Laboratory and field methods for measuring human energy expenditure

Stone toolmaking energy expenditure differs between novice and expert toolmakers

OBJECTIVES

This study investigates the energetic costs associated with Oldowan-style flake production and how skill differences influence these costs.

MATERIALS AND METHODS

Nine adult participants, including novice and expert toolmakers, underwent a 2-h experimental session where we measured energy expenditure and flaking outcomes. We measured body mass (kg), percent body fat, and fat-free mass (kg) and used open-circuit indirect calorimetry to quantify energy expenditure. The lithic analysis used standard linear and mass measurements on the resulting cores and flakes. Qualitative observations from the video recordings provide insight into the subject's body positions and hand grips.

RESULTS

Results reveal significant differences in energy expenditure between novice and expert toolmakers, with experts demonstrating lower overall energy expenditure. Additionally, experts produced more flakes, reduced greater core mass per unit of energy expenditure, and exhibited distinct body positions, hand grips, and core/flake morphologies compared with novices.

DISCUSSION

The study provides novel insights into the bio-cultural impacts of stone toolmaking skill acquisition, suggesting that skilled performance reduces the metabolic costs of stone tool production. These findings contribute to debates surrounding the origins of human cultural capacities and highlight the importance of including energy expenditure measures in knapping experiments. Moreover, the results suggest that the presence or absence of expertise in the Paleolithic would have fundamentally altered selective pressures and the reliability of skill reproduction. This study enhances our understanding of differences in stone toolmaking skill and their implications for human energy allocation strategies during early technological evolution.

Validation of predictive equations to estimate resting metabolic rate of females and males across different activity levels

OBJECTIVES

Using equations to predict resting metabolic rate (RMR) has yielded different degrees of validity, particularly when sex and different physical activity levels were considered. Therefore, the purpose of the present study was to determine the validity of several different predictive equations to estimate RMR in female and male adults with varying physical activity levels.

METHOD

We measured the RMR of 50 adults (26 females and 24 males) evenly distributed through activity levels varying from sedentary to ultra-endurance. Body composition was measured by dual X-ray absorptiometry and physical activity was monitored by accelerometry. Ten equations to predict RMR were applied (using Body Mass [BM]: Harris & Benedict, 1919; Mifflin et al., 1990 [MifflinBM]; Pontzer et al., 2021 [PontzerBM]; Schofield, 1985; FAO/WHO/UNU, 2004; and using Fat-Free Mass (FFM): Cunningham, 1991; Johnstone et al., 2006; Mifflin et al., 1990 [MifflinFFM]; Nelson et al. 1992; Pontzer et al., 2021 [PontzerFFM]). The accuracy of these equations was analyzed, and the effect of sex and physical activity was evaluated using different accuracy metrics.

RESULTS

Equations using BM were less accurate for females, and their accuracy was influenced by physical activity and body composition. FFM equations were slightly less accurate for males but there was no obvious effect of physical activity or other sample parameters. PontzerFFM provides higher accuracy than other models independent of the magnitude of RMR, sex, activity levels, and sample characteristics.

CONCLUSION

Equations using FFM were more accurate than BM equations in our sample. Future studies are needed to test the accuracy of RMR prediction equations in diverse samples.

Three common assumptions about inflammation, aging, and health that are probably wrong

Chronic inflammation contributes to the onset and progression of cardiovascular disease and other degenerative diseases of aging. But does it have to? This article considers the associations among inflammation, aging, and health through the lens of human population biology and suggests that chronic inflammation is not a normal nor inevitable component of aging. It is commonly assumed that conclusions drawn from research in affluent, industrialized countries can be applied globally; that aging processes leading to morbidity and mortality begin in middle age; and that inflammation is pathological. These foundational assumptions have shifted focus away from inflammation as a beneficial response to infection or injury and toward an understanding of inflammation as chronic, dysregulated, and dangerous. Findings from community-based studies around the world-many conducted in areas with relatively high burdens of infectious disease-challenge these assumptions by documenting substantial variation in levels of inflammation and patterns of association with disease. They also indicate that nutritional, microbial, and psychosocial environments in infancy and childhood play important roles in shaping inflammatory phenotypes and their contributions to diseases of aging. A comparative, developmental, and ecological approach has the potential to generate novel insights into the regulation of inflammation and how it relates to human health over the life course.

Longitudinal estimates of resting energy expenditure using predictive equations in individuals with excess weight after weight loss: A systematic review with meta-analysis

BACKGROUND & AIMS

To determine which resting energy expenditure (REE) predictive equation has the lowest bias in the aggregate level in individuals with excess weight during weight loss interventions.

METHODS

Searches were performed in MEDLINE, Web of Science, Scopus, CENTRAL and gray literature databases. Longitudinal studies on weight loss interventions which evaluated REE by predictive equations compared to that measured by indirect calorimetry in adults with excess weight at different follow-up times were included. Meta-analyses were performed with the differences between biases of predictive equations of the REE at the different follow-up times of weight loss.

RESULTS

Of the total of 2178 occurrences found in the databases, only eight studies were included. The Harris-Benedict (1919) equation showed the smallest differences between bias up to the third month (MD = 103.33 kcal; 95%CI = -39.01; 245.67), in the sixth month (MD = 59.16 kcal; 95%CI = 8.74; 109.57) and at the 12th month (MD = -71.41 kcal; 95%CI = -150.38; 7.55) of weight loss follow-up. Weight loss does not seem to have an effect on bias at different follow-up times.

CONCLUSION

Harris-Benedict (1919) equation seems to be the most adequate to assess the REE of individuals with excess weight during weight loss. However, the finding of large estimated predictive intervals may indicate that predictive equations may not be handy tools for individuals losing and regaining weight due to changes other than body weight.

Energetic costs of testosterone in two subsistence populations

OBJECTIVE

Testosterone plays a role in mediating energetic trade-offs between growth, maintenance, and reproduction. Investments in a high testosterone phenotype trade-off against other functions, particularly survival-enhancing immune function and cellular repair; thus only individuals in good condition can maintain both a high testosterone phenotype and somatic maintenance. While these effects are observed in experimental manipulations, they are difficult to demonstrate in free-living animals, particularly in humans. We hypothesize that individuals with higher testosterone will have higher energetic expenditures than those with lower testosterone.

METHODS

Total energetic expenditure (TEE) was quantified using doubly labeled water in n = 40 Tsimane forager-horticulturalists (50% male, 18-87 years) and n = 11 Hadza hunter-gatherers (100% male, 18-65 years), two populations living subsistence lifestyles, high levels of physical activity, and high infectious burden. Urinary testosterone, TEE, body composition, and physical activity were measured to assess potential physical and behavioral costs associated with a high testosterone phenotype.

RESULTS

Endogenous male testosterone was significantly associated with energetic expenditure, controlling for fat free mass; a one standard deviation increase in testosterone is associated with the expenditure of an additional 96-240 calories per day.

DISCUSSION

These results suggest that a high testosterone phenotype, while beneficial for male reproduction, is also energetically expensive and likely only possible to maintain in healthy males in robust condition.

