding of the mechanistic role microRNA serve in regulating skel...
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Hypobaric hypoxia, and dietary protein and fat intakes have been independently associated with an altered gastrointestinal (GI) environment and gut microbiota, but little is known regarding host-gut microbiota interactions at high altitude (HA) and the impact of diet macronutrient composition. This study aimed to determine the effect dietary protei...
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This study investigated how high-altitude (HA, 4300 m) acclimatization affected exogenous glucose oxidation during aerobic exercise. Sea-level (SL) residents (n = 14 men) performed 80-min, metabolically matched exercise ( V ˙ O2 ∼ 1.7 L/min) at SL and at HA < 5 h after arrival (acute HA, AHA) and following 22-d of HA acclimatization (chronic HA,...
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Intramuscular factors that modulate fat-free mass (FFM) loss in lowlanders exposed to energy deficit during high-altitude (HA) sojourns remain unclear. Muscle inflammation may contribute to FFM loss at HA by inducing atrophy and inhibiting myogenesis via the tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and its receptor, fibrob...
Article
Muscle loss at high altitude (HA) is attributable to energy deficit and a potential dysregulation of anabolic signaling. Exercise and protein ingestion can attenuate the effects of energy deficit on muscle at sea level (SL). Whether these effects are observed when energy deficit occurs at HA is unknown. To address this, muscle obtained from lowland...
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Modern warfare operations often occur in volatile, uncertain, complex, and ambiguous (VUCA) environments accompanied by physical exertion, cognitive overload, sleep restriction and caloric deprivation. The increasingly fast-paced nature of these operations requires military personnel to demonstrate readiness and resiliency in the face of stressful...
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Karl, J. Philip, Renee E. Cole, Claire E. Berryman, Graham Finlayson, Patrick N. Radcliffe, Matthew T. Kominsky, Nancy E. Murphy, John W. Carbone, Jennifer C. Rood, Andrew J. Young, and Stefan M. Pasiakos. Appetite Suppression and Altered Food Preferences Coincide with Changes in Appetite-Mediating Hormones During Energy Deficit at High Altitude, B...
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In this 2-phase randomized controlled study, we examined whether consuming a higher-protein (HP) diet would attenuate fat-free mass (FFM) loss during energy deficit (ED) at high altitude (HA) in 17 healthy males (mean ± sd: 23 ± 6 yr; 82 ± 14 kg). During phase 1 at sea level (SL, 55 m), participants consumed a eucaloric diet providing standard prot...
Article
Systemic immune function is impaired by sleep restriction. However, the impact of sleep restriction on local immune responses, and to what extent any impairment can be mitigated by nutritional supplementation is unknown. We assessed the effect of 72-h sleep restriction (2-h nightly sleep) on local immune function and skin barrier restoration of an...
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Background: Cardiovascular (CV) and thermal responses to metabolically demanding multi-day military operations in extreme cold-weather environments are not well described. Characterization of these operations will provide greater insights into possible performance capabilities and cold injury risk. Methods: Soldiers from two cold-weather field t...
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Military personnel generally under-consume n-3 fatty acids and overconsume n-6 fatty acids. In a placebo-controlled, double-blinded study, we investigated whether a diet suitable for implementation in military dining facilities and civilian cafeterias could benefit n-3/n-6 fatty acid status of consumers. Three volunteer groups were provided differe...
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Background: The physiological consequences of severe energy deficit include hypogonadism and the loss of fat-free mass. Prolonged energy deficit also impacts physical performance, mood, attentiveness, and decision-making capabilities. This study will determine whether maintaining a eugonadal state during severe, sustained energy deficit attenuates...
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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:...
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Effects of environmental hypoxia on fat-free mass are well studied. Negative energy balance, increased nitrogen excretion and fat-free mass loss are commonly observed in lowlanders sojourning at high altitude. Reductions in fat-free mass can be minimized if energy consumption matches energy expenditure. However, in non-research settings, achieving...
