High Levels Of Energy Expenditure Research Articles

The Influence of Physical Activity on Stress-associated Conditions in Higher Education Students

Objectives. The purpose of the study was to substantiate the influence of physical activity on stress-associated conditions in higher education students. Materials and methods. The dataset for building the models consisted of 1115 observations, 16 independent and 3 dependent variables. As the main method we used the random forest method, the idea of which is to obtain a forecast by aggregating the predictions of a set of individual decision trees, each of which is trained on a data subset isolated from the studied sample. Results. Physical activity (PA) was found to be the most important factor in predicting stress-related conditions in university students. In addition, PA levels involving moderate and high levels of energy expenditure, as well as the number of stressful events experienced, played a significant role in predicting stress among students. In order to predict stress-related conditions in higher education students, the models “Stress”, “Increased anxiety”, and “Risk of PTSD” were built using the random forest method. The model “Stress” had the highest quality: its Accuracy was 0.77, Recall – 0.86, Precision – 0.79, and F1 Score – 0.82. The “PTSD Risk” model correctly predicted 78% of cases that indicates its good overall performance, however it correctly identified only 23% of the students who actually had the signs of this disorder. Regarding the state of anxiety, given that it is less stable than stress and PTSD, which can make model training difficult, the model built had an average accuracy of 56%, as well as reduced completeness and balance. Conclusions. Models for predicting increased anxiety and identifying students with signs of PTSD require further improvement. The implementation of developed models allows to quickly identify the manifestations of stress-related conditions in higher education students and to take the necessary measures based on the engagement in PA to prevent the development of stress-related disorders.

Alaska Backcountry Expeditionary Hunting Promotes Sustained Muscle Protein Synthesis.

We have previously described negative energy balance (ie,-9.7±3.4 MJ/d) and weight loss (Δ-1.5 ± 0.7 kg) influenced by high levels of energy expenditure (ie, 17.4±2.6 MJ/d) during remote expeditionary hunting in Alaska. Despite negative energy balance, participants retained skeletal muscle. The purpose of this pilot study was to measure skeletal muscle protein synthesis and examine molecular markers of skeletal muscle protein metabolism under similar conditions of physical and nutrient stress. The "virtual biopsy method" was used to evaluate integrated fractional synthetic rates (FSRs) of muscle protein from blood samples in 4 participants. Muscle biopsies were taken to measure molecular markers of muscle protein kinetics (ie, FSTL1, MEF2, MYOD1, B2M, and miR-1-3p, -206, -208b, 23a, and 499a) using real-time polymerase chain reaction. Our findings in 4 participants (2 females [28 and 62 y of age; 66.2 and 71.8 kg body weight; 25.5 and 26.7 kg/m2 body mass index] and 2 males [47 and 56 y of age; 87.5 and 91.4 kg body weight; 26.1 and 28.3 kg/m2 body mass index]) describe mean muscle FSRs of serum carbonic anhydrase (2.4%) and creatine kinase M-type (4.0%) and positive increments in molecular regulation. Preservation of skeletal muscle under conditions of physical and nutrient stress seems to be supported by positive inflection of skeletal muscle FSR and molecular activation.

Metabolic trade-offs associated with homeostatic adjustments in pelagic and benthic cephalopods: Comparative evaluations of NH4+/H+ transport machinery in gills

Cephalopods are ancient mollusks that can be found in many different ecological niches in the ocean ranging from the intertidal zone to the deep-sea abyss. In order to adapt to a lifestyle in various habitats, cephalopods have evolved a variety of locomotory modes to accommodate their respective habitats. Most cephalopods have relatively high metabolic rates due to their less efficient swimming mode by jet propulsion. This lifestyle is characterized by a high level of energy expenditure, fueled exclusively by protein diets that are rapidly digested and may produce metabolic nitrogenous waste NH3/NH4 +accumulation and acid-base disturbances. This study observed that the NH4 +transport rate in pelagic bigfin reef squid (Sepioteuthis lessoniana) is two times faster than benthic common octopus (Octopus vulgaris). Inhibition of Na+/H+ exchangers (NHEs) showed significant disruption of NH4 + and H+ excretory processes in gills of octopus but not in squid. However, inhibition of vacuolar-type H+-ATPase (VHA) significantly disrupts NH4 + and H+ transport rates in gills of both animals. Accordingly, for NH4 + and H+ homeostasis, benthic octopus with lower aerobic respiration rates utilize both active and Na+-driven secondary transport machinery. In order to avoid NH4 + accumulated in the blood, pelagic squids with higher aerobic respiration rates prefer active NH4 + and H+ transport mechanisms that consume ATP intensively.

