Measurements Of Basal Metabolic Rate Research Articles

Effect of Endogenous Hormone Levels on Basal Metabolic Rate in Men With Obesity.

Basal metabolic rate (BMR) is an important factor in weight management and is influenced by fat-free mass (FFM), fat mass (FM) and age. Current knowledge of the influence of hormonal levels on BMR is based on studies with small populations, studies that investigate exogenous administration and studies frequently lacking correction for body composition. Cross-sectional study. All men (n = 457) who were referred to our centre for a metabolic work-up were eligible for inclusion. Median age was 47 (18-78) years and the vast majority had obesity (BMI ≥ 30 kg/m², 90.9%). All men had a measurement of BMR, body composition and measurement of testosterone, sex hormone binding globulin (SHBG), dehydroepiandrosterone sulphate (DHEAS), insulin-like growth factor 1 (IGF-1), thyroid-stimulating hormone (TSH) and free thyroxine (fT4). Men with low, normal and/or high levels of each of these hormones were compared. The association between hormone levels and BMR was assessed through linear regression models. All analyses were controlled for FFM, FM and age. In men with obesity, testosterone (total or free) was not associated with BMR. Linear regression analysis showed that DHEAS was positively associated with BMR in a sample of men with obesity and normal endogenous DHEAS levels, with the following equation: BMR (adjusted R² = 0.72): (BMR [kcal/d] = 513.402 + 18.940 × FFM [kg] + 9.507 × FM [kg] - 3.362 × age [years] + 0.307 × DHEAS [µg/dL]) (p < 0.01). TSH, fT4 and IGF-1 were not associated with BMR. In men with obesity, endogenous DHEAS is positively associated with BMR. Testosterone, TSH, fT4 and IGF-1 were not associated with BMR in men with obesity. Since we examined the specific population of men with obesity and only examined endogenous hormone levels, no extrapolation of results to other populations or the overall population can be made.

Comparative analysis of basal metabolic rate measurement methods in overweight and obese individuals: A retrospective study.

The global prevalence of overweight and obesity is on the rise, presenting significant health challenges worldwide. Obesity is associated with various chronic diseases and imposes substantial economic burdens on society. Accurate assessment of basal metabolic rate (BMR) is crucial for effective weight management strategies. This retrospective study, conducted at Baskent University Hospital between October 2019 and October 2023, analyzed data from 133 overweight and obese individuals. Various methods including indirect calorimetry (IC), predictive equations (Harris-Benedict and Mifflin-St Jeor), and bioelectrical impedance analysis (BIA) were used to estimate BMR. Additionally, demographic, clinical, and body composition data were recorded. The mean BMR measured using IC was 1581 ± 322 kcal/day, which was significantly lower than the BMR estimated by other methods such as BIA (1765.8 ± 344.09 kcal/day), Harris-Benedict (1787.64 ± 341.4 kcal/day), and Mifflin-St Jeor equations (1690.08 ± 296.36 kcal/day) (P < .001). Among the predictive equations, the Mifflin-St Jeor method provided BMR estimates closest to the gold standard IC. When BMR measurement methods were compared to IC, 36.8% of measurements with the Harris-Benedict equation method, 50.4% with the Mifflin-St Jeor equation method, and 36.1% with the BIA method were within ± 10% agreement with IC measurements. Significant correlations were found between BMR and body composition parameters such as fat-free mass, muscle mass, and fat mass (R = 0.681, P < .001; R = 0.699, P < .001; R = 0.595, P < .001, respectively). Regression analysis identified that variables such as weight, height, body mass index, and muscle mass significantly predicted BMR measured by IC, accounting for 69.1% of the variance. This study underscores the challenges in assessing BMR in overweight and obese individuals. While IC remains the gold standard, predictive equations and BIA offer alternative methods. The Mifflin-St Jeor equation emerged as a practical option, closely aligning with IC results. However, discrepancies between methods and the influence of body composition highlight the importance of individualized approaches to BMR assessment in weight management strategies.

