Exercising with low muscle glycogen content increases fat oxidation and decreases endogenous, but not exogenous carbohydrate oxidation.

BACKGROUND: Initiating aerobic exercise with low muscle glycogen content promotes greater fat and less endogenous carbohydrate oxidation during exercise. However, the extent exogenous carbohydrate oxidation increases when exercise is initiated with low muscle glycogen is unclear. PURPOSE: Determine the effects of muscle glycogen content at the onset of exercise on whole-body and muscle substrate metabolism. METHODS: Using a randomized, crossover design, 12 men (mean ±â€¯SD, age: 21 ±â€¯4 y; body mass: 83 ±â€¯11 kg; VO2peak: 44 ±â€¯3 mL/kg/min) completed 2 cycle ergometry glycogen depletion trials separated by 7-d, followed by a 24-h refeeding to elicit low (LOW; 1.5 g/kg carbohydrate, 3.0 g/kg fat) or adequate (AD; 6.0 g/kg carbohydrate, 1.0 g/kg fat) glycogen stores. Participants then performed 80 min of steady-state cycle ergometry (64 ±â€¯3% VO2peak) while consuming a carbohydrate drink (95 g glucose +51 g fructose; 1.8 g/min). Substrate oxidation (g/min) was determined by indirect calorimetry and 13C. Muscle glycogen (mmol/kg dry weight), pyruvate dehydrogenase (PDH) activity, and gene expression were assessed in muscle. RESULTS: Initiating steady-state exercise with LOW (217 ±â€¯103) or AD (396 ±â€¯70; P < 0.05) muscle glycogen did not alter exogenous carbohydrate oxidation (LOW: 0.84 ±â€¯0.14, AD: 0.87 ±â€¯0.16; P > 0.05) during exercise. Endogenous carbohydrate oxidation was lower and fat oxidation was higher in LOW (0.75 ±â€¯0.29 and 0.55 ±â€¯0.10) than AD (1.17 ±â€¯0.29 and 0.38 ±â€¯0.13; all P < 0.05). Before and after exercise PDH activity was lower (P < 0.05) and transcriptional regulation of fat metabolism (FAT, FABP, CPT1a, HADHA) was higher (P < 0.05) in LOW than AD. CONCLUSION: Initiating exercise with low muscle glycogen does not impair exogenous carbohydrate oxidative capacity, rather, to compensate for lower endogenous carbohydrate oxidation acute adaptations lead to increased whole-body and skeletal muscle fat oxidation.

Personality Traits and Occupational Demands Are Linked to Dietary Supplement Use in Soldiers: A Cross-sectional Study of Sensation Seeking Behaviors.

INTRODUCTION: Military personnel use dietary supplements (DS) more frequently and in a higher quantity than the general population. Patterns of DS used and the motivation for use among the military population are different than those of the civilian population. Soldiers are much more likely to use potentially dangerous DS purported to enhance physical performance and/or promote weight loss in spite of limited evidence regarding the safety and efficacy of these products. Sensation seeking (SS) behaviors can be associated with risky lifestyle behaviors and may be associated with use of DS by Soldiers. This study assessed Soldiers' SS behaviors in relation to DS use and various demographic factors. MATERIALS AND METHODS: Demographic and behavioral questionnaires were administered to 289 Soldiers (mean ± SD, 28 ± 6 years, 27 ± 3 kg/m2 BMI, 83% male) at three U.S. military installations. The Brief SS Scale (four 10-point subscales) and Arnett Inventory of SS (two 40-point subscales) were used to assess SS behaviors. Independent sample t-tests determined the significant differences between SS subscale scores of DS users and non-users for each type of DS (i.e., protein, multivitamin, etc.). One-way analysis of variances and Tukey's post hoc comparisons assessed differences in SS scores across demographic categories. Tukey's post hoc analyses assessed SS scores between users and non-users within the DS categories. RESULTS: Overall, 75% of Soldiers used DS ≥1 time/week. The most frequently used DS were protein/amino acids (52%), multivitamins/multiminerals (47%), "other" supplements (43%), and combination products (35%). Overall, DS users scored higher in experience seeking (8.0 ± 1.7 vs 7.5 ± 2.0; p < 0.05) and novelty (28.4 ± 3.7 vs 26.8 ± 4.7; p < 0.05) than non-users. Protein/amino acid users scored higher than non-users for all six SS traits: experience seeking (p < 0.001), boredom susceptibility (p < 0.001), thrill seeking (p < 0.001), disinhibition (p < 0.01), novelty (p < 0.001), and intensity (p < 0.001). Users of bodybuilding DS scored higher than non-users in four of the six SS traits: boredom susceptibility (p < 0.05), thrill seeking (p < 0.001), disinhibition (p < 0.01), and intensity (p < 0.001). CONCLUSIONS: Soldiers who use DS that are frequently associated with health risks scored higher for sensation-seeking characteristics which are predictors of risky behaviors. Protein/AA and combination product DS users scored higher in sensation-seeking traits and this may be due to underestimation of risk, anticipation of positive outcomes, and/or high levels of confidence in these types of DS by high sensation seekers. Additional investigation into the association of sensation-seeking behaviors as predictors of harmful DS use is warranted.