Human energetic stress associated with upregulation of spatial cognition

OBJECTIVES

Evolutionary life history theory has a unique potential to shed light on human adaptive capabilities. Ultra-endurance challenges are a valuable experimental model allowing the direct testing of phenotypic plasticity via physiological trade-offs in resource allocation. This enhances our understanding of how the body prioritizes different functions when energetically stressed. However, despite the central role played by the brain in both hominin evolution and metabolic budgeting, cognitive plasticity during energetic deficit remains unstudied.

MATERIALS

We considered human cognitive plasticity under conditions of energetic deficit by evaluating variability in performance in three key cognitive domains. To achieve this, cognitive performance in a sample of 48 athletes (m = 29, f = 19) was assessed before and after competing in multiday ultramarathons.

RESULTS

We demonstrate that under conditions of energetic deficit, performance in tasks of spatial working memory (which assessed ability to store location information, promoting landscape navigation and facilitating resource location and calorie acquisition) increased. In contrast, psychomotor speed (reaction time) remained unchanged and episodic memory performance (ability to recall information about specific events) decreased.

DISCUSSION

We propose that prioritization of spatial working memory performance during conditions of negative energy balance represents an adaptive response due to its role in facilitating calorie acquisition. We discuss these results with reference to a human evolutionary trajectory centred around encephalisation. Encephalisation affords great plasticity, facilitating rapid responses tailored to specific environmental conditions, and allowing humans to increase their capabilities as a phenotypically plastic species.

Patterns of energy allocation during energetic scarcity; evolutionary insights from ultra-endurance events

Exercise physiologists and evolutionary biologists share a research interest in determining patterns of energy allocation during times of acute or chronic energetic scarcity.. Within sport and exercise science, this information has important implications for athlete health and performance. For evolutionary biologists, this would shed new light on our adaptive capabilities as a phenotypically plastic species. In recent years, evolutionary biologists have begun recruiting athletes as study participants and using contemporary sports as a model for studying evolution. This approach, known as human athletic palaeobiology, has identified ultra-endurance events as a valuable experimental model to investigate patterns of energy allocation during conditions of elevated energy demand, which are generally accompanied by an energy deficit. This energetic stress provokes detectable functional trade-offs in energy allocation between physiological processes. Early results from this modelsuggest thatlimited resources are preferentially allocated to processes which could be considered to confer the greatest immediate survival advantage (including immune and cognitive function). This aligns with evolutionary perspectives regarding energetic trade-offs during periods of acute and chronic energetic scarcity. Here, we discuss energy allocation patterns during periods of energetic stress as an area of shared interest between exercise physiology and evolutionary biology. We propose that, by addressing the ultimate "why" questions, namely why certain traits were selected for during the human evolutionary journey, an evolutionary perspective can complement the exercise physiology literature and provide a deeper insight of the reasons underpinning the body's physiological response to conditions of energetic stress.

EVOBREATH. Datasets for evolutionary bioenergetics research on anthropology

Human bioenergetics has been incorporated into the palaeobiology of human ancestors during the last years to broaden our understanding of Human Evolution. The hypotheses based solely on the taxonomy and phylogenetic relationships of the fossil record, cannot easily explain many of the questions about the physiology of past humans. Data on the energetics and physiology of recent humans, together with comprehensive analyses of body proportions and body composition in relation to human metabolism, are needed to understand the evolutionary constraints of hominin ecophysiology. Furthermore, specific datasets including energetic data from modern humans are required to model hominin palaeophysiology. EVOBREATH Datasets were gradually developed since 2013 to store and manage all the data obtained in the Research Programs on Experimental Energetics developed by the Palaeophisiology and Human Ecology Group and the Palaeoecology of Mammals Group of the National Research centre on Human Evolution (CENIEH, Burgos, Spain). All experimental tests were developed either in the CENIEH BioEnergy and Motion Lab (LabBioEM) or in the field, using mobile devices. Datasets include quantitative experimental data related to human anthropometry (Height, Weight, all postcranial dimensions and segments, including hands and feet, and computation of anatomical indices), body composition (fat mass, fat-free mass, muscular mass, body water), and energetics (resting metabolic rate and energetic expenditure in different physical activities, oxygen consumption (O₂) and carbon dioxide (CO₂) production measured breath-by-breath) obtained in multiple studies with in vivo subjects of different ages (adults, adolescents and children) and both sexes (n = 501). These datasets are useful to optimize the time-consuming process of generating experimental data and to facilitate their reuse by the scientific community. Researchers can readily employ the datasets in their own research endeavours.

Validation of the 24-hour perceived exertion recall survey (PERS) in women in rural Tigray, Ethiopia

Background

Physical activity affects nutritional status and health. Currently, there are few validated survey tools for estimating physical activity in rural areas of low-income countries, including Ethiopia, which limits the ability of researchers to assess how physical activity affects nutritional status.

Objectives

This study used accelerometry to validate 2 in-person questionnaires, the global physical activity questionnaire (GPAQ) and the 24-h perceived exertion recall survey (PERS).

Methods

This study recruited 180 women aged between 18 and 45 y living in rural Tigray, Ethiopia. Participants had previously participated in an impact evaluation of a public work safety net. They wore an accelerometer for 8 d and responded to perceived exertion questionnaires twice. Data were collected on 89 women during the short rainy period and 91 women during the main rainy season. A survey method was considered valid if the proportion of time spent in moderate or vigorous physical activity (MVPA) levels had a Pearson's correlation coefficient of >0.40 to the proportion of time spent in MVPA recorded by accelerometry.

Results

The GPAQ had high reliability, but the overall validity was poorer than accelerometry. The proportion of time spent in MVPA according to the accelerometer was associated with discordance between GPAQ and accelerometry. MVPA levels, as measured by the 24-h PERS, had a fair agreement with accelerometry. The agreement increased to moderate/acceptable when adjusted for season and BMI.

Conclusions

The 24-h PERS is a valid tool for estimating the physical activity of women living in rural highland Ethiopia. It can be used in future research to understand the physical activity demands of living in rural highland Ethiopia, enabling more targeted programs to address undernutrition.

Measuring food insecurity: An introduction to tools for human biologists and ecologists

OBJECTIVE

Food insecurity is a significant and growing concern undermining the wellbeing of 30% of the global population. Food in/security is a complex construct consisting of four dimensions: availability, access, utilization, and stability, making it challenging to measure. We provide a toolkit human biologists/ecologists can use to advance research on this topic.

METHODS

We review the strengths and limitations of common tools used to measure food access and utilization, the two dimensions most proximate to people's lived experience, and emphasize tools that provide data needed to best link food security with human biological outcomes. We also discuss methods that provide contextual data human biologists/ecologists will find useful for study design, ensuring instrument validity, and improving data quality.

RESULTS

Food access is principally measured using experience-based instruments that emphasize economic access. Social access, such as food sharing, is under-studied and we recommend using social network analysis to explore this dimension. In terms of utilization, emphasis has been on food choice measured as dietary diversity. Food preparation and intrahousehold distribution, also part of the utilization dimension, are less studied and standardized instruments for measuring both are lacking. The embodiment of food insecurity has focused on child growth, although a growing literature addresses adult mental wellbeing and chronic and infectious disease risk.

CONCLUSIONS

We see the potential to expand outcomes to include reproductive and immune function, physical activity, and the gut microbiome. Human biologists/ecologists are well-positioned to advance understanding of the human health impacts of food insecurity and provide data to support intervention efforts.

