Climate variables as predictors of basal metabolic rate: New equations

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.

Beyond skeletal studies: A computational analysis of nasal airway function in climate adaptation

OBJECTIVES

Ecogeographic variation in human nasal anatomy has historically been analyzed on skeletal morphology and interpreted in the context of climatic adaptations to respiratory air-conditioning. Only a few studies have analyzed nasal soft tissue morphology, actively involved in air-conditioning physiology.

MATERIALS AND METHODS

We used in vivo computer tomographic scans of (N = 146) adult individuals from Cambodia, Chile, Russia, and Spain. We conducted (N = 438) airflow simulations during inspiration using computational fluid dynamics to analyze the air-conditioning capacities of the nasal soft tissue in the inflow, functional, and outflow tract, under three different environmental conditions: cold-dry; hot-dry; and hot-humid. We performed statistical comparisons between populations and sexes.

RESULTS

Subjects from hot-humid regions showed significantly lower air-conditioning capacities than subjects from colder regions in all the three conditions, specifically within the isthmus region in the inflow tract, and the anterior part of the internal functional tract. Posterior to the functional tract, no differences were detected. No differences between sexes were found in any of the tracts and under any of the conditions.

DISCUSSION

Our statistical analyses support models of climatic adaptations of anterior nasal soft tissue morphology that fit with, and complement, previous research on dry skulls. However, our results challenge a morpho-functional model that attributes air-conditioning capacities exclusively to the functional tract located within the nasal cavity. Instead, our findings support studies that have suggested that both, the external nose and the intra-facial soft tissue airways contribute to efficiently warming and humidifying air during inspiration. This supports functional interpretations in modern midfacial variation and evolution.

The energetics of childhood: Current knowledge and insights into human variation, evolution, and health

How organisms capture and ultimately use metabolic energy-a limiting resource of life-has profound implications for understanding evolutionary legacies and current patterns of phenotypic variation, adaptation, and health. Energetics research among humans has a rich history in biological anthropology and beyond. The energetics of childhood, however, remains relatively underexplored. This shortcoming is notable given the accepted importance of childhood in the evolution of the unique human life history pattern as well as the known sensitivity of childhood development to local environments and lived experiences. In this review, I have three objectives: (1) To overview current knowledge regarding how children acquire and use energy, highlighting work among diverse human populations and pointing to recent advances and remaining areas of uncertainty; (2) To discuss key applications of this knowledge for understanding human variation, evolution, and health; (3) To recommend future avenues for research. A growing body of evidence supports a model of trade-offs and constraint in childhood energy expenditure. This model, combined with advancements on topics such as the energetics of immune activity, the brain, and the gut, provides insights into the evolution of extended human subadulthood and the nature of variation in childhood development, lifetime phenotype, and health.

Effects of long-term average temperature on cardiovascular disease hospitalizations in an American elderly population

BACKGROUND

Short-term exposure to high or low temperatures is associated with increased mortality and morbidity. Less is known about effects of long-term exposure to high or low temperatures. Prolonged exposure to high or low temperatures might contribute to pathophysiological mechanisms, thereby influencing the development of diseases. Our aim was to evaluate associations of long-term temperature exposure with cardiovascular disease (CVD) hospitalizations.

METHODS

We constructed an open cohort consisting of all fee-for-service Medicare beneficiaries, aged ≥65, living in the contiguous US from 2000 through 2016 (∼61.6 million individuals). We used data from the 4 km Gridded Surface Meteorological dataset to assess the summer (June-August) and winter (December-February) average daily maximum temperature for each year for each zip code. Cox-equivalent Poisson models were used to estimate associations with first CVD hospitalization, after adjustment for potential confounders. We performed stratified analyses to assess potential effect modification by sex, age, race, Medicaid eligibility and relative humidity.

RESULTS

Higher summer average and lower winter average temperatures were associated with an increased risk of CVD hospitalization. We found a HR of 1.068 (95% CI: 1.063, 1.074) per IQR increase (5.2 °C) for summer average temperature and a HR of 1.022 (95% CI: 1.017, 1.028) per IQR decrease (11.7 °C) for winter average temperature. Positive associations of higher summer average temperatures were strongest for individuals aged <75 years, Medicaid eligible, and White individuals. Positive associations of lower winter average temperatures were strongest for individuals aged <75 years and Black individuals, and individuals living in low relative humidity areas.