Alaska Backcountry Expeditionary Hunting Promotes Exceptional Rates Of Muscle Protein Synthesis

Our Alaskan Backcountry Expeditionary Hunting (ABEH) paradigm represents an 8-14 day unscripted, remote expedition in the uninhabited Brooks Range. Despite negative energy balance (i.e., -9.7 ± 3.4 MJ/day) and significant weight loss (Δ-1.5 ± 0.7 kg) largely influenced by high levels of energy expenditure (i.e., 17.4 ± 2.6 MJ/day), participants retained skeletal muscle as determined by magnetic resonance imaging and lean tissue mass as indicated by dual energy x-ray absorptiometry. Preliminary evidence from these investigations demonstrated an increase in skeletal muscle follistatin-like protein 1, potentially enhancing the anabolism of skeletal muscle. PURPOSE: To determine integrated rates of skeletal muscle protein synthesis throughout the ABEH paradigm that may be relevant to skeletal muscle preservation. METHODS: The use of the virtual biopsy method was employed via 2H2O dosing and liquid chromatography/tandem mass spectrometry analysis to evaluate fractional synthetic rates (FSR) of muscle proteins in four participants (2 females [28 and 62 yr; 66.2 and 71.8 kg; 25.5 and 26.7 kg/m2] and 2 males [47 and 56 yr; 87.5 and 91.4 kg; 26.1 and 28.3 kg/m2]). RESULTS: As an indicator of skeletal muscle synthesis, mean FSR of serum carbonic anhydrase and creatine kinase M-type was 2.4% per day (range: 1.3-5.1% per day) and 4.0% per day (range: 1.4-8.2% per day), respectively. CONCLUSION: Our preliminary findings suggest that the ABEH-induced alterations in skeletal muscle FSR in our cohort are ~four-fold higher than reported in young individuals at baseline and ~ two-fold higher than after 3 weeks of exhaustive sprint interval training. Therefore, chronic mechanical overload may promote a sustained increase in the FSR of skeletal muscle despite limited nutritional provisions and negative energy balance. Research was supported by Pristine Ventures, Inc. Funding was also provided by an Institutional Development Award (IDeA) from the National Institute of General Medical Sciences of the National Institutes of Health under grant number 2P20GM103395 and Sloan Foundation Fellowship to Mr. Brandon Kowalski. The content is solely the responsibility of the authors and does not necessarily reflect the official views of the NIH and/or the Sloan Foundation.

Food supply and individual quality influence seabird energy expenditure and reproductive success.

Breeding animals trade off maximizing energy output to increase their number of offspring with conserving energy to ensure their own survival, leading to an energetic ceiling influenced by external, environmental factors or by internal, physiological factors. We examined whether internal or external factors limited energy expenditure by supplementally feeding breeding black-legged kittiwakes varying in individual quality, based on earlier work that defined late breeders as low-quality and early breeders as high-quality individuals. We tested whether energy expenditure increased when food availability decreased in both low- and high-quality birds; we predicted this would only occur in high-quality individuals capable of sustaining high levels of energy expenditure. Here, we find that food-supplemented birds expended less energy than control birds because they spent more time at the colony. However, foraging trips of food-supplemented birds were only slightly shorter than control birds, implying that food-supplemented birds were limited by food availability at sea similarly to control birds. Late breeders expended less energy, suggesting that low-quality individuals may not intake the energy necessary for sustaining high-energy output. Food-supplemented birds had more offspring than control birds, but offspring number did not influence energy expenditure, supporting the idea that the birds reached an energy ceiling. Males and lighter birds expended more energy, possibly compensating for relatively higher energy intake. Chick-rearing birds were working near their maximum, with highest levels of expenditure for early-laying (high-quality) individuals foraging at sea. Due to fluctuating marine environments, kittiwakes may be forced to change their foraging behaviors to maintain the balance between reproduction and survival.

AMP-activated protein kinase activation in skeletal muscle modulates exercise-induced uncoupled protein 1 expression in brown adipocyte in mouse model.