Comparison of Actual and Predicted Resting Metabolic Rate in Women with Lipedema

Background: An adequate dietary energy supply is particularly important in patients with lipedema as it promotes weight and fat loss. Accurate estimation of resting metabolic rate (RMR) allows implementing a proper calorie restriction diet in patients with lipedema. Our study aimed to compare actual resting metabolic rate (aRMR) with predicted resting metabolic rate (pRMR) in women with lipedema and to determine the association between individual body composition parameters, body mass index, and aRMR. Methods and Results: A total of 108 women diagnosed with lipedema were enrolled in the study. aRMR was obtained by indirect calorimetry (IC) using FitMate WM metabolic system (Cosmed, Rome, Italy). pRMR was estimated with predictive equations and bioelectric impedance analysis (BIA). All body composition parameters were based on BIA. The mean aRMR in the study group was 1705.2 ± 320.7 kcal/day. This study found the agreement of predictive equations compared to IC is low (<60%). Most methods of predicted RMR measurement used in our study significantly underpredicted aRMR in patients with lipedema. Therefore, the most applied equations remain useless in clinical practice in this specific population due to large individual differences among the studied women. Conclusions: IC is the best tool to evaluate RMR in evaluated patients with lipedema. It is necessary to propose a new equation to RMR determination in clinical practice.

Multiple propane gas burn rates procedure to determine accuracy and linearity of indirect calorimetry systems: an experimental assessment of a method

Objective

Indirect calorimetry (IC) systems measure the fractions of expired carbon dioxide (F_eCO₂), and oxygen (F_eO₂) recorded at the mouth to estimate whole-body energy production. The fundamental principle of IC relates to the catabolism of high-energy substrates such as carbohydrates and lipids to meet the body's energy needs through the oxidative process, which are reflected in the measured oxygen uptake rates (V̇O₂) and carbon dioxide production rates (V̇CO₂). Accordingly, it is important to know the accuracy and validity of V̇O₂and V̇CO₂ measurements when estimating energy production and substrate partitioning for research and clinical purposes. Although several techniques are readily available to assess the accuracy of IC systems at a single point for V̇CO₂ and V̇O₂, the validity of such procedures is limited when used in testing protocols that incorporate a wide range of energy production (e.g., basal metabolic rate and maximal exercise testing). Accordingly, we built an apparatus that allowed us to manipulate propane burn rates in such a way as to assess the linearity of IC systems. This technical report aimed to assess the accuracy and linearity of three IC systems using our in-house built validation procedure.

Approach

A series of trials at different propane burn rates (PBR) (i.e., 200, 300, 400, 500, and 600 mL min^-1) were run on three IC systems: Sable, Moxus, and Oxycon Pro. The experimental values for V̇O₂ and V̇CO₂ measured on the three IC systems were compared to theoretical stoichiometry values.

Results

A linear relationship was observed between increasing PBR and measured values for V̇O₂and V̇CO₂ (99.6%, 99.2%, 94.8% for the Sable, Moxus, and Jaeger IC systems, respectively). In terms of system error, the Jaeger system had significantly (p < 0.001) greater V̇O₂(mean difference (M) = -0.057, standard error (SE) = 0.004), and V̇CO₂(M = -0.048, SE = 0.002) error compared to either the Sable (V̇O₂, M = 0.044, SE = 0.004; V̇CO₂, M = 0.024, SE = 0.002) or the Moxus (V̇O2, M = 0.046, SE = 0.004; V̇CO₂, M = 0.025, SE = 0.002) IC systems. There were no significant differences between the Sable or Moxus IC systems.

Conclusion

The multiple PBR approach permitted the assessment of linearity of IC systems in addition to determining the accuracy of fractions of expired gases.

Enhancing instantaneous oxygen uptake estimation by non-linear model using cardio-pulmonary physiological and motion signals

Oxygen uptake (VO₂) is an important parameter in sports medicine, health assessment and clinical treatment. At present, more and more wearable devices are used in daily life, clinical treatment and health care. The parameters obtained by wearables have great research potential and application prospect. In this paper, an instantaneous VO₂ estimation model based on XGBoost was proposed and verified by using data obtained from a medical-grade wearable device (Beijing SensEcho) at different posture and activity levels. Furthermore, physiological characteristics extracted from single-lead electrocardiogram, thoracic and abdominal respiration signal and tri-axial acceleration signal were studied to optimize the model. There were 29 healthy volunteers recruited for the study to collect data while stationary (lying, sitting, standing), walking, Bruce treadmill test and recuperating with SensEcho and the gas analyzer (Metalyzer 3B). The results show that the VO₂ values estimated by the proposed model are in good agreement with the true values measured by the gas analyzer (R² = 0.94 ± 0.03, n = 72,235), and the mean absolute error (MAE) is 1.83 ± 0.59 ml/kg/min. Compared with the estimation method using a separate heart rate as input, our method reduced MAE by 54.70%. At the same time, other factors affecting the performance of the model were studied, including the influence of different input signals, gender and movement intensity, which provided more enlightenment for the estimation of VO₂. The results show that the proposed model based on cardio-pulmonary physiological signals as inputs can effectively improve the accuracy of instantaneous VO₂ estimation in various scenarios of activities and was robust between different motion modes and state. The VO₂ estimation method proposed in this paper has the potential to be used in daily life covering the scenario of stationary, walking and maximal exercise.

Brown adipose tissue thermogenesis among young adults in northeastern Siberia and Midwest United States and its relationship with other biological adaptations to cold climates

OBJECTIVES

Recent research suggests that brown adipose tissue (BAT) plays a functional role in non-shivering thermogenesis; however, few studies have examined population variation in BAT or its relationship with other mechanisms of adaptation to cold stress. This study characterized BAT thermogenesis and other adaptive responses to low temperatures among Indigenous Siberian young adults and young adults living near Chicago, IL.

MATERIALS AND METHODS

We recruited 72 Yakut participants (42 females; 30 males) and 54 participants in Evanston, IL (40 females; 14 males). Anthropometric dimensions and resting metabolic rate (RMR) were measured, and we calculated percent divergence in RMR from expected values (divRMR). We also quantified change in supraclavicular temperature, sternum temperature, and energy expenditure after a mild cooling condition.

RESULTS

Participants in Yakutia were less likely to shiver during the cooling condition (p < .05) and exhibited significantly greater evidence of BAT thermogenesis, warmer sternum temperatures, and higher divRMR than participants in Evanston (p < .05). Additionally, the relationship between change in supraclavicular temperature and energy expenditure differed between the two samples.

CONCLUSIONS

Yakut young adults displayed greater evidence of BAT thermogenesis in response to mild cooling compared with young adults living near Chicago, IL. Furthermore, the relationship between BAT thermogenesis and change in energy expenditure appears to be stronger among Yakut adults. Adults that exhibited greater metabolic response to cold stress, such as higher BAT thermogenesis and divRMR, maintained warmer sternum temperatures. These results highlight the degree to which adaptation to cold climates involves multiple integrated biological pathways.

