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The scaling of metabolic rates to body size is widely considered to be of great biological and ecological importance, and much attention has been devoted to determining its theoretical and empirical value. Most debate centers on whether the underlying power law describing metabolic rates is 2/3 (as predicted by scaling of surface area/volume relationships) or 3/4 (\"Kleiber's law\"). Although recent evidence suggests that empirically derived exponents vary among clades with radically different metabolic strategies, such as ectotherms and endotherms, models, such as the metabolic theory of ecology, depend on the assumption that there is at least a predominant, if not universal, metabolic scaling exponent. Most analyses claimed to support the predictions of general models, however, failed to control for phylogeny. We used phylogenetic generalized least-squares models to estimate allometric slopes for both basal metabolic rate (BMR) and field metabolic rate (FMR) in mammals. Metabolic rate scaling conformed to no single theoretical prediction, but varied significantly among phylogenetic lineages. In some lineages we found a 3/4 exponent, in others a 2/3 exponent, and in yet others exponents differed significantly from both theoretical values. Analysis of the phylogenetic signal in the data indicated that the assumptions of neither species-level analysis nor independent contrasts were met. Analyses that assumed no phylogenetic signal in the data (species-level analysis) or a strong phylogenetic signal (independent contrasts), therefore, returned estimates of allometric slopes that were erroneous in 30% and 50% of cases, respectively. Hence, quantitative estimation of the phylogenetic signal is essential for determining scaling exponents. The lack of evidence for a predominant scaling exponent in these analyses suggests that general models of metabolic scaling, and macro-ecological theories that depend on them, have little explanatory power.

Background and aims: The causes of relapses of ulcerative colitis (UC) are unknown. Dietary factors have been implicated in the pathogenesis of UC. The aim of this study was to determine which dietary factors are associated with an increased risk of relapse of UC. Methods: A prospective cohort study was performed with UC patients in remission, recruited from two district general hospitals, who were followed for one year to determine the effect of habitual diet on relapse. Relapse was defined using a validated disease activity index. Nutrient intake was assessed using a food frequency questionnaire and categorised into tertiles. Adjusted odds ratios for relapse were determined using multivariate logistic regression, controlling for non-dietary factors. Results: A total of 191 patients were recruited and 96% completed the study. Fifty two per cent of patients relapsed. Consumption of meat (odds ratio (OR) 3.2 (95% confidence intervals (CI) 1.3–7.8)), particularly red and processed meat (OR 5.19 (95% CI 2.1–12.9)), protein (OR 3.00 (95% CI 1.25–7.19)), and alcohol (OR 2.71 (95% CI 1.1–6.67)) in the top tertile of intake increased the likelihood of relapse compared with the bottom tertile of intake. High sulphur (OR 2.76 (95% CI 1.19–6.4)) or sulphate (OR 2.6 (95% CI 1.08–6.3)) intakes were also associated with relapse and may offer an explanation for the observed increased likelihood of relapse. Conclusions: Potentially modifiable dietary factors, such as a high meat or alcoholic beverage intake, have been identified that are associated with an increased likelihood of relapse for UC patients. Further studies are needed to determine if it is the sulphur compounds within these foods that mediates the likelihood of relapse and if reducing their intake would reduce relapse frequency.