CONCLUSIONS

Living in areas with high summer average temperatures or low winter average temperatures could increase the risk of CVD hospitalizations. The magnitude of the associations of summer and winter average temperatures differs by demographics and relative humidity levels.

New insights into the variability of upper airway morphology in modern humans

The biological adaptation of the human lineage to its environment is a recurring question in paleoanthropology. Particularly, how eco-geographic factors (e.g., environmental temperature and humidity) have shaped upper airway morphology in hominins have been subject to continuing debate. Nasal shape is the result of many intertwined factors that include, but are not limited to, genetic drift, sexual selection, or adaptation to climate. A quantification of nasal airway (NA) morphological variation in modern human populations is crucial to better understand these multiple factors. In the present research, we study 195 in vivo CT scans of adult individuals collected in five different geographic areas (Chile, France, Cambodia, Russia, and South Africa). After segmentation of the nasal airway, we reconstruct 3D meshes that are analyzed with a landmark-free geometric morphometrics method based on surface deformation. Our results highlight subtle but statistically significant morphological differences between our five samples. The two morphologically closest groups are France and Russia, whose NAs are longer and narrower, with an important protrusion of the supero-anterior part. The Cambodian sample is the most morphologically distinct and clustered sample, with a mean NA that is wider and shorter. On the contrary, the Chilean sample form the most scattered cluster with the greatest intra-population variation. The South African sample is morphologically close to the Cambodian sample, but also partially overlaps the French and Russian variation. Interestingly, we record no correlation between NA volume and geographic groups, which raises the question of climate-related metabolic demands for oxygen consumption. The other factors of variation (sex and age) have no influence on the NA shape in our samples. However, NA volume varies significantly according both to sex and age: it is higher in males than in females and tends to increase with age. In contrast, we observe no effect of temperature or humidity on NA volume. Finally, we highlight the important influence of asymmetries related to nasal septum deviations in NA shape variation.

The predictive equations of resting metabolic rate for T ibetan adolescents aged 13–18 in T ibet, C hina

OBJECTIVES

The resting metabolic rate (RMR) predictive equations suitable for Tibetan adolescents in Tibet, China, were developed to provide a reference for their reasonable energy intake.

METHODS

We measured RMR by indirect calorimetry and body composition by bioelectrical impedance analysis in 325 Tibetan adolescents aged 13-18 years in Tibet, China. Stepwise regression analysis was used to develop the predictive equations. Pearson correlation analysis, paired sample t test, bias rate, concordance correlation coefficient (CCC) and Bland-Altman were used to verify the validity of the predictive equations.

RESULTS

The R² of Model 8 (0.642) was larger than Model 2 (boys, 0.642; girls, 0.533) and Model 7 (0.540), and Model 10 (0.534) was larger than Model 4 (boys, 0.531; girls, 0.443) and Model 9 (0.477).Compared with the existing predictive equations, the correlation (0.68-0.84) between the predicted values and the measured values, CCC (0.74-0.81) and consistency (Similar proportions within the upper and lower limits but lower differences) were higher and the bias rate (-1.0% to -2.5%) and root mean square error (207.4-263.7 kcal/day) were lower in this study. By comprehensive comparison, Model 8 and Model 10 were more valid.

CONCLUSIONS

The existing predictive equations cannot accurately predict the RMR of Tibetan adolescents in Tibet, China. In this study, the age segmentation predictive equations with age, sex, and fat free mass (FFM) as independent variables were more valid. The predictive equations were as follows: RMR (kcal/day) = 50.1 × FFM (kg) - 202.8 × Sex (F: 0; M: 1) - 72.1 × Age + 930.3, 13-15 years; RMR (kcal/day) = 58.4 × FFM (kg) - 441.1 × Sex (F: 0; M: 1) - 702.2, 16-18 years.

