Increase In Resting Metabolic Rate Research Articles

1634-P: Brown Adipose Tissue and Muscle Responses to Tolerable Cold in Black and White Young Lean Men

There has been a renewed interest in brown adipose tissue (BAT) as a therapeutic target for diabetes and obesity treatments due to its ability to consume glucose and expend energy in response to cold temperatures and Beta-adrenergic stimulation. However, comparisons of BAT in different races are limited. To address this knowledge gap, we directly compared healthy, young, lean Black and White men in a controlled inpatient study using a whole-room indirect calorimeter. 12 Black and 12 White men completed a 6-13-day protocol with randomized calorimeter temperatures between 18-31°C for 5 hours. Resting metabolic rate (RMR) was measured under reclined, fasted conditions with standard clothing. Body composition was measured by dual x-ray absorptiometry and BAT and muscle glucose uptake activity was quantified using 18-F Fluorodeoxyglucose (18-F FDG) PET-CT following the last chamber study where each individual's coldest tolerable temperature (Tct) was used. Basal metabolic rate (BMR) was defined as minimum RMR and the cold-induced thermogenesis (CIT) was calculated as the percentage increase of RMR above BMR in the cold. The groups were similar in age (23.8±4.7 yrs) and BMI (23.1±1.5 kg/m2) and their Tct (21.0±1.4°C; p=0.54) and CIT (12.1±8.1 kcal/h; p=0.8) were not different. While White males had significantly higher BAT volume (334 ± 188mL vs 242 ± 89mL; p=0.045), BAT volume was comparable between the groups after normalizing to body volume. BAT activity was similar between the groups. Among all muscle activity measured, the intercostal muscles in the Black males had significantly higher activity (p=0.002) and activity was present in all 12 Black participants but only 4 of 12 White males. Individual BAT or muscle activity did not correlate with each other nor with Tct or CIT. Our data suggest that the cold-induced BAT activity was comparable in Black and White young, lean men. The surprising difference in intercostal muscle activity warrants further investigation. Disclosure R.J.Thomas: None. R.Brychta: None. A.B.Courville: None. S.Mcgehee: None. A.M.Cypess: None. K.Y.Chen: None.

Heat tolerance limits of Mediterranean songbirds and their current and future vulnerabilities to temperature extremes.

Songbirds are one of the groups most vulnerable to extreme heat events. Although several recent studies have assessed their physiological responses to heat, most of them have focused solely on arid-zone species. We investigated thermoregulatory responses to heat in eight small-sized songbirds occurring in the Mediterranean Basin, where heatwaves are becoming more frequent and intense. Specifically, we determined their heat tolerance limits (HTLs) and evaporative cooling efficiency, and evaluated their current and future vulnerabilities to heat in southwestern Iberia, a Mediterranean climate warming hotspot. To do this, we exposed birds to an increasing profile of air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), evaporative cooling efficiency (the ratio between evaporative heat loss and metabolic heat production) and body temperature (Tb). HTL ranged between 40 and 46°C across species, and all species showed rapid increases in RMR, EWL and Tb in response to increasing Ta. However, only the crested lark (Galerida cristata) achieved an evaporative cooling efficiency greater than 1. The studied songbirds currently experience summer Ta maxima that surpass the upper critical temperatures of their thermoneutral zone and even their HTL. Our estimates indicate that five of the eight species will experience moderate risk of lethal dehydration by the end of the century. We argue that the limited heat tolerance and evaporative cooling efficiency of small-sized Mediterranean songbirds make them particularly vulnerable to heatwaves, which will be exacerbated under future climate change scenarios.

Acute Effects of Whole-Body Vibration on Resting Metabolic Rate and Substrate Utilisation in Healthy Women.

