Tracey J. Smith

Monitoring Energy Intake: A Hand-Held Personal Digital Assistant Provides Accuracy Comparable to Written Records

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.

Efficacy of a Meal-Replacement Program for Promoting Blood Lipid Changes and Weight and Body Fat Loss in US Army Soldiers

Excess weight is associated with negative health outcomes. Meal replacements are effective in promoting favorable body composition changes in civilian populations; however, their efficacy with military service members who have unique lifestyles is unknown. The objective of this randomized controlled trial was to determine the efficacy of the Armys education-based weight-management program, Weigh to Stay, with and without meal replacements for improving blood lipids, and to promote weight and body fat loss in overweight US Army soldiers. Soldiers (n=113; 76 males/37 females) attending Weigh to Stay at Fort Bragg, NC, in 2006/2007 were randomized to Weigh to Stay only or a commercially available meal-replacement program (two meal replacements per day) in conjunction with Weigh to Stay, and followed until Army body fat standards were met or for 6 months if standards were not met. Study completers (n=46) in both treatment groups lost weight (Weigh to Stay: -2.7+/-4.3 kg; meal replacers: -3.8+/-3.5 kg) and fat mass (Weigh to Stay, -2.7+/-3.2 kg; meal replacers: -2.9+/-2.5 kg), and improved high-density lipoprotein cholesterol concentrations (Weigh to Stay: 13+/-9 mg/dL [0.34+/-0.23 mmol/L]; meal replacers: 8+/-7 mg/dL [0.21+/-0.18 mmol/L]; P<0.05); however, no between-group differences were observed. Attrition was lower (P=0.009) and success in meeting body fat standards tended to be higher (P=0.06) for the meal replacers vs Weigh to Stay participants. Intent-to-treat analysis demonstrated that meal replacers lost more weight (1.2+/-0.5 kg), percent body fat (1.0%+/-0.4%), and fat mass (0.8+/-0.4 kg) compared to Weigh to Stay volunteers (P<0.05). Our findings suggest that meal replacement use can be recommended as a potential adjunct strategy to Weigh to Stay.

Effects of Modified Foodservice Practices in Military Dining Facilities on Ad Libitum Nutritional Intake of US Army Soldiers

BACKGROUNDnModifying foodservice practices in military dining facilities could influence ad libitum nutritional intake patterns of soldiers.nnnOBJECTIVEnWe 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).nnnDESIGNnTen 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.nnnPARTICIPANTSnVolunteers were US Army active duty soldiers recruited from among diners at 10 DFACs on Fort Bragg, NC.nnnMAIN OUTCOME MEASURESnPrimary 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.nnnRESULTSnAt 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.nnnCONCLUSIONSnThese 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.

Altered Appetite-Mediating Hormone Concentrations Precede Compensatory Overeating After Severe, Short-Term Energy Deprivation in Healthy Adults

BACKGROUNDnAdaptive 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.nnnOBJECTIVEnIn this secondary analysis, we aimed to determine the effects of short-term, severe energy deprivation (ED) on appetite and appetite-mediating hormone concentrations.nnnMETHODSnTwenty-one adults with a mean ± SD age of 21 ± 3 y and body mass index of 25 ± 3 kg/m(2) consumed isovolumetric diets provided over separate 48-h periods while increasing habitual energy expenditure by 1683 ± 329 kcal/d through light- and moderate-intensity exercise. Energy intake was matched to energy expenditure to maintain energy balance (EB) (-44 ± 92 kcal/d) or was <10% of energy expenditure to generate a -3696 ± 742-kcal/d energy deficit. Postprandial appetite, glucose, insulin, acyl ghrelin, peptide YY, pancreatic polypeptide (PP), and glucagon-like peptide-1 (GLP-1) responses and ad libitum energy intake were measured as secondary outcomes after both experimental periods.nnnRESULTSnFasting insulin (-56% ± 42%) and acyl ghrelin (-60% ± 17%) concentrations decreased during ED but not during EB (condition-by-time interaction; P-interaction ≤ 0.01), whereas fasting leptin concentrations decreased more during ED compared with during EB (-47% ± 27% compared with -20% ± 27%; P-interaction = 0.05). Postprandial insulin (57% ± 63%; P < 0.001), GLP-1 (14% ± 28%; P = 0.04), and PP (54% ± 52%; P < 0.001) areas under the curve (AUCs) were higher, whereas the acyl ghrelin AUC was lower (-56% ± 13%; P < 0.001) after ED compared with after EB. After ED, self-rated appetite was greater, and ad libitum energy intake was 811 kcal/36 h (95% CI: 184, 1439 kcal/36 h) higher relative to after EB (P = 0.01).nnnCONCLUSIONSnShort-term, severe ED suppressed acyl ghrelin concentrations and increased postprandial anorexigenic hormone concentrations. These effects preceded compensatory overeating, suggesting that in adults without obesity, altered sensitivity to appetite-mediating hormones may contribute to an adaptive counterregulatory response during the initial stages of negative EB. This trial was registered at clinicaltrials.gov as NCT01603550.