Aerobic exercise is an effective intervention in preventing obesity and is also an important factor associated with thermogenesis. There is an increasing interest in the factors and mechanisms induced by aerobic exercise that can influence the metabolism and thermogenic activity in an individual. Recent studies suggest that exercise induced circulating factors (known as ‘exerkines’), which are able to modulate activation of brown adipose tissue (BAT) and browning of white adipose tissue. However, the underlying molecular mechanisms associated with the effect of exercise‐induced peripheral factors on BAT activation remain poorly understood. Furthermore, the role of exercise training in BAT activation is still debatable. Hence, the purpose of our study is to assess whether exercise training affects the expression of uncoupled protein 1 (UCP1) in brown adipocytes via release of different blood factors. Four weeks of exercise training significantly decreased the body weight gain and fat mass gain. Furthermore, trained mice exhibit higher levels of energy expenditure and UCP1 expression than untrained mice. Surprisingly, treatment with serum from exercise‐trained mice increased the expression of UCP1 in differentiated brown adipocytes. To gain a better understanding of these mechanisms, we analysed the conditioned media obtained after treating the C2C12 myotubes with an AMP‐activated protein kinase (AMPK) activator (AICAR; 5‐aminoimidazole‐4‐carboxamide ribonucleotide), which leads to an increased expression of UCP1 when added to brown adipocytes. Our observations suggest the possibility of aerobic exercise‐induced BAT activation via activation of AMPK in skeletal muscles.Key points Exercise promotes thermogenesis by activating uncoupling protein 1 (UCP1), which leads to a decrease in the body weight gain and body fat content. However, little is known about the role of exerkines in modulating UCP1 expression and subsequent brown adipose tissue (BAT) activation.Four weeks of voluntary wheel‐running exercise reduces body weight and fat content.Exercise induces the increase in AMP‐activated protein kinase (AMPK) and slow‐type muscle fibre marker genes in skeletal muscles and promotes UCP1 expression in white and brown adipose tissues.Incubation of brown adipocytes with serum isolated from exercise‐trained mice significantly increased their UCP1 gene and protein levels; moreover, conditioned media of AMPK‐activator‐treated C2C12 myotubes induces increased UCP1 expression in brown adipocytes.These results show that aerobic exercise‐induced skeletal muscle AMPK has a significant effect on UCP1 expression in BAT.

Fam49b-deficient lymphocytes modulate whole body energy metabolism.

Abstract TCR signal strength is determined by the balance of positively regulating, and negatively regulating proteins. Fam49b is identified as new negative regulator of TCR signaling that functions by binding to active rac-1 GTPase. In the absence of Fam49b, thymocytes receive higher TCR signaling and are defective in development of conventional T cell as well as agonist selected T cells such as CD8αα+ αβ T cells. Obesity is characterized by chronic inflammation and immune dysregulation, but the link between obesity and T cells has remains unclear. We show that Fam49b-deficient mice have a high level of energy expenditure and are resistant to high fat diet induced obesity. Furthermore, the higher energy expenditure characteristic was also observed in Fam49b-deficient chimera mice. The study reveals that Fam49b deficient lymphocytes play an important role in whole body energy metabolism. [This research was supported by NIH grants R01 AI130210 and R37 AI060040]

Sex-Specific Response to Caloric Restriction After Reproductive Investment in Microcebus murinus: An Integrative Approach.

In seasonal environments, males and females usually maintain high metabolic activity during the whole summer season, exhausting their energy reserves. In the global warming context, unpredictability of food availability during summer could dramatically challenge the energy budget of individuals. Therefore, one can predict that resilience to environmental stress would be dramatically endangered during summer. Here, we hypothesized that females could have greater capacity to survive harsh conditions than males, considering the temporal shift in their respective reproductive energy investment, which can challenge them differently, as well as enhanced flexibility in females' physiological regulation. We tackled this question on the gray mouse lemur (Microcebus murinus), focusing on the late summer period, after the reproductive effort. We monitored six males and six females before and after a 2-weeks 60% caloric restriction (CR), measuring different physiological and cellular parameters in an integrative and comparative multiscale approach. Before CR, females were heavier than males and mostly characterized by high levels of energy expenditure, a more energetic mitochondrial profile and a downregulation of blood antioxidants. We observed a similar energy balance between sexes due to CR, with a decrease in metabolic activity over time only in males. Oxidative damage to DNA was also reduced by different pathways between sexes, which may reflect variability in their physiological status and life-history traits at the end of summer. Finally, females' mitochondria seemed to exhibit greater flexibility and greater metabolic potential than males in response to CR. Our results showed strong differences between males and females in response to food shortage during late summer, underlining the necessity to consider sex as a factor for population dynamics in climate change models.