No association of BMI and body adiposity with cardiometabolic biomarkers among a small sample of reindeer herders of sub-Arctic Finland

The rising global obesity rate is alarming due to its real health and socioeconomic consequences. Finland, like other circumpolar regions, is also experiencing a rise in obesity . Here we assess BMI, body adiposity, and measures of cardiometabolic health among a small population of reindeer herders in sub-Arctic Finland. We collected anthropometric and biomarker measures at two different time points: October 2018 (N = 20) and January 2019 (N = 21) with a total of 25 unique individuals across the data collection periods (ages 20-64). Anthropometric measures included height, weight, age, and body composition. Biomarkers included measures of cholesterol, fasting glucose, HDL cholesterol, LDL cholesterol, and triglyceride levels. Over 70% of this sample was classified as "overweight" and "obese" as categorised by BMI and 64% classified as "overfat" based on body fat percentage. However, there was no significant relationship between BMI and body fat percentage with any of the measured biomarkers. Although the sample size is small, the results of this study suggest there might not be a strong correlation between BMI, body adiposity, and cardiometabolic health indices within this population - a pattern that has been documented elsewhere. However, further study is needed to confirm this lack of a correlation.

Basal metabolic rate and risk of multiple sclerosis: a Mendelian randomization study

To determine the relationship between basal metabolic rate (BMR) and multiple sclerosis (MS) susceptibility, we analyzed genome-wide association study (GWAS) summary statistics data from the International Multiple Sclerosis Genetics Consortium on a total of 115,803 participants of European descent, including 47,429 patients with MS and 68,374 controls. We selected 378 independent genetic variants strongly associated with BMR in a GWAS involving 454,874 participants as instrumental variables to examine a potential causal relationship between BMR and MS. A genetically predicted higher BMR was associated with a greater risk of MS (odds ratio [OR]: 1.283 per one standard deviation increase in BMR, 95% confidence interval [CI]: 1.108-1.486, P = 0.001). Moreover, we used the lasso method to eliminate heterogeneity (Q statistic = 384.58, P = 0.370). There was no pleiotropy in our study and no bias was found in the sensitivity analysis using the leave-one-out test. We provide novel evidence that a higher BMR is an independent causal risk factor in the development of MS. Further work is warranted to elucidate the potential mechanisms.

Combining adaptive and heat balance models for thermal sensation prediction: A new approach towards a theory and data-driven adaptive thermal heat balance model

The adaptive thermal heat balance (ATHB) framework introduced a method to account for the three adaptive principals, namely physiological, behavioral, and psychological adaptation, individually within existing heat balance models. This work presents a more detailed theoretical framework together with a theory-driven empirical determination toward a new formulation of the ATHB_PMV . The empirical development followed a rigor statistical process known from machine learning approaches including training, validation, and test phase and makes use of a subset (N = 57 084 records) of the ASHRAE Global Thermal Comfort Database. Results show an increased predictive performance among a wide range of outdoor climates, building types, and cooling strategies of the buildings. Furthermore, individual findings question the common believe that psychological adaptation is highest in naturally ventilated buildings. The framework offers further opportunities to include a variety of context-related variables as well as personal characteristics into thermal prediction models, while keeping mathematical equations limited and enabling further advancements related to the understanding of influences on thermal perception.

Reindeer herders from subarctic Finland exhibit high total energy expenditure and low energy intake during the autumn herd roundup

OBJECTIVE

High levels of total energy expenditure (TEE, kcal/day) have been documented among numerous human populations such as tropical climate horticulturalists and high-altitude agriculturalists. However, less work has been conducted among highly physically active cold climate populations.

METHODS

In October 2018, TEE was measured using the doubly labeled water (TEE_DLW , N = 10) and flex-heart rate methods (TEE_HR , N = 24) for 6-14 days among reindeer herders (20-62 years) in northern Finland during an especially physically demanding, but not seasonally representative, period of the year for herders-the annual reindeer herd roundup. Self-reported dietary intake was also collected during TEE measurement periods. TEE was then compared to that of hunter gatherer, farming, and market economies.

RESULTS

During the herd roundup, herders expended a mean of 4183 ± 949 kcal/day as measured by the DLW method, which was not significantly different from TEE_HR . Mean caloric intake was 1718 ± 709 kcal/day, and was significantly lower than TEE_DLW and TEE_HR (p < .001). Herder TEE_DLW was significantly higher than that of hunter gatherer (p = .0014) and market (p < .0014) economy populations; however, herder TEE_DLW was not different from that of farming populations (p = .91).