Simple SummaryWhole-body vibration induces a number of physiological responses and is used both in physical training, and in the treatment of patients with various diseases. Whole-body vibration increases blood flow, skin temperature, bone density, muscle strength and affects the functions of the nervous system. The effect of whole-body vibration on metabolism is interesting. It has been suggested that whole-body vibration shifts energy metabolism towards carbohydrate utilisation and that this may increase post-exercise oxygen uptake. Increased resting metabolism (increased energy expenditure) during whole-body vibration may indicate that whole-body vibration can be used as an adjunct to treatment programs for overweight or metabolic disorders.The aim of the study was to determine the acute effects of single-whole-body vibration (WBV) on resting metabolic rate (RMR) and carbohydrate–lipid profile of blood in young, healthy women. The participants, in a randomised controlled crossover study, participated in two trials: WBV and a vibration simulation (placebo). The WBV was performed in the prone position and cycloidal-oscillatory vibration was used. The RMR measurement (calorimetry) was performed: before the WBV, during WBV, immediately after the completion of WBV, and 1 h after the completion of WBV. For biochemical analyses, venous blood was collected. During WBV, there was a significant increase in RMR compared to baseline. Immediately after and 1 h following the end of the WBV, RMR was close to baseline levels (p > 0.05). The increased energy expenditure resulted from the increased utilisation of carbohydrates and proteins during the vibration. In the placebo condition, there were no significant changes over time in the level of the studied indices during calorimetry. The WBV had no significant effects on the level of glucose in the blood. The applied vibration did not significantly affect the concentration of the analysed lipid indices, which were within the physiological norms for all measurements. Results indicate the need for further research to establish the physiological mechanisms underlying the observed effects of WBV on resting metabolic rate.

Relationship between Seasonal Changes in Food Intake and Energy Metabolism, Physical Activity, and Body Composition in Young Japanese Women.

We investigated seasonal changes in food intake, energy metabolism, and physical activity (PA) and explored their associations with body composition. In total, 28 women aged 20–23 years in the Kansai area of Japan participated in this year-long study spanning the winter, spring, and summer seasons. A dietary investigation was performed using the weight recording method, and the amount of histidine in the diet, which may be related to the regulation of energy intake, was calculated. Resting metabolic rate (RMR), body composition, and PA were measured using indirect calorimetry, bioelectrical impedance analysis, and uniaxial accelerometry, respectively. The results showed that energy intake was highest in winter, decreased significantly with increasing temperature, and decreased by 25% in summer. As the intake of histidine in the diet did not increase in summer, it did not seem to be involved in the suppression of energy intake. RMR was highest in winter and decreased significantly in summer by 20%. The amount of PA was low in winter, increased significantly in the spring, and decreased again in summer. Body weight increased in winter, with an accumulation of fat in the trunk and arms, and decreased in summer, with a reduction in the amount of fat. Greater energy intake and less PA in winter induced an increment in body weight despite the increase in RMR. There were no significant changes in lean body mass between the seasons; however, the muscle weight of the lower limbs increased significantly in spring and in summer compared with that in winter (p < 0.001). Thus, seasonal changes in food intake, energy metabolism, and PA occur, with resultant changes in the body composition under comfortable air-conditioned environments.

Comparison of Indirect Calorimetry and Common Prediction Equations for Evaluating Changes in Resting Metabolic Rate Induced by Resistance Training and a Hypercaloric Diet.

Rodriguez, C, Harty, PS, Stratton, MT, Siedler, MR, Smith, RW, Johnson, BA, Dellinger, JR, Williams, AD, White, SJ, Benavides, ML, and Tinsley, GM. Comparison of indirect calorimetry and common prediction equations for evaluating changes in resting metabolic rate induced by resistance training and a hypercaloric diet. J Strength Cond Res 36(11): 3093-3104, 2022-The ability to accurately identify resting metabolic rate (RMR) changes over time allows practitioners to prescribe appropriate adjustments to nutritional intake. However, there is a lack of data concerning the longitudinal utility of commonly used RMR prediction equations. The purpose of this study was to evaluate the validity of several commonly used prediction equations to track RMR changes during a hypercaloric nutritional intervention and supervised resistance exercise training program. Twenty resistance-trained men completed the study. The protocol lasted 6 weeks, and subjects underwent RMR assessments by indirect calorimetry (IC) preintervention and postintervention to obtain reference values. Existing RMR prediction equations based on body mass (BM) or dual-energy X-ray absorptiometry fat-free mass (FFM) were also evaluated. Equivalence testing was used to evaluate whether each prediction equation demonstrated equivalence with IC. Null hypothesis significance testing was also performed, and Bland-Altman analysis was used alongside linear regression to assess the degree of proportional bias. Body mass and FFM increased by 3.6 ± 1.7 kg and 2.4 ± 1.6 kg, respectively. Indirect calorimetry RMR increased by 165 ± 97 kcal·d -1 , and RMR:FFM increased by 5.6 ± 5.2%. All prediction equations underestimated mean RMR changes relative to IC, with magnitudes ranging from 75 to 155 kcal·d -1 , while also displaying unacceptable levels of negative proportional bias. In addition, no equation demonstrated equivalence with IC. Common RMR prediction equations based on BM or FFM did not fully detect the increase in RMR observed with resistance training plus a hypercaloric diet. Overall, the evaluated prediction equations are unsuitable for estimating RMR changes in the context of this study.