The metabolic cost of physical activity in mice using a physiology-based model of energy expenditure

ObjectivePhysical activity is a major component of total energy expenditure (TEE) that exhibits extreme variability in mice. Our objective was to construct a general, physiology-based model of TEE to accurately quantify the energy cost of physical activity. MethodsSpontaneous home cage physical activity, body temperature, TEE, and energy intake were measured with frequent sampling. The energy cost of activity was modeled considering six contributors to TEE (basal metabolic rate, thermic effect of food, body temperature, cold induced thermogenesis, physical activity, and body weight). An ambient temperature of 35 °C was required to remove the contribution from cold induced thermogenesis. Basal metabolic rate was adjusted for body temperature using a Q10 temperature coefficient. ResultsWe developed a TEE model that robustly explains 70–80% of the variance in TEE at 35 °C while fitting only two parameters, the basal metabolic rate and the mass-specific energy cost per unit of physical activity, which averaged 60 cal/km/g body weight. In Ucp1−/− mice the activity cost was elevated by 60%, indicating inefficiency and increased muscle thermogenesis. The diurnal rhythm in TEE was quantitatively explained by the combined diurnal differences in physical activity, body temperature, and energy intake. Incorporating body temperature into human basal metabolic rate measurements significantly reduced the inter-individual variation. ConclusionsThe physiology-based model of TEE allows quantifying the energy cost of physical activity. While applied here to mice, the model should be generally valid across species. Due to the effect of body temperature, we suggest that basal metabolic rate measurements be corrected to a reference body temperature, including in humans. Having an accurate cost of physical activity allows mechanistic dissection of disorders of energy homeostasis, including obesity.

Spatial variation in the evolutionary potential and constraints of basal metabolic rate and body mass in a wild bird.

An organism's energy budget is strongly related to resource consumption, performance, and fitness. Hence, understanding the evolution of key energetic traits, such as basal metabolic rate (BMR), in natural populations is central for understanding life-history evolution and ecological processes. Here we used quantitative genetic analyses to study evolutionary potential of BMR in two insular populations of the house sparrow (Passer domesticus). We obtained measurements of BMR and body mass (Mb ) from 911 house sparrows on the islands of Leka and Vega along the coast of Norway. These two populations were the source populations for translocations to create an additional third, admixed 'common garden' population in 2012. With the use of a novel genetic group animal model concomitant with a genetically determined pedigree, we differentiate genetic and environmental sources of variation, thereby providing insight into the effects of spatial population structure on evolutionary potential. We found that the evolutionary potential of BMR was similar in the two source populations, whereas the Vega population had a somewhat higher evolutionary potential of Mb than the Leka population. BMR was genetically correlated with Mb in both populations, and the conditional evolutionary potential of BMR (independent of body mass) was 41% (Leka) and 53% (Vega) lower than unconditional estimates. Overall, our results show that there is potential for BMR to evolve independently of Mb , but that selection on BMR and/or Mb may have different evolutionary consequences in different populations of the same species.

Differences in Adolescent’s Cardiometabolic Health: A Comparison Regarding Guided Team and Endurance Sports

Physical exercise can induce changes in gas exchange and ventilation kinetics. Of these, some will lead to various adaptations which can influence performance and health. We conducted a single-center observational study on 40 participants. Of them, 20 participants came from volleyball (Sample 1) and the other 20 participants came from triathlon (Sample 2). All participants underwent anthropometric and basal metabolic rate measurements, along with a laboratory aerobic capacity test (VO2peak). In Sample 1, the VO2peak was 2.38 L/min and 37.5 mL/min/kg, unlike in Sample 2, which had 2.31 L/min (p = 0.402, Mann-Whitney U = 204) and 43 mL/min/kg oxygen uptake (p = 0.0001). VE/VO2 was significantly different (p = 0.0002, Mann-Whitney U = 80), reaching 31.3 and 36.1 L/min in Sample 1 and Sample 2. Similar results were obtained regarding VE/VCO2 (p = 0.0074, Mann-Whitney U = 126), i.e., 31.3 and 33.9 L/min in Sample 1 and Sample 2. The contribution of physical activity was observed in both groups by taking into account the peak oxygen uptake. In comparison, the team sports sample showed an increased metabolic cost at the VO2peak.