The physio-metabolic effects of time-restricting liquid sugar intake to six-hour windows during the mouse active phase: The effects of active phase liquid sugar consumption

Obesity is a major public health concern and overconsumption of unhealthy fats and sugary beverages are contributing factors. Time-restricted feeding can reduce obesity-associated pathophysiological parameters by limiting the time of food consumption; however, the effects of time-restricted sugary water consumption are unknown. To examine whether liquid calorie restriction impacts metabolic health, we measured metabolic parameters in mice provided liquid sugar at various intervals during the active phase. The control (Con) group received tap water, the adlibitum fructose-glucose (ALFG) group received ad libitumsugar water and the early fructose-glucose (EFG) and late fructose-glucose (LFG) groups received liquid sugar during the first and last six hours of the active period, respectively. Each group was given free access to chow. Zeitgeber time (ZT) notation was used to set all experimental time points to lights on as ZT 0. The ALFG group exhibited elevated body and adipose tissue weights compared to the other groups and increased hepatic steatosis compared to the Con group. The ALFG group consumed more calories than the other groups during ZT 6-11, indicating that this window may be critical in the promotion of weight gain from liquid sugar consumption. The EFG group exhibited higher levels of energy expenditure than the Con and LFG groups during the first half of the active period (ZT 12-17); however, there was no difference among the groups during the second half of the active period (ZT18-23). In contrast, the EFG group exhibited lower respiratory exchange ratio than other groups during the inactive period as well as the second half of the active period, indicating that the EFG group had greater metabolic flexibility and utilized lipids when carbohydrates from liquid sugar were not available. Additionally, the EFG group was more insulin tolerant than the ALFG and Con groups. Our results support the hypothesis that time-restricted liquid calorie restriction aids in reducing the detrimental metabolic effects of sugary drink consumption.

Does the postural stability of patients with Parkinson's disease affect the physical activity?

Postural instability is one of the cardinal features in Idiopathic Parkinson's disease. It is a significant factor of disability in Parkinson's disease. We aimed to examine the physical activity levels in patients with Parkinson's disease comparing with healthy subjects and their association with the postural stability. Fifty-six Parkinson's disease patients and 58 healthy subjects were involved. The disease-specific disability of patients was determined by using Modified Hoehn and Yahr Scale and Movement Disorder Society Unified Parkinson's Disease Rating Scale. The physical activity levels of participants were evaluated using SenseWear Arm Band activity monitor. The participants used the activity monitor for seven consecutive days. The postural stability was assessed using NeuroCom Balance Master system. The Parkinson's disease group was found to take fewer steps and to have shorter duration of sleep and sedentary behavior but a higher level of energy expenditure than the healthy control group (P < 0.05). In Parkinson's disease group, the data obtained from the activity monitor were found to be in correlation with disease-specific disability and the parameters of NeuroCom Balance Master system (P < 0.05). We found that the physical activity levels of patients with a mild or moderate stage of Parkinson's disease were lower compared to healthy subjects and were affected by the disease-specific symptoms, dynamic postural instability, and walking function. To increase the activity level in Parkinson's disease, these factors should be aimed to improve, as well as designing the personalized physiotherapy programs starting from the early-mid stage.

Energy Balance and Active Lifestyle: Potential Mediators of Health and Quality of Life Perception in Aging.

The relationship between aging and perception of health and quality of life is complex and its mediation mechanisms need to be further explored. The purpose of this study was to investigate the mediating effects of total energy expenditure and intake, body mass, and body image dissatisfaction on the relationship between age and perception of health and quality of life. Forty-two senior athletes, 55 physically active, and 61 sedentary individuals (aged 55–84 years) were evaluated for total energy expenditure (EE), energy intake (EI), body mass index (BMI), absolute Body Dissatisfaction Index (BDIabx), and physical (PCS) and mental (MCS) health and quality of life perception. Multiple mediation analyses were applied to assess the relationship between age and PCS and MCS indices, through the mediators EE, EI, BMI, and BDIabx. For MCS, but not for PSC, the mediation analysis showed: (a) a direct effect of age; (b) a mediation path through EE, EI, BMI, and BDIabx; and (c) a positive total effect. The combination of positive and negative mediating effects influencing the mental health perception underlined that with advancing age, the maintenance of high levels of energy expenditure through physical activity could positively impact body image satisfaction and, in turn, mental health.