Daily intake of yogurt drink fortified either with vitamin D alone or in combination with added calcium causes a thyroid-independent increase of resting metabolic rate in adults with type 2 diabetes: a randomized, double-blind, clinical trial.

We investigated the effect of daily intake of yogurt drink fortified with either vitamin D alone or with added calcium on resting metabolic rate (RMR), thyroid hormones and homeostatic model assessment for insulin resistance in subjects with type 2 diabetes (T2D). A total of 75 adult subjects with T2D were randomly assigned to 1 of the 3 groups to receive either D-fortified yogurt drink (DY; 1000IU vitaminD/day), Ca-D-fortified yogurt drink (CDY; 1000IU vitamin D plus 500mg calcium), or plain yogurt drink for 12 weeks. All assessments were done at the baseline and after the intervention. The concentrations of anti-thyroid peroxidase antibody (anti-TPO-Ab), intact parathyroid hormone (iPTH) and thyroid stimulating hormone (TSH) had declined significantly compared with baseline values only in the CDY group. The mean RMR increased in both DY and CDY groups (p< 0.001 for both). Also, changes of serum concentrations of 25-hydroxycalciferol (B= 2.96, 95% confidence interval (CI)= 1.3 to 4.6, p= 0.001) and iPTH (B= -2.41, 95%CI= -4.5 to -0.31, p= 0.025) remained significant predictors of RMR changes even after adjustment for changes of serum concentrations of TSH (B= -18.2, 95% CI= -61.7 to 25.2, p= 0.406). Daily intake of vitamin D together with calcium at physiological doses has attenuating effect on anti-TPO-Ab and TSH. Also, vitamin D with or without added calcium causes a significant thyroid-independent increase in RMR in euthyroid subjects with T2D. Registered at clinicaltrials.gov as NCT01229891. Novelty: Daily intake of vitamin D with calcium at physiological doses has attenuating effect on anti-TPO-Ab and TSH. Vitamin D with or without added calcium causes a thyroid-independent increase in RMR in euthyroid subjects with T2D.

Performance and Health Decrements Associated With Relative Energy Deficiency in Sport for Division I Women Athletes During a Collegiate Cross-Country Season: A Case Series.