CONCLUSION

High TEE and low caloric intake among herders reflect the extreme demands placed on herders during the annual herd round up. Although TEE_DLW was similar between cold climate herders and hot climate farming populations, there are likely differences in how that TEE is comprised, reflecting the local ecologies of these populations.

Between a rock and a cold place: Neanderthal biocultural cold adaptations

A large body of work focuses on the unique aspects of Neanderthal anatomy, inferred physiology, and behavior to test the assumption that Neanderthals were hyper-adapted to living in cold environments. This research has expanded over the years to include previously unexplored and potentially adaptive features such as brown adipose tissue and fire-usage. Here we review the current state of knowledge of Neanderthal cold adaptations along morphological, physiological, and behavioral lines. While highlighting foundational as well as recent work, we also emphasize key areas for future research. Despite thriving in a variety of climates, it is well-accepted that Neanderthals appear to be the most cold-adapted of known fossil hominin groups; however, there are still many unknowns. There is a great deal yet to be uncovered about the nature and manifestation of Neanderthal adaptation and how the synergy of biology and culture helped buffer them against extreme and variable environments.

Shivering in the Pleistocene. Human adaptations to cold exposure in Western Europe from MIS 14 to MIS 11

During the mid-Middle Pleistocene MIS 14 to MIS 11, humans spread through Western Europe from the Mediterranean peninsulas to the sub-Arctic region, and they did so not only during the warm periods but also during the glacial stages. In doing so, they were exposed to harsh environmental conditions, including low or extremely low temperatures. Here we review the distribution of archeological assemblages in Western Europe from MIS 14 to MIS 11 and obtain estimates of the climatic conditions at those localities. Estimates of the mean annual temperature, mean winter and summer temperatures, and the lowest temperature of the coldest month for each locality were obtained from the Oscillayers database. Our results show that hominins endured cold exposure not only during the glacial stages but also during the interglacials, with winter temperatures below 0 °C at many localities. The efficacy of the main physiological and behavioral adaptations that might have been used by the Middle Pleistocene hominins to cope with low temperatures is evaluated using a simple heat-loss model. Our results suggest that physiological and anatomical adaptations alone, such as increasing basal metabolic rate and subcutaneous adipose tissue, were not enough to tolerate the low winter temperatures of Western Europe, even during the MIS 13 and MIS 11 interglacials. In contrast, the use of a simple fur bed cover appears to have been an extremely effective response to low temperatures. We suggest that advanced fire production and control technology were not necessary for the colonization of northern Europe during MIS 14 and MIS 12. We propose that Middle Pleistocene European populations were able to endure the low temperatures of those glacial stages combining anatomical and physiological adaptations with behavioral responses, such as the use of shelter and simple fur clothes.

Lack of a relationship between vitamin D status and resting metabolic rate in Iranian adults

OBJECTIVES

Studies suggest a positive relationship between 25-hydroxy vitamin D (25(OH)D)) and resting metabolic rate (RMR). We aimed to determine whether this relationship was also true of populations with very low vitamin D status.

METHODS

Fat mass (FM) and fat free mass (FFM) were determined from multifrequency bioimpedance analysis (InBody 720, Korea). RMR was based on indirect calorimetry (Cortex Metalyser 3B, Germany). Fasting blood measurements of 25(OH)D concentration, glucose and triglycerides were measured. Data were analyzed separately on men and women by tertile of vitamin D status and multiple linear regression analysis.

RESULTS

Two hundred and sixty-three subjects (115 males; 148 females) with a mean age of 37 years and mean %body fat of 30.5% were studied. In women but not men, age, body weight, waist circumference, FM, and FFM increased significantly across tertiles of 25(OH)D. However, there was no difference in unadjusted or adjusted RMR across tertiles of 25OHD in both women and men. Stepwise forward regression analysis showed that age and FFM in men, age and FM in women but not by 25(OH)D, were determinants of RMR. In addition, RMR adjusted for age, sex, FM, FFM and triglyceride-glucose index did not relate to 25(OH)D when linear (r = 0, P = .98), quadratic (r = 0.008, P = .34), or cubic (r = 0.010, P = .43) relationships were tested.