Adaptations, Safety Factors, Limitations and Trade-Offs in Human Exercise Performance

Objectives

This review will describe how human exercise performance at the highest level is exquisitely orchestrated by a set of responses by all body systems related to the evolutionary adaptations that have taken place over a long history. The review will also describe how many adaptations or features are co-opted (exaptations) for use in different ways and have utility other than for selective advantage.

Methods

A review of the literature by relevant search engines and reference lists in key published articles using the terms, performance, limitations, regulation, trade-offs as related to exercise, indicates that there are at least three areas which could be considered key in understanding the evolutionary basis of human exercise performance.

Results

First, there is a basic assumption that exaptations have limitations or capacities which cannot be exceeded which in turn will limit our physical performance. Second, it is thought that some biological systems and tissues have additional capacity which is rarely fully accessed by the organism; referred to as a safety factor. Third, there are biological trade-offs which occur when there is an increase in one trait or characteristic traded for a decrease in another.

Conclusions

Adaptations have resulted in safety factors for body systems and tissues with trade-offs that are most advantageous for human performance for a specific environment.

Alternative Metabolic Strategies are Employed by Endurance Runners of Different Body Sizes; Implications for Human Evolution

Objective

A suite of adaptations facilitating endurance running (ER) evolved within the hominin lineage. This may have improved our ability to reach scavenging sites before competitors, or to hunt prey over long distances. Running economy (RE) is a key determinant of endurance running performance, and depends largely on the magnitude of force required to support body mass. However, numerous environmental factors influence body mass, thereby significantly affecting RE. This study tested the hypothesis that alternative metabolic strategies may have emerged to enable ER in individuals with larger body mass and poor RE.

Methods

A cohort of male (n = 25) and female (n = 19) ultra-endurance runners completed submaximal and exhaustive treadmill protocols to determine RE, and V̇O2Max.

Results

Body mass was positively associated with sub-maximal oxygen consumption at both LT1 (male r=0.66, p<0.001; female LT1 r=0.23, p=0.177) and LT2 (male r=0.59, p=0.001; female r=0.23, p=0.183) and also with V̇O2Max (male r=0.60, p=0.001; female r=0.41, p=0.046). Additionally, sub-maximal oxygen consumption varied positively with V̇O2Max in both male (LT1 r=0.54, p=0.003; LT2 r=0.77, p<0.001) and female athletes (LT1 r=0.88, p<0.001; LT2 r=0.92, p<0.001).

Conclusions

The results suggest that, while individuals with low mass and good RE can glide economically as they run, larger individuals can compensate for the negative effects their mass has on RE by increasing their capacity to consume oxygen. The elevated energy expenditure of this low-economy high-energy turnover approach to ER may bring costs associated with energy diversion away from other physiological processes, however.

A recurrent neural network architecture to model physical activity energy expenditure in older people

Through the quantification of physical activity energy expenditure (PAEE), health care monitoring has the potential to stimulate vital and healthy ageing, inducing behavioural changes in older people and linking these to personal health gains. To be able to measure PAEE in a health care perspective, methods from wearable accelerometers have been developed, however, mainly targeted towards younger people. Since elderly subjects differ in energy requirements and range of physical activities, the current models may not be suitable for estimating PAEE among the elderly. Furthermore, currently available methods seem to be either simple but non-generalizable or require elaborate (manual) feature construction steps. Because past activities influence present PAEE, we propose a modeling approach known for its ability to model sequential data, the recurrent neural network (RNN). To train the RNN for an elderly population, we used the growing old together validation (GOTOV) dataset with 34 healthy participants of 60 years and older (mean 65 years old), performing 16 different activities. We used accelerometers placed on wrist and ankle, and measurements of energy counts by means of indirect calorimetry. After optimization, we propose an architecture consisting of an RNN with 3 GRU layers and a feedforward network combining both accelerometer and participant-level data. Our efforts included switching mean to standard deviation for down-sampling the input data and combining temporal and static data (person-specific details such as age, weight, BMI). The resulting architecture produces accurate PAEE estimations while decreasing training input and time by a factor of 10. Subsequently, compared to the state-of-the-art, it is capable to integrate longer activity data which lead to more accurate estimations of low intensity activities EE. It can thus be employed to investigate associations of PAEE with vitality parameters of older people related to metabolic and cognitive health and mental well-being.

Recommendations for Determining the Validity of Consumer Wearables and Smartphones for the Estimation of Energy Expenditure: Expert Statement and Checklist of the INTERLIVE Network

BACKGROUND

Consumer wearables and smartphone devices commonly offer an estimate of energy expenditure (EE) to assist in the objective monitoring of physical activity to the general population. Alongside consumers, healthcare professionals and researchers are seeking to utilise these devices for the monitoring of training and improving human health. However, the methods of validation and reporting of EE estimation in these devices lacks rigour, negatively impacting on the ability to make comparisons between devices and provide transparent accuracy.

OBJECTIVES

The Towards Intelligent Health and Well-Being Network of Physical Activity Assessment (INTERLIVE) is a joint European initiative of six universities and one industrial partner. The network was founded in 2019 and strives towards developing best-practice recommendations for evaluating the validity of consumer wearables and smartphones. This expert statement presents a best-practice validation protocol for consumer wearables and smartphones in the estimation of EE.

METHODS

The recommendations were developed through (1) a systematic literature review; (2) an unstructured review of the wider literature discussing the potential factors that may introduce bias during validation studies; and (3) evidence-informed expert opinions from members of the INTERLIVE network.

RESULTS

The systematic literature review process identified 1645 potential articles, of which 62 were deemed eligible for the final dataset. Based on these studies and the wider literature search, a validation framework is proposed encompassing six key domains for validation: the target population, criterion measure, index measure, testing conditions, data processing and the statistical analysis.

CONCLUSIONS

The INTERLIVE network recommends that the proposed protocol, and checklists provided, are used to standardise the testing and reporting of the validation of any consumer wearable or smartphone device to estimate EE. This in turn will maximise the potential utility of these technologies for clinicians, researchers, consumers, and manufacturers/developers, while ensuring transparency, comparability, and replicability in validation.

TRIAL REGISTRATION

PROSPERO ID: CRD42021223508.

Is constitutional thinness really different from anorexia nervosa? A systematic review and meta-analysis

A growing interest in constitutional thinness has been observed in the last decades, but the publications however cover various fields of study and report equivocal results. The present work systematically reviewed any clinical trials enrolling participants with constitutional thinness and bibliographic researches were performed between December 2018 and June 2020. From a total of 1 212 records initially identified, 402 records were removed as duplicates, 381 articles were excluded based on titles or abstracts and 390 references were excluded against eligibility criteria. Thirty-nine articles were finally included in the systematic review. The results showed that constitutionally thin people seem to be underweight but not underfat and present a fat-free mass as blunted as anorexic patients, despite being a little less underweight. The meta-analysis confirmed that constitutionally thin people present normal energy intake and revealed a trend toward a higher resting metabolic rate to fat-free mass ratio which suggests a highly metabolic fat-free mass. Contrary to patients with anorexia nervosa, constitutionally thin people present normal levels of insulin-like growth factor 1, estradiol, growth hormone, follicle-stimulating hormone, and luteinizing hormone. An intermediate level of leptin between anorexic and control participants was however observed in constitutional thinness. While all the studies reported normal free triiodothyronine and cortisol levels in constitutionally thin individuals, a higher fasting free triiodothyronine level (p = 0.033) and a lower 24 h mean cortisol level (p = 0.005) were observed for the first time. Present results give robust evidence that constitutionally thin people present an atypical phenotype highly different from anorexia nervosa.