The purpose of this case series was to evaluate the presence of low Energy Availability (EA) and its impact on components of Relative Energy Deficiency in Sport (RED-S) in a population of female collegiate runners. Seven female NCAA Division I athletes (age: 22.3 ± 1.5 yrs; height: 169.7 ± 5.7 cm; weight: 58.3 ± 4.1 kg) were tracked from August until February, covering the beginning (Pre XC), end (Post XC) of their competitive cross country season, and beginning of the following track season (Pre Track). The athletes were assessed for female athlete triad (Triad) risk, energy availability, body composition, resting metabolic rate (RMR), nutritional intake, and blood markers (including vitamin D, ferritin, and triiodothyronine (T3)). From Pre XC to Post XC there were no significant differences in body mass, fat free mass or body fat percentage. At Pre XC, mean EA was 31.6 ± 13.3 kcal/kg FFM∙d-1. From Post XC to Pre Track, there was a significant increase in body mass (59.1 ± 5.1 to 60.6 ± 5.7 kg, p<0.001,d=0.27). From Post XC to Pre Track, there was a significant increase in RMR (1466 ± 123.6 to 1614.6 ± 89.1 kcal·d-1, p<0.001,d=2.6). For 25(OH) vitamin D, there was a significant reduction from Pre XC to Post XC (44.1 ± 10.6 vs 39.5 ± 12.2 ng·mL-1, p=0.047,d=-0.4), and a significant increase from Post XC to Pre Track (39.5 ± 12.2 vs. 48.1 ± 10.4 ng·mL-1, p=0.014,d=0.75). For ferritin, there was a trend towards a decrease from Pre XC to Post XC (24.2 ± 13.2 vs. 15.7 ± 8.8 ng·mL-1, p=0.07, d=-0.75), as well as a trend toward an increase from Post XC to Pre Track (15.7 ± 8.8 vs. 34.1 ± 18.0 ng·mL-1, p=0.08, d=1.3). No differences in T3 were observed across time points. Average Triad risk score was 2.3 ± 1.4. Notably, 5 of 7 athletes met criteria for moderate risk. Despite many athletes meeting criteria for low EA and having elevated Triad risk assessment scores, most were able to maintain body mass and RMR. One athlete suffered severe performance decline and a reduced RMR. Surprisingly, she was the only athlete above the recommended value for ferritin. Following increased nutritional intake and reduced training volume, her performance and RMR recovered. Changes in body mass and body composition were not indicative of the presence of other concerns associated with RED-S. This exploratory work serves as a guide for future, larger studies for tracking athletes, using RMR and nutritional biomarkers to assess RED-S.

Decreased Capacity for Thermogenesis During Aging in Lean and Obese LA/Ntul//‐ cp (corpulent) Rats

Obesity develops in the obese phenotype of the LA/Ntul//-cp (corpulent) rat strain by 6 weeks of age. Groups [n=12-20 rats/phenotype] of congenic female lean and obese LA/Ntul//-cp (corpulent) rats were fed ad libitum standardized Purina #5012 diet for 4, 14, or 24 months of age. Measures of Body weight (BW) and of resting metabolic rate (RMR) at thermal neutrality, and for up to 45 minutes of 4°C spontaneous cold exposure, and norepinephrine-stimulated (NE) thermogenesis (100 µg sc) were determined at each age. BW of lean rats increased only gradually during the study (p=N.S.), but BW of obese phenotype were 2-fold greater at 4 months (p=0.05) and increased progressively to 4-fold greater than lean littermates by 24 months of age (p=<0.01). RMR in the lean phenotype decreased gradually at each age (p=<0.05) and was greater in the lean than the obese phenotype at all ages studied (p=<0.05). Cold exposure resulted in a dramatic 5-fold increase in the VO2 after 5 minutes in 4-month-old rats, which increase in thermogenesis was less dramatic at each successive age. In 24-month-old lean rats however, the cold induced increases in RMR were markedly diminished to only ~3x RMR at 5 minutes cold exposure but remained similar to the other lean age groups thereafter. In the obese phenotype, the peak responses at 5 minutes were significantly lower than those of lean rats at 5 minutes in 4- and 14-month-old rats and were also markedly impaired in 24-month-old obese rats. NE resulted in a 1.5-fold increase in VO2 in the lean phenotype at all ages studied, while in obese rats NE resulted in a ~1.4-fold increase in VO2 at 4 months with non-significant 1.2-fold increases at the two older ages. In both phenotypes, the RMR and the NE-stimulated VO2 responses tended to decrease with increasing age. The results of this study demonstrate that the body weights of the obese phenotype are significantly greater than their lean littermates throughout the age spectrum studied from 6 weeks of age, and that both resting RMR, cold, and NE-stimulated thermogenesis are decreased in the obese compared to the lean phenotype, become further decreased with advancing age, and may be a contributing factor in the efficiency of energy conservation and expenditure in the obese phenotype of this animal strain.