Basal metabolic rate in free-ranging tropical birds lacks long-term repeatability and is influenced by ambient temperature.

Tropical birds live longer, have smaller clutches and invest more resources into self-maintenance than temperate species. These "slow" life-histories in tropical birds are accompanied by low basal metabolic rate (BMR). It has recently been suggested that the low BMR of tropical species may be related not to their slow "pace of life" or high ambient temperatures (Ta ) in tropical latitudes, but to the stability of environmental conditions in tropics. Since the repeatability of metabolic traits is higher in stable environments, such as laboratory conditions, we predicted that long-term repeatability of BMR in a tropical climate should be higher than in a temperate one. Contrary to our predictions, the repeatability of mass-independent BMR in 64 individuals of free-living tropical birds from Vietnam was low and insignificant after the species affiliation was taken into account. It indicates that BMR cannot be used as an individual long-term characteristic of tropical birds. On the other hand, tropical birds showed consistent differences in their mass-independent BMR at the interspecific level. Using BMR measurements from 1543 individuals of 134 species, we also found that different characteristics of Ta within the week preceding BMR measurements had a significant impact on the mass-independent BMR of tropical birds. The most significant effect was the difference between the absolute maximum and minimum Ta within a single week. Our results indicate that the physiology of tropical birds is more subject to changes than would be expected based on the notion of the stability of climatic conditions in the tropics.

Metabolic rates of aggressive and submissive phenotypes are colour blind in the polymorphic Gouldian finch.

Evidence from a number of species suggests that behaviours associated with social rank are positively correlated with metabolic rate. These studies, however, are based on metabolic measurements of isolated individuals, thereby ignoring potential effects of social interactions on metabolic rates. Here, we characterised three pertinent metabolic indices in the two predominant genetic colour morphs of the Gouldian finch (Erythrura gouldiae): diurnal resting metabolic rate (RMR), nocturnal basal metabolic rate (BMR) and exercise-induced maximal metabolic rate (MMR). Research reveals that red-headed morphs consistently dominate the less aggressive black-headed morphs and that the two morphs differ in other behavioural and physiological traits. We measured daytime RMR of intermorph naïve birds (first-year virgin males maintained in total isolation from opposite colour morphs) and their metabolic responses to viewing a socially unfamiliar bird of each colour. Subsequently, each bird was placed in a home cage with an opposite colour morph (intermorph exposed) and the series of measurements was repeated. Daytime RMR was indistinguishable between the two morphs, regardless of whether they were intermorph naïve or intermorph exposed. However, both red- and black-headed birds showed a greater short-term increase in metabolic rate when viewing an unfamiliar red-headed bird than when seeing a black-headed bird, but only when intermorph naïve. Measurements of BMR and exercise-induced MMR did not differ between the two morphs, and consequently, aerobic scope was indistinguishable between them. We propose that the behavioural differences between these two sympatric morphs are functionally complementary and represent evolutionary stable strategies permitting establishment of dominance status in the absence of metabolic costs.