Seasonal Dynamics of Lipid Metabolism and Energy Storage in the Brazilian Free-Tailed Bat

As small, flying, mammalian endotherms, insectivorous bats are adapted to operate at high levels of energy expenditure. In response to seasonally variable challenges, we predicted that bats should balance energy budgets by flexibly adjusting aspects of their physiology or behavior in ways that elevate metabolic capacity. We examined variation in energy storage and pathways for oxidative metabolism in Brazilian free-tailed bats (Tadarida brasiliensis) related to estimated costs associated with reproduction and migration. We collected pectoral muscle and liver from female T. brasiliensis at six time points during the summer and fall and measured changes in the activity of four enzymes involved with lipid metabolism. Body mass varied substantially with life-cycle stage, suggesting that rapid accumulation and use of fat stores occurs in response to current and anticipated energy demands. Catabolic enzyme activity (carnitine palmitoyl transferase [CPT], 3-hydroxyacyl-CoA dehydrogenase [HOAD], and citrate synthase [CS]) in the muscle was increased during lactation compared with early pregnancy but exhibited no change before fall migration. While there was no temporal change in lipid biosynthetic capacity in the liver, fatty acid synthase activity was negatively correlated with body mass. Variation in body mass and enzyme activity in T. brasiliensis during the summer suggests that stored energy is mobilized and lipid oxidative capacity is increased during periods of increased demand and that lipid biosynthetic capacity is increased with depletion of fat stores. These results suggest that bats are able to flexibly adjust metabolic capacity based on energy requirement to maintain energy balance despite high levels of expenditure.

Peer-Reviewed Abstracts

Background/Purpose: The US Department of Health and Human Services recommends that children participate daily in 60 minutes of moderate to vigorous physical activity (MVPA). A threshold of >4.0 METs (metabolic equivalent of task) is considered MVPA in children. Physical education classes are ideal settings for the promotion of MVPA through the practice of continuous (walking, running) and discrete (kicking, throwing, striking) skills. Recent research in adults has determined the energy expenditure of discrete skill practice to be high while participants’ rate of perceived exertion (RPE) was low. The replication of this phenomenon in children would provide evidence for the inclusion of discrete skill practice in curricula aiming to promote MVPA. Thus, this study examined energy expenditure (METs), rate of perceived exertion (RPE), and level of fun during object projection skill performance (kicking, throwing, and striking) at three different practice intervals in children. Method: Children (N = 42, Mage = 8.1 ± 0.8 years) participated in three nine-minute experimental sessions where participants performed rounds of 5 kicks, 5 throws, and 5 strikes in blocked fashion, at three practice intervals (i.e., 30, 12, and 6 seconds). Each participant completed the three sessions in a randomized order. Participants were instructed to perform all trials with maximum effort and to report their RPE (1 “Not tired at all” – 10 “So tired, I can’t go anymore”) and level of fun (1 “Not fun at all” – 10 “The most fun I’ve ever had”) using 10-point scales. The average energy expenditure (METs) during minutes 4-8 of each nine-minute session were calculated using a COSMED K4b2 gas analyzer. Analysis/Results: Three one-way repeated measures ANOVAs for METs, RPE, and fun were conducted to examine differences across groups and sex. Data indicated a main effect for interval condition (F = 94.36, p < .001, η2 = 0.605) with decreased interval times between performance trials yielding significantly higher METs across conditions (4.5 ± 0.8, 6.3 ± 1.3, 8.3 ± 1.6 at 30-, 12-, 6-sec interval respectively). There also was a main effect for sex (F = 52.28, p < .001, η2 = 0.305), with boys demonstrating higher METs at each performance trial interval. RPE and fun analyses determined a main effect for each interval (RPE; F = 91.16, p < .001, fun; F = 96.61, p<.001) with no difference in gender at each interval. The average RPE responses were low (3.3 ± 1.8, 4.1 ± 2.2, and 4.9 ± 2.7 at 30-, 12- and 6-sec interval respectively) while average fun levels remained high (8.0 ± 1.4, 8.3 ± 1.4, and 8.7 ± 1.4 at 30-, 12-, 6-sec interval respectively). Conclusions: Results indicate that skill practice in all three interval conditions resulted in MVPA. Boys and girls reported equivalent low levels of RPE and high levels of fun. These data demonstrate that the practice of discrete skills yield high levels of energy expenditure (METs), low levels of perceived exertion, and high levels of fun. This study provides positive evidence for the inclusion of discrete skills in physical activity interventions and physical education curricula attempting to promote MVPA.