Equations for estimating the oxygen cost of walking in stroke patients: a systematic review

OBJECTIVE

To report all equations that can potentially be used to estimate the oxygen cost of walking (Cw) without using a respiratory gas exchange analyzer and to provide the level of reliability of each equation.

DATA SOURCES

Webline, Medline, Scopus, ScienceDirect, Bielefeld Academic Search Engine (BASE), and Wiley Online Library databases from 1950 to August 2019 with search terms related to stroke and oxygen cost of walking.

METHODS

This systematic review was reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, and the methodological quality of included studies was determined with the Critical Appraisal Skills Programme (CASP).

RESULTS

We screened 2065 articles, and 33 were included for full-text analysis. Four articles were included in the data synthesis (stroke individuals=184). Analysis reported 4 equations estimating Cw that were developed from logistic regression equations between Cw and self-selected walking speed. The equations differed in several methodological aspects (characteristics of individuals, type of equation, Cw reference measurement methods). The Compagnat et al. study had the highest quality (CASP score=9/9).

CONCLUSIONS

This literature review highlighted 4 equations for estimating Cw from self-selected walking speed. Compagnat et al. presented the best quality parameters, but this work involved a population restricted to individuals with hemispheric stroke sequelae.

Fluctuating asymmetry, a marker of poor growth quality, is associated with adult male metabolic rate

OBJECTIVES

Life history theory, a branch of evolutionary theory, predicts the existence of trade-offs in energetic allocation between competing physiological functions. The core metabolic cost of self-maintenance, measured by resting metabolic rate (RMR), represents a large component of human daily energy expenditure. Despite strong selective pressures for energetic frugality and high observed interindividual variation in RMR, the link between RMR and energetic allocation to life-history traits remains understudied in humans.

MATERIALS

In a sample of 105 (m = 57, f = 48), we investigated the relationship between adult RMR and investment in growth quality, as measured by fluctuating asymmetry (FA).

RESULTS

Measurement of RMR and FA in university rowers revealed a significant positive correlation amongst males (n = 57, r = 0.344, p = 0.005, 1-tailed; standardized 95% CI, 0.090 to 0.598). Convincing evidence for a correlation among females was not found (n = 48, r = 0.142, p = 0.169, 1-tailed, standardized 95% CI, -0.152 to 0.435).

DISCUSSION

The data suggest that low-quality asymmetrical growth is associated with later-life metabolic inefficiencies in males. Energetic investment in processes (likely concerning the stress-response) unrelated to growth during childhood may thereby trade-off against adult metabolic efficiency. We suggest that the presence of a relationship between RMR and FA in males but not females may be explained by the additional metabolic strain associated with larger body size and increased male muscularity, which may amplify the inefficiencies arising from low-quality growth.

Body composition helps: Differences in energy expenditure between pregnant and nonpregnant females

OBJECTIVES

Human pregnancy is associated with important physiological changes that usually increase energetic requirements. However, great variability exists in the costs and mechanisms required to bear pregnancy. Since body mass (BM) and composition are modified during gestation, it is of great interest to compare the influence of BM on energy expenditure (EE) in pregnant and nonpregnant females.

METHODS

BM, body composition, and EE of 77 volunteers (35 pregnant and 42 nonpregnant females) were measured. The pregnant volunteers completed two measurement rounds at 28 and 32 gestation weeks. Differences on the measured parameters were sought, and comparison of regression lines was computed to test how BM affected the EE of the volunteers.

RESULTS

BM and body composition parameters are significantly higher in pregnant females, but EE is not statistically different. Pregnant females have a larger percentage of fat mass, but lower percentage of fat-free mass (FFM). The EE per kg of FFM is similar in both groups. Comparison of regression lines shows that pregnancy does not change the relationship between BM and EE, but for similar BM pregnant females expend less energy than nonpregnant females.

CONCLUSIONS

We propose that their larger percentage of passive body tissues is the reason why pregnant females expend less energy than nonpregnant females of similar BM, without changing the scaling of EE on BM. Thus, pregnancy could not be as energetically constraining as usually assumed, with important consequences for human reproductive ecology.

Validity of Accelerometers for the Evaluation of Energy Expenditure in Obese and Overweight Individuals: A Systematic Review

OBJECTIVE

Even though the validity of accelerometers for the measurement of energy expenditure (EE) has been demonstrated for normal-weight individuals, the applicability of this instrument in obese individuals remains controversial. This review aims to summarize the level of agreement between accelerometers and the gold standards (indirect calorimetry and doubly labelled water) for the measurement of energy expenditure (EE) in obese or overweight individuals.

METHODS

The literature search was limited to comparison studies assessing agreement in EE determination between accelerometers and indirect calorimetry (IC) or doubly labelled water (DLW). We searched in PubMed and in Scopus until March 1, 2019. The analysis was restricted to obese or overweight adult individuals. The following descriptive information was extracted for each study: sample size, characteristics of participants (sex, age, BMI, fat mass percentage, any pathological conditions, modality of recruitment in the study, and exclusion criteria), accelerometer description (model, type and body position), and type of gold standard and validity protocol (duration, conditions, and requirements during and before the experiment). Three review authors independently screened the obtained results, and the quality of the selected articles was assessed by the QUADAS-2 tool.

RESULTS

We obtained seventeen eligible articles, thirteen of which showed concerns for the applicability section, due to the patient selection. Regarding the accelerometers, nine devices were validated in the included studies with the BodyMedia SenseWear® (SWA) being the most frequently validated. Although correlations between accelerometers and the gold standard were high in some studies, agreement between the two methods was low, as shown by the Bland-Altman plots.

CONCLUSIONS

Most accelerometer estimations of EE were inaccurate for obese/overweight subjects, and authors advise to improve the accuracy of algorithms for SWA software, or the predicted equations for estimating EE from other accelerometers.

Development of new predictive equations for basal metabolic rate in Iranian healthy adults: negligible effect of sex

Some studies have reported inaccuracy of predicting basal metabolic rate (BMR) by using common equations for Asian people. Thus, this study was undertaken to develop new predictive equations for the Iranian community and also to compare their accuracy with the commonly used formulas. Anthropometric measures and thyroid function were evaluated for 267 healthy subjects (18-60 y). Indirect calorimetry (InCal) was performed only for those participants with normal thyroid function tests (n = 252). Comparison of predicted RMR (both kcal/d and kcal.kg.wt^-1.d^-1) using current predictive formulas and measured RMR revealed that Harris-Benedict and FAO/WHO/UNU significantly over-estimated and Mifflin-St. Jeor significantly under-estimated RMR as compared to InCal measurements. In stepwise regression analysis for developing new equations, the highest r² (=0.89) was from a model comprising sex, height and weight. However, further analyses revealed that unlike the subjects under 30 y, the association between age and the measured RMR in subjects 30 y and plus was negative (r = -0.241, p = 0.001). As a result, two separate equations were developed for these two age groups. Over 80 percent of variations were covered by the new equations. In conclusion, there were statistical significant under- and over-estimation of RMR using common predictive equations in our subjects. Using the new equations, the accuracy of the calculated RMR increased remarkably.