496-P: Large-Scale Association of Basal Metabolic Rate and Blood Glucose Outcomes in People with Type 2 Diabetes

Background: Basal metabolic rate (BMR) measures the energy utilized by the body at rest. A growing body of literature reports increased BMR in people with type 2 diabetes (T2D), after controlling for sex, age and weight. We used blood glucose (BG) measurements and BMR values from the Apple Watch collected in the One Drop app, to measure the correlation of BMR and BG for the population as a whole, and for individuals over time. Method: Data included over 48,000 person-months of blood-glucose and BMR measurements from 5,585 people with T2D. BG was self-monitored except for 186 people who provided continuous glucose monitoring (CGM) data through Dexcom’s API. BMR values were summed daily and correlated with 30-day average BG for the study population by linear regression. For each person using CGM, we computed the Pearson correlation coefficient of BMR with Time-in-Range (TIR), and used a random effects model to compute the overall correlation and associated p-value. Results: The correlation coefficient of 30-day average BMR with 30-day average BG was 0.07 (p &amp;lt; 10-6), and of BMR with 30-day TIR was -0.26 (p &amp;lt; 10-6). The average correlation coefficient for individuals of BMR with TIR was -0.23±0.38. After applying the random effects model, the overall adjusted coefficient for individuals was -0.18 (p &amp;lt; 10-6). Conclusion: BMR and BG measurements collected in the One Drop app for 5,585 people with T2D show significant correlation of BMR with monthly BG levels at the population level and for individuals over time. This is among the largest scale analyses of such correlation, and the first one to use highly available BMR measurements from the Apple Watch. Disclosure Y. Wexler: None. D. Goldner: Employee; Self; One Drop.

Reassessing the definition of basal metabolic rate: Circadian considerations in avian studies

The importance of daily fluctuations in avian basal metabolic rate (BMR) was introduced in the classic paper by Aschoff and Pohl (1970) characterizing circadian differences. Since that time, there has been a shift in the BMR literature to accept only values measured in the ρ- (resting) phase of the day as true BMR. We argue that α- (active) and ρ-phases both represent BMR, analogous to the plasticity of BMR seen in seasonal variations, or associated with changes in body composition and restrictions in diet. Furthermore, we demonstrate that circadian differences in BMR are not even present in most polar birds and are sometimes absent in a variety of non-passerines. We argue for the ecological value of a 24 h BMR in order to compare with daily energy expenditure (field metabolic rate, FMR), which integrates entire days. We make recommendations for the reporting of BMR with sufficient information so readers will know time, season, etc. We also suggest that measures of BMR can be accepted during reproduction in birds, though with some caution.

GROWTH AND ENERGETICS OF ARCTIC TERN CHICKS (STERNA-PARADISAEA)

--We studied energy requirements of Arctic Tern chicks (Sterna paradisaea) in Ny ,idesund, Svalbard (79oN, 12oW) with special emphasis on thermoregulatory andactivity costs. We used doubly labeled water to estimate energy expenditure in the field (Ea•w) and made laboratory measurements ofthe different components of total energy requirement Comparison of DLW-estimates with oxygen consumption measurements howed that underestimated total energy expenditure 4.5-16.0% depending on the duration of the experiment. This was probably due to incorporation of isotopes in newly synthesized tissue. Field estimates of total energy expenditure from Ea• • were corrected accordingly. A tern chick model was used to measure operative temperature (T,). At midday T, reached values up to 20oC above ambient emperature (Ta) which ranged from 3.4-9.0oC. Based on the field estimates of Ea•w and Te and the laboratory measurements of basal metabolic rate and thermal conductance, we conclude that there was a considerable nergy saving (456 kJ = 26% of •eq) during the first 10-11 days of life, due to parental brooding. After this period, when the parents stop brooding, the energy required for thermoregulation accounted for only 16% of F_•q. From 10 days after hatching onwards, the energy needed for activity increased considerably, up to 50% of Er,q just before fledging (Day 20). Comparison of the energy budgets of Arctic Tern chicks with the more southerly occurring closely related Common Tern (S. hirundo; Ricklefs and White 1981) revealed only a slightly higher energy expenditure in the Arctic Tern chicks. Received 5 April 1988, accepted 23 November 1988. ENERGY expenditure of chicks living in arctic and antarctic environments has been considered to be dominated by the costs for thermoregulation. Many physiologists have focused on the ability of chicks to cope with low environmental temperatures (e.g. Maher 1964, Norton 1973, Aulie and Steen 1976, Boggs et al. 1977, Pedersen and Steen 1979, Bech et al. 1984, Jargensen and Blix 1985, Taylor 1985, Boersma 1986). However, the abiotic environment of chicks at high latitudes and the contribution of thermoregulatory costs to their total energy expenditure have not been quantified precisely. In addition to estimating thermoregulatory costs in relation to other energy requiring processes, interspecific comparison of closely related species from different latitudes should provide a better understanding of the influence of the polar environment on chick energy require-