Development of a Videoconference-Adapted Version of the Community Diabetes Prevention Program, and Comparison of Weight Loss With In-Person Program Delivery.

INTRODUCTION: Effective, standardized, and easily accessible weight management programs are urgently needed for military beneficiaries. Videoconference interventions have the potential for widespread scaling, and can provide both real time interaction and flexibility in delivery times regardless of location, but there is little information on their effectiveness and acceptability. MATERIALS AND METHODS: This study as part of a larger weight loss trial describes the videoconference adaption of Group Lifestyle Balance (GLB) program, a community group-based Diabetes Prevention Program intervention, and provides a comparison of weight loss and meeting attendance between in-person and videoconference delivery modes over 12 weeks in adult family members of military service members. Forty-three participants were enrolled from two military installations and received either the videoconference-adapted or an in-person GLB program in a non-randomized trial design. Differences in program attendance and percent weight lost at 12 weeks were compared by independent samples t-tests and nonparametric methods. Group differences in the percentage of weight lost over the 12-week period were analyzed using a linear mixed model. RESULTS: All GLB intervention components were successfully delivered by videoconference with minor adaptations for the different delivery mechanism. Participant retention was 70% and 96% in the in-person and videoconference groups, respectively (p = 0.04). Completing participants in both groups lost a significant percent body weight over the 12 week intervention (p < 0.001) and there was no difference in percent body weight after 12 weeks of intervention (6.2 ± 3.2% and 5.3 ± 3.4% for in-person and videoconference at 12 weeks, respectively; p = 0.60). CONCLUSION: This study describes the first videoconference adaption of the GLB program for use in military families. Attrition was lower in the videoconference group, and there were a similar levels of weight loss in both groups regardless of delivery modality. Videoconference weight loss interventions are effective and feasible for scaling to support healthy weight management in military as well as civilian populations.

Performance Nutrition Dining Facility Intervention Improves Special Operations Soldiers' Diet Quality and Meal Satisfaction.

OBJECTIVE: To assess the impact of the Special Operations Forces Human Performance Program dining facility (DFAC) intervention on patron diet quality and meal satisfaction. DESIGN: Nonrandomized, controlled time series study using digital food photography and surveys pre-post intervention (0, 4, 8, and 12 months). SETTING: Two Fort Bragg, NC military installation DFACs. PARTICIPANTS: Volunteers (n = 688 total; n = 573 complete dataset) were US Army active duty soldiers. INTERVENTION: The DFAC intervention included food choice architecture, new performance-optimizing food recipes to increase nutrient density, revised menus to offer more performance foods daily, and nutrition labeling to influence food choice. MAIN OUTCOME MEASURES: Daily DFAC nutrient intake and Healthy Eating Index (HEI) 2010 scores. ANALYSIS: Descriptive and ANOVA statistical analyses were performed between control and intervention groups and from baseline to 4, 8, and 12 months postintervention (α = .05; 80% power). RESULTS: The intervention resulted in a higher posttest HEI score (60.1 ± 8.8 points; +3.4%; P = .005) and DFAC satisfaction compared with control (49.0 ± 10.4 points; P > .05). Improved intervention HEI scores were attributed to changes in citrus and melon fruit (+46%), red and orange vegetables (+35%), whole grains (+181%), legumes (65%), yogurt (+45%), oils (-26%), and solid fat (-18%) consumption (all P < .05). CONCLUSIONS AND IMPLICATIONS: These data illustrate that the Special Operations Forces Human Performance Program military DFAC nutrition intervention was feasible to implement and was associated with diet quality improvements. Access to high-quality ingredients and recipes may improve soldier meal quality and acceptance in other settings and warrants further investigation.

Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota.

Stress, a ubiquitous part of daily human life, has varied biological effects which are increasingly recognized as including modulation of commensal microorganisms residing in the gastrointestinal tract, the gut microbiota. In turn, the gut microbiota influences the host stress response and associated sequelae, thereby implicating the gut microbiota as an important mediator of host health. This narrative review aims to summarize evidence concerning the impact of psychological, environmental, and physical stressors on gut microbiota composition and function. The stressors reviewed include psychological stress, circadian disruption, sleep deprivation, environmental extremes (high altitude, heat, and cold), environmental pathogens, toxicants, pollutants, and noise, physical activity, and diet (nutrient composition and food restriction). Stressors were selected for their direct relevance to military personnel, a population that is commonly exposed to these stressors, often at extremes, and in combination. However, the selected stressors are also common, alone or in combination, in some civilian populations. Evidence from preclinical studies collectively indicates that the reviewed stressors alter the composition, function and metabolic activity of the gut microbiota, but that effects vary across stressors, and can include effects that may be beneficial or detrimental to host health. Translation of these findings to humans is largely lacking at present. This gap precludes concluding with certainty that transient or cumulative exposures to psychological, environmental, and physical stressors have any consistent, meaningful impact on the human gut microbiota. However, provocative preclinical evidence highlights a need for translational research aiming to elucidate the impact of stressors on the human gut microbiota, and how the gut microbiota can be manipulated, for example by using nutrition, to mitigate adverse stress responses.