Estimating energy expenditure of head-hauling water and grain grinding from heart rate monitor measurements in northern Mozambique

OBJECTIVE

Even though sub-Saharan African women spend millions of person-hours per day fetching water and pounding grain, to date, few studies have rigorously assessed the energy expenditure costs of such domestic activities. As a result, most analyses that consider head-hauling water or hand pounding of grain with a mortar and pestle (pilão use) employ energy expenditure values derived from limited research. The current paper compares estimated energy expenditure values from heart rate monitors v. indirect calorimetry in order to understand some of the limitations with using such monitors to measure domestic activities.

DESIGN

This confirmation study estimates the metabolic equivalent of task (MET) value for head-hauling water and hand-pounding grain using both indirect calorimetry and heart rate monitors under laboratory conditions.

SETTING

The study was conducted in Nampula, Mozambique.

PARTICIPANTS

Forty university students in Nampula city who recurrently engaged in water-fetching activities.

RESULTS

Including all participants, the mean MET value for head hauling 20 litres (20·5 kg, including container) of water (2·7 km/h, 0 % slope) was 4·3 (sd 0·9) and 3·7 (sd 1·2) for pilão use. Estimated energy expenditure predictions from a mixed model were found to correlate with observed energy expenditure (r2 0·68, r 0·82). Re-estimating the model with pilão use data excluded improved the fit substantially (r2 0·83, r 0·91).

CONCLUSIONS

The current study finds that heart rate monitors are suitable instruments for providing accurate quantification of energy expenditure for some domestic activities, such as head-hauling water, but are not appropriate for quantifying expenditures of other activities, such as hand-pounding grain.

Human athletic paleobiology; using sport as a model to investigate human evolutionary adaptation

The use of sport as a conceptual framework offers unprecedented opportunities to improve our understanding of what the body does, shedding new light on our evolutionary trajectory, our capacity for adaptation, and the underlying biological mechanisms. This approach has gained traction over recent years. To date, sport has facilitated exploration not only of the evolutionary history of our species as a whole, but also of human variation and adaptation at the interindividual and intraindividual levels. At the species level, analysis of lower and upper limb biomechanics and energetics with respect to walking, running and throwing have led to significant advances in the understanding of human adaptations relative to other hominins. From an interindividual perspective, investigation of physical activity patterns and endurance running performance is affording greater understanding of evolved constraints of energy expenditure, thermoregulatory energetics, signaling theory, and morphological variation. Furthermore, ultra-endurance challenges provoke functional trade-offs, allowing new ground to be broken in the study of life history trade-offs and human adaptability. Human athletic paleobiology-the recruitment of athletes as study participants and the use of contemporary sports as a model for studying evolutionary theory-has great potential. Here, we draw from examples in the literature to provide a review of how the use of athletes as a model system is enhancing understanding of human evolutionary adaptation.

No sex differences in the economy of load-carriage

OBJECTIVES

Load transport activities are of vital importance to current foragers for daily subsistence tasks; thus, it has been suggested that these practices have transformed physical and behavioral characteristics through human evolution. Together with the procurement targets and strategies, the transportation of resources acquired while foraging is strongly influenced by the sex of the foragers. In hunter-gatherer societies, women, despite their smaller body size, usually carry heavier burdens than males. In this study, whether those behavioral differences can be explained by a different economy of load-carriage by sex, irrespective of the body mass of the individuals, is investigated.

MATERIAL AND METHODS

The energy expenditure of a sample of 48 volunteers (21 females, 27 males) during a set of locomotion and burden transport trials was monitored. Two indexes were computed to compare the increment in the cost of locomotion relative to the load carried by sex.

RESULTS

The results demonstrate that both males and females, carrying the same relative loads, experience the same increment over the cost of their unloaded locomotion. Therefore, apart from obvious differences in body mass, there is no evidence of a dissimilar economy favoring one sex over the other that would explain the differences in load-carriage activities observed among current foraging populations.

CONCLUSIONS

These outcomes provide new conclusions about the constraints of the behavioral ecology of burden transport activities, and highlight the necessity to reevaluate, from an evolutionary perspective, the ideas about the sexual division of subsistence labor in hunter-gatherer and agriculturalist populations.

Evaluation of an activity monitor for use in pregnancy to help reduce excessive gestational weight gain

Background

Excessive weight gain during pregnancy increases the risk for negative effects on mother and child during pregnancy, delivery, and also postnatally. Excessive weight gain can be partially compensated by being sufficiently physically active, which can be measured using activity trackers. Modern activity trackers often use accelerometer data as well as heart rate data to estimate energy expenditure. Because pregnancy affects the metabolism and cardiac output, it is not evident that activity trackers that are calibrated to the general population can be reliably used during pregnancy. We evaluated whether an activity monitor designed for the general population is sufficiently accurate for estimating energy expenditure in pregnant women.

Methods

Forty pregnant women (age: 30.8 ± 4.7 years, BMI: 25.0 ± 4.0) from all three trimesters performed a 1-h protocol including paced and self-paced exercise activities as well as household activities. We tracked reference energy expenditure using indirect calorimetry and used equivalence testing to determine whether the estimated energy expenditure from the activity monitor was within the limits of equivalence.

Results

Overall we found an averaged underestimation of 10 kcal (estimated energy expenditure was 97% of the reference measurement). The 90% CI for the cumulative total energy expenditure was 94–100%. The activities of self-paced cycling, household activities, stair-walking, and yoga had one of their equivalence boundaries outside a 80–125% range of equivalence; for exercise on a cross-trainer, for self-paced and fixed-pace walking, fixed-paced cycling, and resting, the estimations were within the limits of equivalence.

Conclusions

We conclude that the activity monitor is sufficiently accurate for every-day use during pregnancy. The observed deviations can be accounted for and are acceptable from a statistical and an applied perspective because the positive and negative deviations that we observed cancel out to an accurate average energy expenditure over a day, and estimations during exercise are sufficiently accurate to enable coaching on physical activity. The positive and negative deviations themselves were relatively small. Therefore, the activity monitor can be used to help in preventing excessive weight gain during pregnancy by accurately tracking physical activity.

A trade-off between cognitive and physical performance, with relative preservation of brain function

Debate surrounds the issue of how the large, metabolically expensive brains of Homo sapiens can be energetically afforded. At the evolutionary level, decreased investment in muscularity, adiposity and the digestive tract allow for a larger brain. Developmentally, high neo-natal adiposity and preferential distribution of resources to the brain provide an energetic buffer during times of environmental stress. Through an experimental design, we investigated the hypothesis of a trade-off involving brain and muscle at the acute level in humans. Mental performance was measured by a free-recall test, and physical performance by power output on an indoor rowing ergometer. Sixty-two male student rowers performed the two tests in isolation, and then again simultaneously. Paired samples t-tests revealed that both power output and mental performance reduced when tested together compared to in isolation (t(61) = 9.699, p < 0.001 and t(61) = 8.975, p < 0.001). Furthermore, the decrease in physical performance was greater than the decrease in mental performance (t(61) = -2.069, p = 0.043). This is the first investigation to demonstrate an acute level trade-off between these two functions, and provides support for the selfish brain hypothesis due to the relative preservation of cognitive function over physical power output. The underlying mechanism is unclear, and requires further work.