Comparison of the Harris-Benedict Equation, Bioelectrical Impedance Analysis, and Indirect Calorimetry for Measurement of Basal Metabolic Rate among Adult Obese Filipino Patients with Prediabetes or Type 2 Diabetes Mellitus.

ObjectivesTo compare mean basal metabolic rate (BMR) estimated using Harris-Benedict equation (HB) and Bioelectrical Impedance Analysis (BIA) and the BMR measured using Indirect Calorimetry (IC) among adult obese Filipino patients with prediabetes or type 2 diabetes mellitus (T2DM).MethodologyThis was a multi-center, cross-sectional study based on review of outpatient medical records of adult, obese Filipino patients with pre-diabetes or type 2 diabetes mellitus who were seen prior to weight loss intervention at the Outpatient Clinic of St. Luke’s Medical Center-Quezon City and the Metabolic and Diabetes Center of Providence Hospital from August 2017 to January 2018. BMR was derived using three methods: Harris-Benedict equation, Bioelectrical Impedance Analysis and Indirect Calorimetry.ResultsA total of 153 subjects were included in the study. Eighty subjects (52%) have pre-diabetes while 73 subjects (48%) were diagnosed with T2DM. The mean BMR measured using IC is 1299±252 kcal/day while estimated mean BMR predicted using HB equation and BIA were 1628±251 kcal/day and 1635±260 kcal/day, respectively. Compared to measurement by IC, HBE and BIA significantly overestimated the mean BMR by 329 and 336 kcal/day, respectively (p-value=<0.0001). IC measured BMR showed strong positive correlation with weight and moderate positive correlation with height. Multiple stepwise regression analysis yielded the BMR prediction equation: BMR (kcal/day) = -780.806 + (11.108 x weight in kg) + (7.164 x height in cm).ConclusionAmong obese Filipinos with T2DM or prediabetes, HB equation and BIA tend to overestimate the BMR measured using IC.

Estimation of basal metabolic rate in Chinese: are the current prediction equations applicable?

BackgroundMeasurement of basal metabolic rate (BMR) is suggested as a tool to estimate energy requirements. Therefore, BMR prediction equations have been developed in multiple populations because indirect calorimetry is not always feasible. However, there is a paucity of data on BMR measured in overweight and obese adults living in Asia and equations developed for this group of interest. The aim of this study was to develop a new BMR prediction equation for Chinese adults applicable for a large BMI range and compare it with commonly used prediction equations.MethodsSubjects were 121 men and 111 women (age: 21–67 years, BMI: 16–41 kg/m2). Height, weight, and BMR were measured. Continuous open-circuit indirect calorimetry using a ventilated hood system for 30 min was used to measure BMR. A regression equation was derived using stepwise regression and accuracy was compared to 6 existing equations (Harris-Benedict, Henry, Liu, Yang, Owen and Mifflin). Additionally, the newly derived equation was cross-validated in a separate group of 70 Chinese subjects (26 men and 44 women, age: 21–69 years, BMI: 17–39 kg/m2).ResultsThe equation developed from our data was: BMR (kJ/d) = 52.6 x weight (kg) + 828 x gender + 1960 (women = 0, men = 1; R2 = 0.81). The accuracy rate (within 10 % accurate) was 78 % which compared well to Owen (70 %), Henry (67 %), Mifflin (67 %), Liu (58 %), Harris-Benedict (45 %) and Yang (37 %) for the whole range of BMI. For a BMI greater than 23, the Singapore equation reached an accuracy rate of 76 %. Cross-validation proved an accuracy rate of 80 %.ConclusionsTo date, the newly developed Singapore equation is the most accurate BMR prediction equation in Chinese and is applicable for use in a large BMI range including those overweight and obese.