CONCLUSIONS

Residual variation in RMR did not relate to vitamin D status in a group of Iranian adults with very low vitamin D status. Future studies could examine whether such a relationship holds true, after the normalization of vitamin D status.

The ongoing nutrition transition thwarts long-term targets for food security, public health and environmental protection

The nutrition transition transforms food systems globally and shapes public health and environmental change. Here we provide a global forward-looking assessment of a continued nutrition transition and its interlinked symptoms in respect to food consumption. These symptoms range from underweight and unbalanced diets to obesity, food waste and environmental pressure. We find that by 2050, 45% (39-52%) of the world population will be overweight and 16% (13-20%) obese, compared to 29% and 9% in 2010 respectively. The prevalence of underweight approximately halves but absolute numbers stagnate at 0.4-0.7 billion. Aligned, dietary composition shifts towards animal-source foods and empty calories, while the consumption of vegetables, fruits and nuts increases insufficiently. Population growth, ageing, increasing body mass and more wasteful consumption patterns are jointly pushing global food demand from 30 to 45 (43-47) Exajoules. Our comprehensive open dataset and model provides the interfaces necessary for integrated studies of global health, food systems, and environmental change. Achieving zero hunger, healthy diets, and a food demand compatible with environmental boundaries necessitates a coordinated redirection of the nutrition transition. Reducing household waste, animal-source foods, and overweight could synergistically address multiple symptoms at once, while eliminating underweight would not substantially increase food demand.

Constraint and trade-offs regulate energy expenditure during childhood

Children's metabolic energy expenditure is central to evolutionary and epidemiological frameworks for understanding variation in human phenotype and health. Nonetheless, the impact of a physically active lifestyle and heavy burden of infectious disease on child metabolism remains unclear. Using energetic, activity, and biomarker measures, we show that Shuar forager-horticulturalist children of Amazonian Ecuador are ~25% more physically active and, in association with immune activity, have ~20% greater resting energy expenditure than children from industrial populations. Despite these differences, Shuar children's total daily energy expenditure, measured using doubly labeled water, is indistinguishable from industrialized counterparts. Trade-offs in energy allocation between competing physiological tasks, within a constrained energy budget, appear to shape childhood phenotypic variation (e.g., patterns of growth). These trade-offs may contribute to the lifetime obesity and metabolic health disparities that emerge during rapid economic development.

Physical activity and time budgets of Hadza forager children: Implications for self-provisioning and the ontogeny of the sexual division of labor

OBJECTIVES

To determine the effects of age and sex on physical activity and time budgets of Hadza children and juveniles, 5-14 years old, including both in-camp and out-of-camp activities.

METHODS

Behavioral data were derived from ~15 000 hourly in-camp scan observations of 76 individuals and 13 out-of-camp focal follows on nine individuals. The data were used to estimate energy expended and percentage of time engaged in a variety of routine activities, including food collection, childcare, making and repairing tools, and household maintenance.

RESULTS

Our results suggest that (1) older children spend more time in economic activities; (2) females spend more time engaged in work-related and economic activities in camp, whereas males spend more time engaged in economic activities out of camp; and (3) foraging by both sexes tends to net caloric gains despite being energetically costly.

CONCLUSIONS

These results show that, among the Hadza, a sexual division of labor begins to emerge in middle childhood and is well in place by adolescence. Furthermore, foraging tends to provide net caloric gains, suggesting that children are capable of reducing at least some of the energetic burden they place upon their parents or alloparents. The findings are relevant to our understanding of the ways in which young foragers allocate their time, the development of sex-specific behavior patterns, and the capacity of children's work efforts to offset the cost of their own care in a cooperative breeding environment.