We investigated interindividual variation and intra-individual phenotypic flexibility in basal metabolic rate (BMR), total evaporative water loss (TEWL), body temperature (Tb), the minimum dry heat transfer coefficient (h), and organ and muscle size of five species of larks geographically distributed along an aridity gradient. We exposed all species to constant environments of 15°C or 35°C, and examined to what extent interspecific differences in physiology can be attributed to acclimation. We tested the hypothesis that birds from deserts display larger intra-individual phenotypic flexibility and smaller inter-individual variation than species from mesic areas. Larks from arid areas had lower BMR, TEWL, and h, but did not have internal organ sizes different from birds from mesic habitats. BMR of 15°C-acclimated birds was 18.0%, 29.1%, 12.2%, 25.3%, and 4.7% higher than of 35°C-acclimated Hoopoe Larks, Dunn's Larks, Spike-heeled Larks, Skylarks, and Woodlarks, respectively. TEWL of 15°C-acclimated Hoopoe Larks exceeded values for 35°C-acclimated individuals by 23% but did not differ between 15°C- and 35°C-acclimated individuals in the other species. The dry heat transfer coefficient was increased in 15°C-acclimated individuals of Skylarks and Dunn's Larks, but not in the other species. Body temperature was on average 0.4°C ± 0.15°C (mean ± 1 SEM) lower in 15°C-acclimated individuals of all species. Increased food intake in 15°C-acclimated birds stimulated enlargement of intestine (26.9-38.6%), kidneys (9.8-24.4%), liver (16.5-27.2%), and stomach (22.0-31.6%). The pectoral muscle increased in 15°C-acclimated Spike-heeled Larks and Skylarks, remained unchanged in Hoopoe Larks, and decreased in 15°C-acclimated Woodlarks and Dunn's Larks. We conclude that the degree of intra-individual flexibility varied between physiological traits and among species, but that acclimation does not account for interspecific differences in BMR, TEWL, and h in larks. We found no general support for the hypothesis that species from desert environments display larger intra-individual phenotypic flexibility than those from mesic areas. The coefficient of variation of larks acclimated to their natural environment was smaller in species from arid areas than in species from mesic areas for mass-corrected BMR and surface-specific h, but not for mass-corrected TEWL. The high repeatabilities of BMR, TEWL, and h in several species indicated a within-individual consistency on which natural selection could operate.

Aging women experience hormonal changes, such as decreased estrogen and increased circulating androgen, due to natural or surgical menopause. These hormonal changes make postmenopausal women vulnerable to body composition changes, muscle loss, and abdominal obesity; with a sedentary lifestyle, these changes affect overall energy expenditure and basal metabolic rate. In addition, fat redistribution due to hormonal changes leads to changes in body shape. In particular, increased bone marrow-derived adipocytes due to estrogen loss contribute to increased visceral fat in postmenopausal women. Enhanced visceral fat lipolysis by adipose tissue lipoprotein lipase triggers the production of excessive free fatty acids, causing insulin resistance and metabolic diseases. Because genes involved in β-oxidation are downregulated by estradiol loss, excess free fatty acids produced by lipolysis of visceral fat cannot be used appropriately as an energy source through β-oxidation. Moreover, aged women show increased adipogenesis due to upregulated expression of genes related to fat accumulation. As a result, the catabolism of ATP production associated with β-oxidation decreases, and metabolism associated with lipid synthesis increases. This review describes the changes in energy metabolism and lipid metabolic abnormalities that are the background of weight gain in postmenopausal women.

Individual differences in the energy cost of self-maintenance (resting metabolic rate, RMR) are substantial and the focus of an emerging research area. These differences may influence fitness because self-maintenance is considered as a life-history component along with growth and reproduction. In this review, we ask why do some individuals have two to three times the ‘maintenance costs’ of conspecifics, and what are the fitness consequences? Using evidence from a range of species, we demonstrate that diverse factors, such as genotypes, maternal effects, early developmental conditions and personality differences contribute to variation in individual RMR. We review evidence that RMR is linked with fitness, showing correlations with traits such as growth and survival. However, these relationships are modulated by environmental conditions (e.g. food supply), suggesting that the fitness consequences of a given RMR may be context-dependent. Then, using empirical examples, we discuss broad-scale reasons why variation in RMR might persist in natural populations, including the role of both spatial and temporal variation in selection pressures and trans-generational effects. To conclude, we discuss experimental approaches that will enable more rigorous examination of the causes and consequences of individual variation in this key physiological trait.