Sources of Variation in the Basal Metabolic Rate of Laughing DovesSpilopelia senegalensis

Although avian basal metabolic rate (BMR) has been widely used in interspecific comparative studies, the sources of within-species variation in this parameter are still relatively poorly understood. Individually differing levels of activity and stress responsiveness have been proposed as potential sources for such variation in BMR. Here, I used an open flow-through respirometry system to examine the possible correlates of the time it takes individual Laughing Doves Spilopelia senegalensis to reach lowest oxygen consumption level in a metabolic chamber (‘BMR time’). Also, the association between individual response to handling stress and BMR was studied. Breath rate, measured while holding the bird in hand, was used as a measure of stress response to handling. It was found that ‘BMR time’ was not related to BMR or breath rate. However, its values were positively predicted by individuals' hematocrit. This indicates the potential importance of ‘BMR time’ as an indicator of activity. It was also found that breath rate was individually repeatable when two measurements were taken 12 hours apart. Breath rate was also positively related to BMR; however, the effect disappeared when mass-specific residuals of BMR were used. These results suggest that individual differences in response to standard handling stress probably do not affect BMR measurements.

Among- and within-individual correlations between basal and maximal metabolic rates in birds.

The aerobic capacity model proposes that endothermy is a by-product of selection favouring high maximal metabolic rates (MMR) and its mechanistic coupling with basal metabolic rate (BMR). Attempts to validate this model in birds are equivocal and restricted to phenotypic correlations (rP), thus failing to distinguish among- and within-individual correlations (rind and re). We examined 300 paired measurements of BMR and MMR from 60 house sparrows before and after two levels of experimental manipulation - testosterone implants and immune challenge. Overall, repeatability was significant in both BMR (R=0.25±0.06) and MMR (R=0.52±0.06). Only the testosterone treatment altered the rP between BMR and MMR, which resulted from contrasting effects on rind and re. While rind was high and significant (0.62±0.22) in sham-implanted birds, re was negative and marginally non-significant (-0.15±0.09) in testosterone-treated birds. Thus, the expected mechanistic link between BMR and MMR was apparent, but only in birds with low testosterone levels.

They live in the land down under: thyroid function and basal metabolic rate in the Blind Mole Rat, Spalax

The Israeli blind subterranean mole rat (Spalax ehrenbergi superspecies) lives in sealed underground burrows under extreme, hypoxic conditions. The four Israeli Spalax allospecies have adapted to different climates, the cool–humid (Spalax galili, 2 n = 52 chromosomes), semihumid (S. golani, 2 n = 54) north regions, warm–humid (S. carmeli, 2 n = 58) central region and the warm–dry S. judaei, 2 n = 60) southern regions. A dramatic interspecies decline in basal metabolic rate (BMR) from north to south, even after years of captivity, indicates a genetic basis for this BMR trait. We examined the possibility that the genetically-conditioned interspecies BMR difference was expressed via circulating thyroid hormone. An unexpected north to south increase in serum free thyroxine (FT4) and total 3, 5, 3′-triiodo-L-thyronine (T3) (p < 0.02) correlated negatively with previously published BMR measurements. The increases in serum FT4 and T3 were symmetrical, so that the T3:FT4 ratio – interpretable as an index of conversion of T4 to T3 in nonthyroidal tissues – did not support relative decrease in production of T3 as a contributor to BMR. Increased north-to-south serum FT4 and T3 levels also correlated negatively with hemoglobin/hematocrit. North-to-south adaptations in spalacids include decreased BMR and hematocrit/hemoglobin in the face of increasing thyroid hormone levels, arguing for independent control of hormone secretion and BMR/hematocrit/hemoglobin. But the significant inverse relationship between thyroid hormone levels and BMR/hematocrit/hemoglobin is also consistent with a degree of cellular resistance to thyroid hormone action that protects against hormone-induced increase in oxygen consumption in a hostile, hypoxic environment.