Evaluation of thermal indices for their applicability in obstacle-resolving meteorology models

A thermally comfortable design of outdoor spaces favors social interaction and outdoor activities and thus contributes to the overall well-being of urban dwellers. To assess such a design, obstacle-resolving models (ORM) combined with thermal indices may be used. This paper reviews existing thermal indices to identify those suitable for thermal comfort assessment with ORMs. For the identification, 11 criteria and six index features are derived from literature analysis focusing on the characteristics of human environmental heat exchange, of outdoor urban environments, and of ORMs. An air temperature weighted world population distribution is calculated to derive the minimal air temperature range; a thermal index should cover to be applicable to 95% of the world population. The criteria are applied to 165 thermal indices by reviewing their original publications. Results show that only four thermal indices are suitable to be applied globally in their current form to various outdoor urban environments and also fulfill the requirements of ORMs. The evaluation of the index features shows that they differ with respect to the comprehensiveness of the thermophysiological model, the assessed human response, the treatment of clothing and activity, and the computational costs. Furthermore, they differ in their total application frequency in past ORM studies and in their application frequency for different climatic zones, as a systematic literature analysis of thermal comfort studies employing ORMs showed. By depicting the differences of the thermal indices, this paper provides guidance to select an appropriate thermal index for thermal comfort studies with ORMs.

Influence of nutritional status on basal metabolic rates among rural agriculturalists of Ngilo-Ilo, East Java

OBJECTIVES

Previous research has shown that tropical island populations have reduced basal metabolic rates (BMR) associated with the joint influences of heat stress and undernutrition. This study examines variation in BMR among an indigenous population of Indonesia, and compares these data with those collected from earlier studies in Indonesia.

METHODS

Anthropometric dimensions and BMR were measured on a sample of 35 Indonesian adults (28 men, 7 women) from the rural village of Ngilo-Ilo, East Java.

RESULTS

Mean measured BMRs (±SD) were 1433 ± 344 kcal/d in men and 1256 ±257 kcal/d in women, and were not significantly different from estimates using the FAO/WHO/UNU predictive questions. Underweight individuals (BMIs <18.5 kg/m² ) had BMRs that were 7.6% below predicted levels, while those with BMIs ≥18.5 kg/m² had BMRs that were 8.0% above predicted levels (P < .01). Underweight individuals also had significantly higher respiratory quotients (RQ = .94 vs. .89; P < .05), suggesting lower levels of fat oxidation. Compared to data from previous studies (1929-1979), men of the Ngilo-Ilo sample had similar BMIs (19.8 vs. 19.2 kg/m² ), but higher BMRs, after adjusting for age and body weight (+2.1% vs. -5.6%; P < .05).

CONCLUSIONS

Among the agriculturalists of Ngilo-Ilo, measured BMRs were low, but not significantly different from those predicted by the FAO/WHO/UNU equations. Among subjects of this sample and from earlier studies, poorer physical nutritional status was associated with reduced BMRs. These results suggest that chronic energy stress has consistently shaped metabolic function among Indonesian rural populations.

Decreased thermal sweating of central sudomotor mechanism in African and Korean men

OBJECTIVE

Tropical natives sweat less and preserve more body fluid than temperate natives, tolerating heat stress. However, the mechanisms involved in such sweating reduction have not been fully elucidated. We examined the sudomotor responses of men of African (n = 36) and Korean (n = 41) ancestry during hot water (43 °C) leg immersion (central sudomotor response). Correlations between mean body temperature, basal metabolic rate (BMR), and sweat rate were also examined.

METHODS

All procedures were done in an automated climate chamber. Local skin temperatures and BMR were measured and mean body temperature was calculated. Sweating activities which include evaporative loss rate, sweat onset time, sweat rate, sweat volume, and whole-body sweat loss volume were examined.

RESULTS

In the heat load test, Africans showed lower mean body and local skin temperatures than Koreans before and after heating. Before and after heating, BMR declined significantly in Africans, while that of Koreans declined less. Local sweat onset time increased more in Africans than in Koreans. Local evaporative loss rate, local sweat volume, local sweat rate, and whole body sweat loss volume were reduced in Africans compared with Koreans. There were positive associations of mean body temperature and resting BMR with mean sweat rate.

CONCLUSION

In conclusion, we observed a larger reduction of sudomotor activity in tropical Africans than in temperate Koreans, which was associated with their lower mean body temperature and lower resting BMR.

High resting metabolic rate among Amazonian forager-horticulturalists experiencing high pathogen burden

OBJECTIVES

Resting metabolic rate (RMR) reflects energetic costs of homeostasis and accounts for 60 to 75% of total energy expenditure (TEE). Lean mass and physical activity account for much RMR variability, but the impact of prolonged immune activation from infection on human RMR is unclear in naturalistic settings. We evaluate the effects of infection on mass-corrected RMR among Bolivian forager-horticulturalists, and assess whether RMR declines more slowly with age than in hygienic sedentary populations, as might be expected if older adults experience high pathogen burden.