High protein diet maintains glucose production during exercise-induced energy deficit: a controlled trial

BackgroundInadequate energy intake induces changes in endogenous glucose production (GP) to preserve muscle mass. Whether addition provision of dietary protein modulates GP response to energy deficit is unclear. The objective was to determine whether exercise-induced energy deficit effects on glucose metabolism are mitigated by increased dietary protein.MethodsNineteen men ([mean ± SD] 23 ± 2 y, VO2peak 59 ± 5 ml·kg-1·min-1) were divided into three groups, two consuming moderate (MP; 0.9 g protein kg-1 d-1), and one high (HP; 1.8 g protein kg-1 d-1) protein diets (55% energy from carbohydrate) for 11 days. Following 4 days of energy balance (D1-4), energy expenditure was increased for 7 days (D5-12) in all groups. Energy intake was unchanged in two, creating a 1000 kcal d-1 deficit (DEF-MP, DEF-HP; n = 6, both groups), whereas energy balance was maintained in the third (BAL-MP, n = 7). Biochemical markers of substrate metabolism were measured during fasting rest on D4 and D12, as were GP and contribution of gluconeogenesis to endogenous glucose production (fgng) using 4-h primed, continuous infusions of [6,6-2H2]glucose (dilution-method) and [2-13C]glycerol (MIDA technique). Glycogen breakdown (GB) was derived from GP and fgng.ResultsPlasma β-hydroxybutyrate levels increased, and plasma glucose and insulin declined from D4 to D12, regardless of group. DEF-MP experienced decreased plasma GP from D4 to D12 ([mean change ± SD] 0.24 ± 0.24 mg·kg-1·min-1), due to reduced GB from D4 (1.40 ± 0.28 mg·kg-1·min-1) to D12 (1.16 ± 0.17 mg·kg-1·min-1), P < 0.05. Conversely, BAL-MP and DEF-HP sustained GP from D4 to D12 ([mean change ± SD] 0.1 ± 0.5 and 0.0 ± 0.2 mg·kg-1·min-1, respectively) by maintaining GB.ConclusionExercise-induced energy deficit decreased GP and additional dietary protein mitigated that effect.

A suction blister model reliably assesses skin barrier restoration and immune response.

Skin wound healing models can be used to detect changes in immune function in response to interventions. This study used a test-retest format to assess the reliability of a skin suction blister procedure for quantitatively evaluating human immune function in repeated measures type studies. Up to eight suction blisters (~30 mm(2)) were induced via suction on each participants left and right forearm (randomized order; blister session 1 and 2), separated by approximately one week. Fluid was sampled from each blister, and the top layer of each blister was removed to reveal up to eight skin wounds. Fluid from each wound was collected 4, 7 and 24h after blisters were induced, and proinflammatory cytokines were measured. Transepidermal water loss (TEWL), to assess skin barrier recovery, was measured daily at each wound site until values were within 90% of baseline values (i.e., unbroken skin). Sleep, stress and inflammation (i.e., factors that affect wound healing and immune function), preceding the blister induction, were assessed via activity monitors (Actical, Philips Respironics, Murrysville, Pennsylvania), the Perceived Stress Scale (PSS) and C-reactive protein (CRP), respectively. Area-under-the-curve and TEWL, between blister session 1 and 2, were compared using Pearson correlations and partial correlations (controlling for average nightly sleep, PSS scores and CRP). The suction blister method was considered reliable for assessing immune response and skin barrier recovery if correlation coefficients reached 0.7. Volunteers (n=16; 12 M; 4F) were 23 ± 5 years [mean ± SD]. Time to skin barrier restoration was 4.9 ± 0.8 and 4.8 ± 0.9 days for sessions 1 and 2, respectively. Correlation coefficients for skin barrier restoration, IL-6, IL-8 and MIP-1α were 0.9 (P<0.0001), 0.7 (P=0.008) and 0.9 (P<0.0001), respectively. When average nightly sleep, PSS scores and CRP (i.e., percent difference between sessions 1 and 2) were taken into consideration, correlations in immune response between sessions 1 and 2 were improved for IL-8 (0.8, P=0.002) and TNF-α (0.7, P=0.02). The skin suction blister method is sufficiently reliable for assessing skin barrier restoration and immune responsiveness. This data can be used to determine sample sizes for cross-sectional or repeated-measures types of studies testing the impact of various stressors on immune response, and/or the efficacy of interventions to mitigate decrements in immune response to stress.