A key endeavor in evolutionary physiology is to identify sources of among- and within-individual variation in resting metabolic rate (RMR). Although males and females often differ in whole-organism RMR due to sexual size dimorphism, sex differences in RMR sometimes persist after conditioning on body mass, suggesting phenotypic differences between males and females in energy-expensive activities contributing to RMR. One potential difference is locomotor activity, yet its relationship with RMR is unclear and different energy budget models predict different associations. We quantified locomotor activity (walking) over 24 h and RMR (overnight) in 232 male and 245 female Drosophila melanogaster that were either mated or maintained as virgins between two sets of measurements. Accounting for body mass, sex, and reproductive status, RMR and activity were significantly and moderately repeatable (RMR: 𝑅 = 0.33 ± 0.06; activity: 𝑅 = 0.58 ± 0.03). RMR and activity were positively correlated among (𝑟ind = 0.26 ± 0.09) but not within (𝑟e = 0.05 ± 0.06) individuals. Moreover, activity varied throughout the day and between the sexes. Partitioning our analysis by sex and activity by time of day revealed that all among-individual correlations were positive and significant in males but nonsignificant or even significantly negative in females. Such differences in the RMR-activity covariance suggest fundamental differences in how the sexes manage their energy budget.

Facultative hyperthermia, the elevation of body temperature above normothermic levels, during heat exposure, importantly affects the water economy and heat balance of terrestrial endotherms. We currently lack a mechanistic understanding of the benefits hyperthermia provides for avian taxa. Facultative hyperthermia has been proposed to minimize rates of water loss via three distinct mechanisms: M1) by maintaining body temperature (Tb) above environmental temperatures (Te), heat can be lost non‐evaporatively, saving water; M2) by minimizing the thermal gradient when Te > Tb, environmental heat gain and evaporative water loss rates are reduced; and M3) by storing heat via increases in Tb which reduces evaporative heat loss demands and conserves water. Although individuals may benefit from all three mechanisms during heat exposure, the relative importance of each mechanism has not been quantified among species that differ in their body size, heat tolerance and mechanisms of evaporative heat dissipation. We measured resting metabolism, evaporative water loss and real‐time Tb from 33 species of birds representing nine orders ranging in mass from 8 to 300 g and estimated the water savings associated with each proposed mechanism. We show that facultative hyperthermia varies in its benefits among species. Small songbirds with comparatively low evaporative cooling capacities benefit most from (M1), and hyperthermia maintains a thermal gradient that allows non‐evaporative heat losses. Other species benefited most from (M2) minimizing evaporative losses via a reduced thermal gradient for heat gain at high Te. We found that (M3), heat storage, only improved the water economy of the sandgrouse, providing little benefit to other species. We propose that differences in the frequency and magnitude of hyperthermia will drive taxon‐specific differences in temperature sensitivity of tissues and enzymes and that the evolution of thermoregulatory mechanisms of evaporative heat dissipation may contribute to differences in basal metabolic rate among avian orders. Understanding the mechanistic basis of heat tolerance is essential to advance our understanding of the ecology of birds living in hot environments that are warming rapidly, where extreme heat events are already re‐structuring avian communities. A plain language summary is available for this article. Plain Language Summary

This paper contains a revision of the Harris–Benedict equations through the development and validation of new equations for the estimation of resting metabolic rate (RMR) in normal, overweight, and obese adult subjects, taking into account the same anthropometric parameters. A total of 722 adult Caucasian subjects were enrolled in this analysis. After taking a detailed medical history, the study enrolled non-hospitalized subjects with medically and nutritionally controlled diseases such as diabetes mellitus, cardiovascular disease, and thyroid disease, excluding subjects with active infections and pregnant or lactating women. Measurement of somatometric characteristics and indirect calorimetry were performed. The values obtained from RMR measurement were compared with the values of the new equations and the Harris–Benedict, Mifflin–St Jeor, FAO/WHO/UNU, and Owen equations. New predictive RMR equations were developed using age, body weight, height, and sex parameters. RMR males: (9.65 × weight in kg) + (573 × height in m) − (5.08 × age in years) + 260; RMR females: (7.38 × weight in kg) + (607 × height in m) − (2.31 × age in years) + 43; RMR males: (4.38 × weight in pounds) + (14.55 × height in inches) − (5.08 × age in years) + 260; RMR females: (3.35 × weight in pounds) + (15.42 × height in inches) − (2.31 × age in years) + 43. The accuracy of the new equations was tested in the test group in both groups, in accordance with the resting metabolic rate measurements. The new equations showed more accurate results than the other equations, with the equation for men (R-squared: 0.95) showing better prediction than the equation for women (R-squared: 0.86). The new equations showed good accuracy at both group and individual levels, and better reliability compared to other equations using the same anthropometric variables as predictors of RMR. The new equations were created under modern obesogenic conditions, and do not exclude individuals with regulated (dietary or pharmacological) Westernized diseases (e.g., cardiovascular disease, diabetes, and thyroid disease).