Basal metabolic rate and energy expenditure or rural farmers in Magubike village, Kilosa district, Tanzania

Measurement of basal metabolic rate (BMR) provides an important baseline for the determination of an individual’s total energy requirement. The study sought to establish human energy expenditure of rural farmers in Magubike village in Tanzania, through determination of BMR, physical activity level (PAL) and total energy expenditure (TEE). In addition, the study intended to provide an indication of the level of energy requirement for the rural people of Tanzania. The objective of the study was to determine energy expenditure of farmers in comparison to the mean caloric intake per capita and the WHO/FAO recommended energy requirements for developing countries. A cross-sectional study design involving 33 male and 31 female farmers was conducted on randomly selected households. Basal Metabolic rate and household activities were measured by indirect calorimetry, using the Douglas bag technique. Physical activity Level was measured by twenty-four hour activity diary and TEE calculated as a product of BMR and PAL. Men’s BMR was 4.7 MJ/day while that of women was 4.3 MJ/day. Farmers mean PAL was 2.20 ± 0.25 in men and 2.05 ± 0.23 in females and TEE was 10.24 MJ/day in men and 8.57 MJ/day in women. Both BMR and TEE were higher in men than in women. The measured energy expenditure for digging and weeding were 1.57 ± 0.3 kJ/min; 1.36 ± 0.31kJ/min in men and 1.58 ± 0.3 kJ/min; 1.49 ± 0.33 kJ/min in women. It was revealed that total energy expenditure of farmers in Magubike village was high with the values being above the mean daily calorie requirement per capita for Tanzania (8.15 MJ/day) but within the WHO/FAO recommended energy requirements (11.26 MJ/day) for developing countries. High energy expenditure was attributed to high energy levels spent in farm activities which were manual and labour intensive. This is likely to be the situation in many rural areas of Tanzania. More work on measurement of costs of farm activities and farmers work capacity are necessary to provide recommendations on energy needs of rural farmers.

Personality and basal metabolic rate in a wild bird population

Personality and metabolic rate are predicted to show covariance on methodological and functional grounds, but empirical studies at the individual level are rare, especially in natural populations. Here we assess the relationship between exploration behaviour, an important axis of personality, and basal metabolic rate (BMR) for 680 free‐living great tits Parus major, studied over three years. We find that exploration behaviour is weakly negatively related to BMR among female, but not male, birds. Moreover, we find exploration behaviour to be independent of methodological aspects of BMR measurements (e.g. activity levels, time to acclimatize) which have been suggested to be indicative of personality‐related activity or stress levels during measurement. This suggests that the weak link between exploration behaviour and BMR found here is functional rather than methodological. We therefore test the hypothesis that selection favours covariance between exploration behaviour and metabolic rate, but find no evidence for correlational survival or fecundity selection. Our data therefore provide at best only very weak evidence for a functional link between personality and metabolic rate, and we suggest that studies of personality and metabolic strategies, or personality and daily energy expenditure, are required to further resolve the link between personality and metabolic rate.

Quantitative genetics of basal metabolic rate and body mass in free‐living pied flycatchers

AbstractDespite basal metabolic rate (BMR) being one of the most commonly measured physiological traits and an important indicator of competitive ability, very little is known about its genetic basis and relation to other physiological traits. Here, we present the first attempt to estimate the multivariate basis of BMR using a natural population of pied flycatcher Ficedula hypoleuca breeding in the Tomsk Region, Western Siberia. We show relatively high and significant heritability of whole‐organism BMR, mass‐specific BMR and mass‐independent BMR (h 2 = 0.43, 0.55 and 0.52, respectively), which indicates the potential of these energetic traits to respond to direct selection. In contrast to some previous reports, we found that the genetic correlations between body mass and all three measures of BMR were not significantly different from zero. Independent evolution of body mass and BMR in this species should therefore be possible. Following a previous report, we also estimated the genetic correlations between the different BMR measures and show they are all close to unity, suggesting that they are, from a genetic point of view, a similar trait. Our results are in contrast with previous studies measuring the genetic basis of metabolic rates using aviary‐bred birds and highlight the importance of considering BMR in a natural setting.