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Individuals entering US Army service are generally young and healthy, but many are overweight, which may impact cardiometabolic risk despite physical activity and fitness requirements. This analysis examines the association between Soldiers' BMI at accession and incident cardiometabolic risk factors (CRF) using longitudinal data from 731,014 Soldie...
Data
Screening Table Weights Based on US Army Regulation 40–501. (PDF)
Data
Body Fat Percentage Standards Based on US Army Regulation 40–501. (PDF)
Data
Hazard Ratios (95% Confidence Intervals) of Strictly Defined Incident Cardiometabolic Risk Factors across Body Mass Index Categories at Accession among 731,014 US Army Entrants, 2001–2011. (PDF)
Data
ICD-9 Codes Used to Categorize Broadly- and Strictly-Defined Cardiometabolic Risk Factors and Behavioral Risk Factors. (PDF)
Data
Hazard Ratios (95% Confidence Intervals) of Broadly Defined Incident Cardiometabolic Risk Factors across Standard Table Weight Categories at Accession among 731,014 US Army Entrants, 2001–2011. (PDF)
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Short-term (5–10 days) calorie restriction (CR) downregulates muscle protein synthesis, with consumption of a high protein-based diet attenuating this decline. Benefit of increase protein intake is believed to be due to maintenance of amino acid-mediated anabolic signaling through the mechanistic target of rapamycin complex 1 (mTORC1), however, the...
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The purpose of this investigation was to assess the influence of calorie restriction (CR) alone, higher-protein/lower-carbohydrate intake alone, and combined CR higher-protein/lower-carbohydrate intake on glucose homeostasis, hepatic de novo lipogenesis (DNL), and intrahepatic triglycerides. Twelve-week old male Sprague Dawley rats consumed ad libi...
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Load carriage (LC) exercise may exacerbate inflammation during training. Nutritional supplementation may mitigate this response by sparing endogenous carbohydrate stores, enhancing glycogen repletion, and attenuating negative energy balance. Two studies were conducted to assess inflammatory responses to acute LC and training, with or without nutrit...
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Cold exposure in humans causes specific acute and chronic physiological responses. This paper will review both the acute and long-term physiological responses and external factors that impact these physiological responses. Acute physiological responses to cold exposure include cutaneous vasoconstriction and shivering thermogenesis which, respective...
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Background: Adaptive responses of appetite-mediating hormones to negative energy balance are thought to contribute to a counterregulatory response that drives weight regain, but they have not been studied while controlling for reduced diet volume. Objective: In this secondary analysis, we aimed to determine the effects of short-term, severe ener...
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Introduction: Little data exist regarding the long-term impact of excess weight on lower extremity musculoskeletal injury/disorder (MID) in U.S. Army Soldiers. This prospective analysis examines the association between BMI of Soldiers at accession and risk of MID. Methods: A total of 736,608 Soldiers were followed from accession into the Army, 2...
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Ca/vitamin D supplementation maintains bone health and decreases stress fracture risk during initial military training (IMT); however, there is evidence that Ca may negatively affect the absorption of other critical micronutrients, particularly Fe. The objective of this randomised, double-blind, placebo-controlled trial was to determine whether pro...
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Unlabelled: Phytonutrients have rapidly emerged as natural food chemicals possessing multifaceted biological actions that may support beneficial health outcomes. Among the vast array of phytonutrients currently being studied, sulforaphane, curcumin, quercetin, and resveratrol have been frequently reported to stimulate the expression of endogenous...
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Nindl, BC, Jaffin, DP, Dretsch, MN, Cheuvront, SN, Wesensten, NJ, Kent, ML, Grunberg, NE, Pierce, JR, Barry, ES, Scott, JM, Young, AJ, O'Connor, FG, and Deuster, PA. Human performance optimization metrics: consensus findings, gaps, and recommendations for future research. J Strength Cond Res 29(11S): S221-S245, 2015-Human performance optimization (...
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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 examine...