The present study assessed whether total daily energy expenditure measured via doubly labeled water (TDEEDLW) could be accurately estimated via 24-hour physical activity recall (24hPAR) and whether different MET estimates impacted TDEE. The participants comprised a convenience sample of 40 adults (21 women and 19 men) from an urban tropical setting. Laboratory staff took anthropometric measurements, assessed basal metabolic rate via indirect calorimetry, took a baseline urine sample, and administered a DLW dose. Over the following 14 days, participants collected daily urine samples and answered four 24hPARs. The agreement between the measured and estimated methods was investigated. Means (SD) were: 30.4 (11.0) years for age; 23.1 (2.7) kg/m2 for BMI; and 1.75 (0.26) for physical activity level (TDEEDLW/basal metabolic rate). Data from 24hPARs allowed estimation of TDEE using metabolic equivalent (MET) codes from the Compendium of Physical Activities with its traditional resting MET value or by estimating resting values via sex-specific equations derived from a probability sample of Niteroian adults (METN). Mean TDEEDLW was 2350.8 (527.9) kcal/d and was significantly overestimated by 24hPAR TDEE, when using the traditional MET value, at 2699.7 (537.6) kcal/d (+17.7%, P = 0.0001), and by +26.7% (P < 0.0001) for women only. In contrast, mean 24hPAR TDEE, when using the METN values, did not differ significantly for the entire group (-0.2%, P = 0.9333), neither for women (+5.5%, P = 0.1867), nor for men (–5.6%, P = 0.1516). Among urban Brazilians, TDEE using sex-specific MET values from relevant population-specific equations can be feasibly and accurately estimated via 24hPAR, and, for men only, when using the conventional MET. •Total daily energy expenditure was measured by doubly labeled water in a sample of urban Brazilian adults.•24-hour physical activity recall can accurately estimate total daily energy expenditure.•Using the traditional MET value overestimates total daily energy expenditure in women, which makes scientists impart bias into their results.•Using sex-specific MET values accurately estimates total daily energy expenditure.

•Curcumin ameliorates inflammation and improves insulin sensitivity in high-fat-diet–induced obese mice.•Curcumin improves energy expenditure in high-fat-diet–fed mice, when accompanied by the enhancement of metabolic activity in brown and white fat.•The beneficial effect of curcumin on energy metabolism may be mediated by activation of FNDC5/irisin. Curcumin (Cur) has a beneficial role in preventing metabolic dysfunctions; however, the underlying mechanism are not yet fully understood. The aim of this study was to evaluate whether the beneficial metabolic effects of curcumin are associated with the regulation of energy metabolism and activation of fibronectin type 3 domain-containing protein 5 (FNDC5)/irisin. We used cellular and molecular techniques to investigate the effects of Cur on C57 BL/6 mice that were fed either a control diet or a high-fat diet (HFD) with or without 0.2% Cur for 10 wk. Factors involved in energy metabolism, inflammatory responses, and insulin signaling, as well as the involvement of FNDC5/irisin pathway, were assessed. Cur alleviated adiposity and suppressed inflammatory response in white adipose tissue (WAT) of HFD mice. Meanwhile, Cur administration increased plasma irisin concentration and improved insulin sensitivity of HFD mice. Cur increased the oxygen consumption and heat production and reduced respiratory exchange ratio (RES) in HFD mice, which were accompanied by the enhancement of metabolic activity in brown fat and inguinal WAT. Additionally, the improvement of basal metabolic rate by Cur may be partly regulated by the FNDC5/ p38 mitogen-activated protein kinase (p38 MAPK)/extracellular signal-related kinase (ERK) 1/2 pathway. These findings demonstrated that dietary Cur alleviated diet-induced adiposity by improving insulin sensitivity and whole body energy metabolism via the FNDC5/p38 MAPK/ERK pathways.