No change in energy efficiency in lactation: Insights from a longitudinal study

OBJECTIVES

Lactation is the most energy-demanding phase of reproduction for human females, but it is still unclear how women in different environments are able to meet this additional energy demand. Previous studies have investigated whether changes in metabolism could have an energy-sparing effect in lactation, with conflicting results. Here, we asked whether increased energy efficiency in physical activity serves as an energy-sparing mechanism in lactation.

METHODS

We used a longitudinal design with a control group. Participants were 33 well-nourished, exclusively breastfeeding women and 29 non-pregnant, non-lactating (NPNL) controls aged 32 ± 4 years. Lactating women were measured at peak- and post-lactation. NPNL controls completed a baseline measurement and a follow-up visit. Energy efficiency in physical activity was assessed using a graded submaximal exercise test and calculated as delta efficiency (change in work accomplished over change in energy expended) and gross efficiency (work accomplished over energy expended).

RESULTS

There was no significant change in either delta efficiency or gross efficiency from peak to post lactation in lactating women, and no significant difference in delta efficiency between lactating women and NPNL controls at any time period. However, lactating women showed greater between-visit variation in delta efficiency than the NPNL controls. Additionally, 79% of lactating participants lost weight between visits (mean weight loss -3.6 ± 2.3kg), consistent with a mobilization of body tissues to support lactation.

CONCLUSION

We found no support for the idea that lactating women undergo an increase in energy efficiency to support the energy costs of lactation.

Measurement Methods for Physical Activity and Energy Expenditure: a Review

Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure. The benefits of physical activity for health maintenance have been well documented, especially in the prevention and management of chronic diseases. Therefore, accurate measurement of physical activity and energy expenditure is essential both for epidemiological studies and in the clinical context. Given the large number of available methods, it is important to have an understanding of each, especially when one needs to choose a technique to use. The purpose of this review was to discuss the components of total energy expenditure and present advantage and limitations of different methods of physical activity and energy expenditure assessment.

Carrying loads: Validating a portable tri-axial accelerometer during frequent and brief physical activity

OBJECTIVES

The aim of this study is to evaluate the validity of the SenseWear Armband™ (SWA, Model MF-SW, BodyMedia Inc.) as a tool to assess daily brief, light- to moderate-intensity activities.

DESIGN

A total of 41 volunteers were recruited (27 males, 14 females) to perform several trials, including a resting metabolic rate test and a number of walking trials while carrying different loads in a backpack.

METHODS

Energy expenditure during trials was measured using both the SWA™ mini device, with the indirect calorimetry method (MasterScreen CPX and Oxycon Mobile JAEGER™ devices) used for validated comparative measurement.

RESULTS

The SWA™ mini shows agreement with indirect calorimetry in all trials. However, the SWA™ mini over-estimated expenditure in all participants. Individual assessment estimates with the SWA™ mini also exhibited random errors. The variations in energy expenditure (EE) resulting from increased carried loads during the trials were not statistically significant when EE was measured with the SWA™ mini. Furthermore, Metabolic Equivalent of Task (MET) calculation, highly dependent on estimated energy expenditure per unit time, also was likely overestimated. In contrast, the SWA™ mini provided estimates of the resting metabolic rate with a small error.

CONCLUSIONS

The SWA™ mini is not a valid device for estimating energy expenditure in brief light- or moderate activities.

Validity of a population-specific BMR predictive equation for adults from an urban tropical setting

BACKGROUND & AIMS

Basal metabolic rate (BMR) is an important physiologic measure in nutrition research. In many instances it is not measured but estimated by predictive equations. The purpose of this study was to compare measured BMR (BMRm) with estimated BMR (BMRe) obtained by different equations.

METHODS

A convenient sample of 148 (89 women) 20-60 year-old subjects from the metropolitan area of Rio de Janeiro, Brazil participated in the study. BMRm values were measured by an indirect calorimeter and predicted by different equations (Schofield, Henry and Rees, Mifflin-St. Jeor and Anjos. All subjects had their body composition and anthropometric variables also measured. Accuracy of the estimations was established by the percentage of BMRe falling within ±10% of BMRm and bias when the 95% CI of the difference of BMRe and BMRm means did not include zero.

RESULTS

Mean BMRm values were 4833.5 (SD 583.3) and 6278.8 (SD 724.0) kJ*day^-1 for women and men, respectively. BMRe values were both biased and inaccurate except for values predicted by the Anjos equation. BMR overestimation was approximately 20% for the Schofield equation which was higher comparatively to the Henry and Rees (14.5% and 9.6% for women and men, respectively) and the Mifflin-St. Jeor (approximately 14.0%) equations. BMR estimated by the Anjos equation was unbiased (95% CI = -78.1; 96.3 kJ day^-1 for women and -282.6; 30.7 kJ*day^-1 for men).

CONCLUSIONS

Population-specific BMR predictive equations yield unbiased and accurate BMR values in adults from an urban tropical setting.

Birth weight predicted baseline muscular efficiency, but not response of energy expenditure to calorie restriction: An empirical test of the predictive adaptive response hypothesis

OBJECTIVES

Aiming to test the evolutionary significance of relationships linking prenatal growth conditions to adult phenotypes, this study examined whether birth size predicts energetic savings during fasting. We specifically tested a Predictive Adaptive Response (PAR) model that predicts greater energetic saving among adults who were born small.

METHODS

Data were collected from a convenience sample of young adults living in Albuquerque, NM (n = 34). Indirect calorimetry quantified changes in resting energy expenditure (REE) and active muscular efficiency that occurred in response to a 29-h fast. Multiple regression analyses linked birth weight to baseline and postfast metabolic values while controlling for appropriate confounders (e.g., sex, body mass).

RESULTS

Birth weight did not moderate the relationship between body size and energy expenditure, nor did it predict the magnitude change in REE or muscular efficiency observed from baseline to after fasting. Alternative indicators of birth size were also examined (e.g., low v. normal birth weight, comparison of tertiles), with no effects found. However, baseline muscular efficiency improved by 1.1% per 725 g (S.D.) increase in birth weight (P = 0.037).

CONCLUSIONS

Birth size did not influence the sensitivity of metabolic demands to fasting-neither at rest nor during activity. Moreover, small birth size predicted a reduction in the efficiency with which muscles convert energy expended into work accomplished. These results do not support the ascription of adaptive function to phenotypes associated with small birth size. © 2015 Wiley Periodicals, Inc. Am. J. Hum. Biol. 28:484-492, 2016. © 2015 Wiley Periodicals, Inc.

Resting metabolic rate varies by race and by sleep duration

OBJECTIVE

Short sleep duration is a significant risk factor for weight gain, particularly in African Americans and men. Increased caloric intake underlies this relationship, but it remains unclear whether decreased energy expenditure is a contributory factor. The current study assessed the impact of sleep restriction and recovery sleep on energy expenditure in African American and Caucasian men and women.

METHODS

Healthy adults participated in a controlled laboratory study. After two baseline sleep nights, subjects were randomized to an experimental (n = 36; 4 h sleep/night for five nights followed by one night with 12 h recovery sleep) or control condition (n = 11; 10 h sleep/night). Resting metabolic rate and respiratory quotient were measured using indirect calorimetry in the morning after overnight fasting.