Hold your nose to prevent obesity

Obesity The sense of smell (olfaction) can affect the appreciation and anticipation of food. Riera et al. found that the activity of olfactory sensory neurons also influences energy regulation. Inhibition of olfactory perception in lean mice and mice with diet-induced obesity showed that losing the sense of smell resulted in leaner mice, but not because they ate less. Mice that could not smell had higher levels of energy expenditure and fat-burning capacity because sympathetic nerve activity became elevated in adipose tissue. Conversely, mice with hypersensitive olfaction had greater adiposity and exhibited signs of diabetes. It appears that being able to smell has a direct systemic effect on regulating body energy homeostasis. Cell Metab. 26 , 198 (2017).

Productive and environmental performance indicators analysis by a combined LCA hybrid model and real-time manufacturing process monitoring: A grinding unit process application

Among machining processes, grinding has been used to achieve high dimensional tolerances and surface quality on workpieces. Yet, high levels of energy expenditure per volume of removed material and the need for cutting fluids make grinding one of the most environmentally impactful machining processes. Furthermore, changes in parameters such as grain and bond specifications of the grinding wheel, cutting speed, and specific material removal rate can lead to different productive and environmental results. Thus, the analysis of grinding processes should not be aggregated and leveraged into a single and broad output parameter. Instead, comprehensive study should be performed, in which the most relevant process parameters, inputs and outputs are considered. This paper presents a detailed study of grinding process, including the characterization of machine subunits and production modes, along with the use of a combined life cycle assessment hybrid model and real-time monitoring system to evaluate the consumption of energy, tooling, cutting fluid and compressed air. A detailed cradle-to-gate life cycle assessment study using eleven different impact categories and a productive performance assessment were performed to evaluate the effects on varying specific material removal rate and wheel type. For equal values of specific material removal rate, the change from a conventional wheel to a cubic boron nitride represented a power requirement increase of 19–24%. Cubic boron nitride wheel achieved remarkably better results on the wheel wear and part roughness indicators for all tested conditions. The environmental performance assessment showed a strict relation between the process environmental impacts and the consumption of electric energy and cutting fluid. To conclude, despite the higher power requirements, the combination of cubic boron nitride wheel with high values of specific material removal rate optimizes both the productive and the environmental results.

Role of physical activity in regulating appetite and body fat

Recent articles in the press have questioned the role of physical activity in regulating appetite and controlling bodyweight. These articles can be confusing and misleading for the public. Yet this is a complex area and there is disagreement about the importance of physical activity even among academics. Uncertainty and misunderstanding in this area may be related to the heterogeneity of the term ‘physical activity’ which encompasses sporting pursuits with extremely high levels of energy expenditure over prolonged periods of time, as well as everyday tasks involving much lower levels of energy expenditure on an intermittent basis. This latter form of physical activity includes what has been termed ‘non-exercise activity thermogenesis’ (NEAT). In the right circumstances, physical activity can make a major contribution to the maintenance of a healthy weight even in the absence of dietary control although a combination of the two is almost certain to be more effective. In the long-term, evidence suggests that for most people exercise is likely to lead to only modest weight loss. This may be due to an insufficient amount of physical activity being performed together with compensatory changes in eating and exercise behaviours. This is hard to prove because energy intake and energy expenditure are difficult to quantify in free-living situations. Individual differences in the way people respond to exercise due to both environmental (e.g. social class, education level, income, eating and exercise behaviours of family and peers, weather etc.) and genetic factors also contribute to uncertainty about the effectiveness of physical activity for weight control. Nevertheless, physical activity remains a vital component of a healthy lifestyle due to its positive influence on energy balance as well as its potential to reduce the risk of lifestyle-related diseases.