MATERIALS AND METHODS

RMR was measured by indirect calorimetry (Fitmate MED, Cosmed) in 1,300 adults aged 20 to 90 and TEE was measured using doubly labeled water (n = 40). Immune biomarkers, clinical diagnoses, and anthropometrics were collected by the Tsimane Health and Life History Project.

RESULTS

Tsimane have higher RMR and TEE than people in sedentary industrialized populations. Tsimane RMR is 18 to 47% (women) and 22 to 40% (men) higher than expected using six standard prediction equations. Tsimane mass-corrected TEE is similarly elevated compared to Westerners. Elevated leukocytes and helminths are associated with excess RMR in multivariate regressions, and jointly result in a predicted excess RMR of 10 to 15%. After age 40, RMR declines by 69 kcal/decade (p < .0001). Controlling for lean mass and height accounts for 71% of age-related RMR decline, and adding indicators of infection minimally affects the age slope. The residual level of age-related decline from age 40 is 1.2% per decade.

CONCLUSION

High pathogen burden may lead to higher metabolic costs, which may be offset by smaller body mass or other energy-sparing mechanisms.

Basis for the gain and subsequent dilution of epidermal pigmentation during human evolution: The barrier and metabolic conservation hypotheses revisited

The evolution of human skin pigmentation must address both the initial evolution of intense epidermal pigmentation in hominins, and its subsequent dilution in modern humans. While many authorities believe that epidermal pigmentation evolved to protect against either ultraviolet B (UV-B) irradiation-induced mutagenesis or folic acid photolysis, we hypothesize that pigmentation augmented the epidermal barriers by shifting the UV-B dose-response curve from toxic to beneficial. Whereas erythemogenic UV-B doses produce apoptosis and cell death, suberythemogenic doses benefit permeability and antimicrobial function. Heavily melanized melanocytes acidify the outer epidermis and emit paracrine signals that augment barrier competence. Modern humans, residing in the cooler, wetter climes of south-central Europe and Asia, initially retained substantial pigmentation. While their outdoor lifestyles still permitted sufficient cutaneous vitamin D3 (VD3) synthesis, their marginal nutritional status, coupled with cold-induced caloric needs, selected for moderate pigment reductions that diverted limited nutritional resources towards more urgent priorities (=metabolic conservation). The further pigment-dilution that evolved as humans reached north-central Europe (i.e., northern France, Germany), likely facilitated cutaneous VD3 synthesis, while also supporting ongoing, nutritional requirements. But at still higher European latitudes where little UV-B breaches the atmosphere (i.e., present-day UK, Scandinavia, Baltic States), pigment dilution alone could not suffice. There, other nonpigment-related mutations evolved to facilitate VD3 production; for example, in the epidermal protein, filaggrin, resulting in reduced levels of its distal metabolite, trans-urocanic acid, a potent UV-B chromophore. Thus, changes in human pigmentation reflect a complex interplay between latitude, climate, diet, lifestyle, and shifting metabolic priorities.

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.

Influence of lower limb configuration on walking cost in Late Pleistocene humans

It has been proposed that Neandertals had about 30% higher gross cost of transport than anatomically modern humans (AMH) and that such difference implies higher daily energy demands and reduced foraging ranges in Neandertals. Thus, reduced walking economy could be among the factors contributing to the Neandertals' loss in competition with their anatomically modern successors. Previously, Neandertal walking cost had been estimated from just two parameters and based upon a pooled-sex sample. In the present study, we estimate sex-specific walking cost of Neandertals using a model accounting for body mass, lower limb length, lower limb proportions, and other features of lower limb configuration. Our results suggest that Neandertals needed more energy to walk a given distance than did AMH but the difference was less than half of that previously estimated in males and even far less pronounced in females. In contrast, comparison of the estimated walking cost adjusted to body mass indicates that Neandertals spent less energy per kilogram of body mass than AMH thanks to their lower limb configuration, males having 1-5% lower and females 1-3% lower mass-specific net cost of transport than AMH of the same sex. The primary cause of high cost of transport in Neandertal males is thus their great body mass, possibly a consequence of adaptation to cold, which was not fully offset by their cost-moderating lower limb configuration. The estimated differences in absolute energy spent for locomotion between Neandertal and AMH males would account for about 1% of previously estimated daily energy expenditure of Neandertal or AMH males.