Relationship Between Organ Masses and Basal Metabolic Rate (BMR) in Tree Sparrows (Passer montanus)

BMR (basal metabolic rate), body mass and organ masses of tree sparrows (Passer montanus) were measured to analyze the correlation between organ masses and BMR in tree sparrows, and to evaluate the underlying physiological causes of difference in BMR. Adult tree sparrows were live-trapped by mist net in Qiqihar City, Heilongjiang Province (47°29′N, 124°02′E). The closed circuit respirometer was used to measure the metabolic rate (MR), and controlled the ambient temperature by using a water bath (±0.5°C). Body masses were measured to the nearest 0.01 g before and after BMR measurements with a Sartorius balance (model BT25S). The mean value was recorded as body mass. Wet and dry masses of several organs were measured, too. BMR was (4.276± 0.385) mL O2/(g · h) and mean body mass was (18.522±0.110) g. Since not all the variables were normal distributed, a log10-transformation of those variables was employed to linearize them, prior to analyses. Simple regression analyses indicated that most organ masses showed a significant high correlation with body mass. Both the small intestine and rectum masses were notable exception to that trend. The body-mass-adjusted residual analysis showed that only the kidney wet mass, brain mass, stomach mass, small mass and rectum wet mass correlated with BMR. In addition, correlations between several organ masses and BMR were observed. Because of the inter-correlations of organ masses, a principal component analysis (PCA) was performed to redefine the morphological variability. The first four components whose eigenvalues were greater than 1 could explain 75.2% variance of BMR. The first component, whose proportion reached 30.19%, was affected mainly by stomach mass, small intestine mass and rectum mass. Therefore, the results supported the hypothesis that BMR was controlled by some “expensive metabolic” organs.

Circumpolar adaptation, social change, and the development of autoimmune thyroid disorders among the Yakut (Sakha) of Siberia

Alterations in thyroid function appear to play a central role in adaptation to Arctic environments. Increased thyroid activity in indigenous circumpolar populations is associated with upregulated metabolism, including elevated basal metabolic rate (BMR); however, little is known about the possible health consequences of these climate-induced changes on thyroid function. The focus of the present study is to determine the prevalence of autoimmune thyroid disorders and their lifestyle and metabolic correlates among a sample of indigenous Yakut adults from northeastern Siberia. Anthropometric dimensions, health data, and plasma samples were collected among 281 adults (143 women, 138 men; ≥18 years old) from the rural community of Berdygestiakh (62°N, 127°E; pop. 4,900), Sakha Republic (Yakutia), Russia. BMR measurements were available for 96 women and 98 men. Free triiodothyronine (T(3) ), free thyroxine (T(4) ), thyroid stimulating hormone (TSH), and anti-thyroid peroxidase antibody (TPOAb) levels were determined using enzyme immunoassay. Twenty-two percent of women and 6% of men had clinically elevated (>30 IU/ml) TPOAb. TPOAb was positively correlated with TSH (P < 0.01), T(3) (P < 0.05), and T(4) (P < 0.05) in women and showed a positive trend with T(4) (P = 0.06) in men. Monthly household income was significantly positively correlated with TPOAb in men (P < 0.01) and showed a trend among women (P = 0.06). Although preliminary, these findings document higher than expected TPOAb levels among Yakut women and suggest possible consequences of increased thyroid activity associated with circumpolar adaptation and social change.