Perceived fatigability and metabolic and energetic responses to 6-minute walk test in older women

ObjectiveTo determine the relationship between perceived fatigability and oxygen consumption, carbon dioxide production, respiratory exchange ratio and the energy cost of walking in older women. DesignObservational, cross-sectional study. ParticipantsForty-eight community-dwelling older women were recruited from senior centres in Natal, Rio Grande do Norte, Brazil. Main outcome measuresParticipants were evaluated in two different sessions. In the first session, sociodemographic and clinical factors were assessed and accelerometers were delivered. In the second session, the 6-minute walking test (6MWT) was performed and expired gases were analysed. Self-reported levels of fatigue were evaluated on a numerical scale from 1 (‘extremely energetic’) to 7 (‘extremely tired’). Severity scores for perceived and performance fatigability were calculated as the ratio of change in performance and fatigue, respectively, with walking distance. The O2 cost of walking was based on the oxygen consumption rate and the 6MWT walking speed. ResultsNo correlation was found between the severity of perceived fatigability and metabolic measures. However, the severity of perceived fatigability was significantly correlated with greater O2 cost (r=0.579, P<0.01), physical activity (r=−0.654, P<0.01), walking distance (r=−0.712, P<0.01) and severity of performance fatigability (r=0.690, P<0.01). ConclusionPerceived fatigability was not directly associated with metabolic measures; however, greater severity of perceived fatigability was associated with an increase in the O2 cost of walking. Important relationships were also found between greater severity of perceived fatigability and poor functional fitness, high level of energy expenditure and lower level of physical activity.

Adaptive changes in amino acid metabolism permit normal longevity in mice consuming a low-carbohydrate ketogenic diet

Ingestion of very low-carbohydrate ketogenic diets (KD) is associated with weight loss, lowering of glucose and insulin levels and improved systemic insulin sensitivity. However, the beneficial effects of long-term feeding have been the subject of debate. We therefore studied the effects of lifelong consumption of this diet in mice. Complete metabolic analyses were performed after 8 and 80weeks on the diet. In addition we performed a serum metabolomic analysis and examined hepatic gene expression. Lifelong consumption of KD had no effect on morbidity or mortality (KD vs. Chow, 676 vs. 630days) despite hepatic steatosis and inflammation in KD mice. The KD fed mice lost weight initially as previously reported (Kennnedy et al., 2007) and remained lighter and had less fat mass; KD consuming mice had higher levels of energy expenditure, improved glucose homeostasis and higher circulating levels of β-hydroxybutyrate and triglycerides than chow-fed controls. Hepatic expression of the critical metabolic regulators including fibroblast growth factor 21 were also higher in KD-fed mice while expression levels of lipogenic enzymes such as stearoyl-CoA desaturase-1 was reduced. Metabolomic analysis revealed compensatory changes in amino acid metabolism, primarily involving down-regulation of catabolic processes, demonstrating that mice eating KD can shift amino acid metabolism to conserve amino acid levels. Long-term KD feeding caused profound and persistent metabolic changes, the majority of which are seen as health promoting, and had no adverse effects on survival in mice.

Appetite, appetite hormone and energy intake responses to two consecutive days of aerobic exercise in healthy young men

Single bouts of exercise do not cause compensatory changes in appetite, food intake or appetite regulatory hormones on the day that exercise is performed. It remains possible that such changes occur over an extended period or in response to a higher level of energy expenditure. This study sought to test this possibility by examining appetite, food intake and appetite regulatory hormones (acylated ghrelin, total peptide-YY, leptin and insulin) over two days, with acute bouts of exercise performed on each morning. Within a controlled laboratory setting, 15 healthy males completed two, 2-day long (09:00–16:00) experimental trials (exercise and control) in a randomised order. On the exercise trial participants performed 60 min of continuous moderate-high intensity treadmill running (day one: 70.1 ± 2.5% VO2peak, day two: 70.0 ± 3.2% VO2max (mean ± SD)) at the beginning of days one and two. Across each day appetite perceptions were assessed using visual analogue scales and appetite regulatory hormones were measured from venous blood samples. Ad libitum energy and macronutrient intakes were determined from meals provided two and six hours into each day and from a snack bag provided in-between trial days. Exercise elicited a high level of energy expenditure (total = 7566 ± 635 kJ across the two days) but did not produce compensatory changes in appetite or energy intake over two days (control: 29,217 ± 4006 kJ; exercise: 28,532 ± 3899 kJ, P > 0.050). Two-way repeated measures ANOVA did not reveal any main effects for acylated ghrelin or leptin (all P > 0.050). However a significant main effect of trial (P = 0.029) for PYY indicated higher concentrations on the exercise vs. control trial. These findings suggest that across a two day period, high volume exercise does not stimulate compensatory appetite regulatory changes.

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