Ontogenetic scaling of the human nose in a longitudinal sample: implications for genus Homo facial evolution

Researchers have hypothesized that nasal morphology, both in archaic Homo and in recent humans, is influenced by body mass and associated oxygen consumption demands required for tissue maintenance. Similarly, recent studies of the adult human nasal region have documented key differences in nasal form between males and females that are potentially linked to sexual dimorphism in body size, composition, and energetics. To better understand this potential developmental and functional dynamic, we first assessed sexual dimorphism in the nasal cavity in recent humans to determine when during ontogeny male-female differences in nasal cavity size appear. Next, we assessed whether there are significant differences in nasal/body size scaling relationships in males and females during ontogeny. Using a mixed longitudinal sample we collected cephalometric and anthropometric measurements from n = 20 males and n = 18 females from 3.0 to 20.0+ years of age totaling n = 290 observations. We found that males and females exhibit similar nasal size values early in ontogeny and that sexual dimorphism in nasal size appears during adolescence. Moreover, when scaled to body size, males exhibit greater positive allometry in nasal size compared to females. This differs from patterns of sexual dimorphism in overall facial size, which are already present in our earliest age groups. Sexually dimorphic differences in nasal development and scaling mirror patterns of ontogenetic variation in variables associated with oxygen consumption and tissue maintenance. This underscores the importance of considering broader systemic factors in craniofacial development and may have important implications for the study of patters craniofacial evolution in the genus Homo.

Laboratory and field methods for measuring human energy expenditure

Energetics research is central to the field of human biology. Energy is an important currency for measuring adaptation, because both its acquisition and allocation for biological processes have important implications for survival and reproduction. Recent technological and methodological advances are now allowing human biologists to study variation in energy dynamics with much greater accuracy in a wide variety of ecological contexts. This article provides an overview of the methods used for measuring human energy expenditure (EE) and considers some of the important ecological and evolutionary questions that can be explored from an energetics perspective. Basic principles of calorimetry are first presented, followed by an overview of the equipment used for measuring human EE and work capacity. Methods for measuring three important dimensions of human EE-resting metabolic rate, working/exercising EE, and total EE-are then presented, highlighting key areas of ongoing research.

Dietary intakes assessed by 24-h recalls in peri-urban African adolescents: validity of energy intake compared with estimated energy expenditure

BACKGROUND/OBJECTIVE

The objective of this study is to determine the relative validity of reported energy intake (EI) derived from multiple 24-h recalls against estimated energy expenditure (EE(est)). Basal metabolic rate (BMR) equations and physical activity factors were incorporated to calculate EE(est).

SUBJECTS/METHODS

This analysis was nested in the multidisciplinary PhysicaL Activity in the Young study with a prospective study design. Peri-urban black South African adolescents were investigated in a subsample of 131 learners (87 girls and 44 boys) from the parent study sample of 369 (211 girls and 158 boys) who had all measurements taken. Pearson correlation coefficients and Bland-Altman plots were calculated to identify the most accurate published equations to estimate BMR (P<0.05 statistically significant). EE(est) was estimated using BMR equations and estimated physical activity factors derived from Previous Day Physical Activity Recall questionnaires. After calculation of EE(est), the relative validity of reported energy intake (EI(rep)) derived from multiple 24-h recalls was tested for three data subsets using Pearson correlation coefficients. Goldberg's formula identified cut points (CPs) for under and over reporting of EI.

RESULTS

Pearson correlation coefficients between calculated BMRs ranged from 0.97 to 0.99. Bland-Altman analyses showed acceptable agreement (two equations for each gender). One equation for each gender was used to calculate EE(est). Pearson correlation coefficients between EI(rep) and EE(est) for three data sets were weak, indicating poor agreement. CPs for physical activity groups showed under reporting in 87% boys and 95% girls.

CONCLUSION

The 24-h recalls measured at five measurements over 2 years offered poor validity between EI(rep) and EE(est).