RESULTS

Resting metabolic rate-the largest component of energy expenditure-decreased after sleep restriction (-2.6%, P = 0.032) and returned to baseline levels after recovery sleep. No changes in resting metabolic rate were observed in control subjects. Relative to Caucasians (n = 14), African Americans (n = 22) exhibited comparable daily caloric intake but a lower resting metabolic rate (P = 0.043) and higher respiratory quotient (P = 0.013) regardless of sleep duration.

CONCLUSIONS

Sleep restriction decreased morning resting metabolic rate in healthy adults, suggesting that sleep loss leads to metabolic changes aimed at conserving energy.

Validation of five minimally obstructive methods to estimate physical activity energy expenditure in young adults in semi-standardized settings

We compared the accuracy of five objective methods, including two newly developed methods combining accelerometry and activity type recognition (Acti4), against indirect calorimetry, to estimate total energy expenditure (EE) of different activities in semi-standardized settings. Fourteen participants performed a standardized and semi-standardized protocol including seven daily life activity types, while having their EE measured by indirect calorimetry. Simultaneously, physical activity was quantified by an ActivPAL³, two ActiGraph GT3X+’s and an Actiheart. EE was estimated by the standard ActivPAL³ software (ActivPAL), ActiGraph GT3X+ (ActiGraph) and Actiheart (Actiheart), and by a combination of activity type recognition via Acti4 software and activity counts per minute (CPM) of either a hip- or thigh-worn ActiGraph GT3X+ (AGhip + Acti4 and AGthigh + Acti4). At group level, estimated physical activities EE by Actiheart (MSE = 2.05) and AGthigh + Acti4 (MSE = 0.25) were not significantly different from measured EE by indirect calorimetry, while significantly underestimated by ActiGraph, ActivPAL and AGhip + Acti4. AGthigh + Acti4 and Actiheart explained 77% and 45%, of the individual variations in measured physical activity EE by indirect calorimetry, respectively. This study concludes that combining accelerometer data from a thigh-worn ActiGraph GT3X+ with activity type recognition improved the accuracy of activity specific EE estimation against indirect calorimetry in semi-standardized settings compared to previously validated methods using CPM only.

Assessment of physical activity and energy expenditure: an overview of objective measures

The ability to assess energy expenditure (EE) and estimate physical activity (PA) in free-living individuals is extremely important in the global context of non-communicable diseases including malnutrition, overnutrition (obesity), and diabetes. It is also important to appreciate that PA and EE are different constructs with PA defined as any bodily movement that results in EE and accordingly, energy is expended as a result of PA. However, total energy expenditure, best assessed using the criterion doubly labeled water (DLW) technique, includes components in addition to physical activity energy expenditure, namely resting energy expenditure and the thermic effect of food. Given the large number of assessment techniques currently used to estimate PA in humans, it is imperative to understand the relative merits of each. The goal of this review is to provide information on the utility and limitations of a range of objective measures of PA and their relationship with EE. The measures discussed include those based on EE or oxygen uptake including DLW, activity energy expenditure, physical activity level, and metabolic equivalent; those based on heart rate monitoring and motion sensors; and because of their widespread use, selected subjective measures.

BMR in a Brazilian adult probability sample: the Nutrition, Physical Activity and Health Survey

OBJECTIVE

To measure BMR in a probability sample of adults from an urban city of Brazil and to compare indirectly measured BMR (BMRi) with BMR predicted from different equations.

DESIGN

BMR data were obtained by indirect calorimetry and estimated by different predictive equations (Schofield; Harris and Benedict; Henry and Rees). Anthropometric and body composition measures were also obtained.

SETTING

The Nutrition, Physical Activity and Health Survey (PNAFS), a household survey conducted in Niterói, Rio de Janeiro state, Brazil.

SUBJECTS

Representative sample of 529 adults (aged ≥20 years; 339 females) living in Niterói, Rio de Janeiro state, Brazil.

RESULTS

Mean BMRi values were 5839.7 (se 73.9) kJ/d and 4758.1 (se 39.5) kJ/d for men and women, respectively. Predicted BMR by all equations was significantly higher (difference between means and 95% CI did not include zero) than BMRi in both men and women of all ages. Overall bias in BMR (predicted BMR minus BMRi) using the Schofield equations (overestimation of about 20%) was higher than when using the Henry and Rees equations (13% and 16% overestimation for males and females, respectively). The percentage of individuals whose BMR predicted by the Schofield equations fell within 10% of BMRi was very low (7.8% and 14.1% of males nd females, respectively).

CONCLUSIONS

Current available predictive equations of BMR are not adequate to estimate BMR in Brazilians living in Niterói, Rio de Janeiro, Brazil.

Measuring energy expenditure in clinical populations: rewards and challenges

The measurement of energy expenditure (EE) is recommended as an important component of comprehensive clinical nutrition assessments in patients with altered metabolic states, who failed to respond to nutrition support and with critical illness that require individualized nutrition support. There is evidence that EE is variable in patients with metabolic diseases, such as chronic renal disease, cirrhosis, HIV, cancer cachexia, cystic fibrosis and patients under intensive care. By using appropriate techniques and interpretations of basal or resting EE, clinicians can facilitate the adequate nutrition support with minimum negative impacts from under- or overfeeding in these patients. This review is based on our current understanding of the different components of EE and the techniques to measure them, and to re-examine advances and challenges to determine energy needs in clinical populations with more focuses on the obese, pediatric and elderly patients. In addition, technological advances have expanded the choices of market-available equipments for assessing EE, which also bring specific challenges and rewards in selecting the right equipment with specific performance criteria. Lastly, analytical considerations of interpreting the results of EE in the context of changing body composition are presented and discussed.

Cooperative breeding and maternal energy expenditure among Aka foragers

OBJECTIVES

Previous research among foragers and theory suggests that nonmaternal caregivers offer essential assistance, which supports female reproduction and the costs associated with lengthy child development. Mothers' face trade-offs in energy allocation between work and childcare, particularly when mothers have an infant. These trade-offs likely have crucial impacts on the pace of reproduction and child health. Caregivers can help mothers with childcare or they can reduce a mother's nonchildcare workload. If caregivers assist mothers by substituting childcare, then maternal energy expenditure (EE) in other work activities should increase. If caregivers assist mothers by substituting labor, then maternal EE in work activities should decrease when caregivers are present.

METHODS

Utilizing detailed, quantitative behavioral observations and EE data, we test these propositions with data from 28 Aka forager mothers with children <35 months old. We isolate paternal, grandmaternal, and other caregiver effects on maternal EE and childcare in multivariate analyses.

RESULTS

Our results show that caregivers (largely grandmothers) significantly reduce mothers' work EE by as much 216 kcal across a 9-hour observation period, while fathers and juveniles appear to increase maternal EE. Direct childcare from grandmothers decreases maternal direct care by about one-to-one indicating a labor substitution. Direct childcare from fathers decreases maternal care by almost 4 to 1, resulting in a net reduction of total direct care from all caregivers.

CONCLUSIONS

Our results indicate that there are multiple pathways by which helpers offset maternal work/childcare trade-offs.