Impact of sleep restriction on local immune response and skin barrier restoration with and without “multinutrient” nutrition intervention

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 experimental wound, and determined the influence of habitual protein intake (1.5 g·kg-1·day-1) supplemented with arginine, glutamine, zinc sulfate, vitamin C, vitamin D3, and omega-3 fatty acids compared with lower protein intake (0.8 g·kg-1·day-1) without supplemental nutrients on these outcomes. Wounds were created in healthy adults by removing the top layer of less than or equal to eight forearm blisters induced via suction, after adequate sleep (AS) or 48 h of a 72-h sleep restriction period (SR; 2-h nightly sleep). A subset of participants undergoing sleep restriction received supplemental nutrients during and after sleep restriction (SR+). Wound fluid was serially sampled 48 h postblistering to assess local cytokine responses. The IL-8 response of wound fluid was higher for AS compared with SR [area-under-the-curve (log10), 5.1u2009±u20090.2 and 4.9u2009±u20090.2 pg/ml, respectively; P = 0.03]; and both IL-6 and IL-8 concentrations were higher for SR+ compared with SR ( P < 0.0001), suggestive of a potentially enhanced early wound healing response. Skin barrier recovery was shorter for AS (4.2u2009±u20090.9 days) compared with SR (5.0u2009±u20090.9 days) ( P = 0.02) but did not differ between SR and SR+ ( P = 0.18). Relatively modest sleep disruption delays wound healing. Supplemental nutrition may mitigate some decrements in local immune responses, without detectable effects on wound healing rate. NEW & NOTEWORTHY The data herein characterizes immune function in response to sleep restriction in healthy volunteers with and without nutrition supplementation. We used a unique skin wound model to show that sleep restriction delays skin barrier recovery, and nutrition supplementation attenuates decrements in local immune responses produced by sleep restriction. These findings support the beneficial effects of adequate sleep on immune function. Additional studies are necessary to characterize practical implications for populations where sleep restriction is unavoidable.

Sleep restriction and cognitive load affect performance on a simulated marksmanship task

Sleep restriction degrades cognitive and motor performance, which can adversely impact job performance and increase the risk of accidents. Military personnel are prone to operating under sleep restriction, and previous work suggests that military marksmanship may be negatively affected under such conditions. Results of these studies, however, are mixed and have often incorporated additional stressors (e.g. energy restriction) beyond sleep restriction. Moreover, few studies have investigated how the degree of difficulty of a marksmanship task impacts performance following sleep restriction. The purpose of the current experiment was to study the effects of sleep restriction on marksmanship while minimizing the potential influence of other forms of stress. A friend–foe discrimination challenge with greater or lesser degrees of complexity (high versus low load) was used as the primary marksmanship task. Active duty Soldiers were recruited, and allowed 2 h of sleep every 24 h over a 72‐h testing period. Marksmanship tasks, cognitive assessment metrics and the NASA‐Task Load Index were administered daily. Results indicated that reaction times to shoot foe targets and signal friendly targets slowed over time. In addition, the ability to correctly discriminate between friend and foe targets significantly decreased in the high‐cognitive‐load condition over time despite shot accuracy remaining stable. The NASA‐Task Load Index revealed that, although marksmanship performance degraded, participants believed their performance did not change over time. These results further characterize the consequences of sleep restriction on marksmanship performance and the perception of performance, and reinforce the importance of adequate sleep among service members when feasible.