88116 Effect of conjugated estrogens and bazedoxifene on glucose, energy and lipid metabolism in obese postmenopausal women

ABSTRACT IMPACT: A short treatment of 8 obese postmenopausal women with conjugated estrogens and bazedoxifene does not alter insulin sensitivity or ectopic fat but increases serum markers of hepatic de novo lipogenesis and production of triacylglycerides. OBJECTIVES/GOALS: Combining conjugated estrogens (CE) with the selective estrogen receptor modulator bazedoxifene (BZA) is a novel, orally-administered menopausal therapy. We investigated the effect of CE/BZA on insulin sensitivity, energy metabolism, and serum metabolome in postmenopausal women with obesity. METHODS/STUDY POPULATION: We conducted a randomized, double-blind, crossover pilot trial, testing the effect of CE/BZA on cardiometabolic health in postmenopausal women. Eight postmenopausal women (age 50-60 y, BMI 30-40 kg/m2) were randomization to an 8-week CE/BZA or placebo treatment separated by an 8-week washout period [NCT02274571]. The primary outcome was insulin sensitivity (hyperinsulinemic-euglycemic clamp), while secondary outcomes included body composition (DXA); resting metabolic rate (RMR); substrate oxidation (indirect calorimetry); ectopic lipids (1H-MRS); fat cell size, adipose and skeletal muscle gene expression (biopsies); inflammatory markers; and serum metabolome (LC/MS). RESULTS/ANTICIPATED RESULTS: CE/BZA had no effect on insulin sensitivity, body composition, ectopic fat, or substrate oxidation, but resulted in a non-significant increase in RMR (basal: p=0.06; high-dose clamp: p=0.08) compared to placebo. CE/BZA increased serum high-density lipoprotein cholesterol. CE/BZA also increased serum diacylglycerol (DAG) and triacylglycerol (TAG) species containing long-chain saturated, mono- and polyunsaturated fatty acids (FAs), and decreased long-chain acylcarnitines. These findings possibly reflect increased hepatic de novo FA synthesis and esterification into TAGs, and decreased FA oxidation, respectively (p&lt;0.05). CE/BZA increased serum phosphatidylcholines, phosphatidylethanolamines, ceramides, and sphingomyelins, possibly reflecting the increase in lipoproteins (p&lt;0.05). DISCUSSION/SIGNIFICANCE OF FINDINGS: A short treatment of postmenopausal women with CE/BZA did not alter insulin action or ectopic fat, but increased markers of hepatic de novo lipogenesis and TAG production. Study limitations include a small sample size and short treatment period. A larger, fully powered study is needed to validate the potential metabolic benefit of combining CE with BZA.

Effect of Acute and Chronic Dietary Supplementation with Green Tea Catechins on Resting Metabolic Rate, Energy Expenditure and Respiratory Quotient: A Systematic Review

The consumption of green tea catechins (GTC) is associated with modulations of fat metabolism and consequent weight loss. The aim of this systematic review was to investigate the effect of GTC on resting metabolic rate (RMR), energy expenditure (EE), and respiratory quotient (RQ). Eligible studies considered both the chronic and acute intake of GTC-based supplements, with epigallocatechin gallate (EGCG) doses ranging between 100–800 mg. Findings from 15 studies (n = 499 participants) lasting 8–12 weeks (for chronic consumption) or 1–3 days (for acute intake) are summarized. This review reveals the positive effects of GTC supplementation on RQ values (272 subjects). Regarding the effects of acute and chronic GTC supplementation on RMR (244 subjects) and EE (255 subjects), the results did not allow for a definitive conclusion, even though they were promising, because some reported a positive improvement (two studies revealed an increase in RMR: one demonstrated an RMR increase of 43.82 kcal/day and another demonstrated an increase of 260.8 kcal/day, mainly when subjects were also engaged in resistance training exercise). Considering GTC daily dose supplementation, studies in which modifications of energetic parameters occurred, in particular RQ reduction, considered GTC low doses (100–300 mg). GTC may be useful for improving metabolic profiles. Further investigations are needed to better define adequate doses of supplementation.

Effect of conjugated estrogens and bazedoxifene on glucose, energy and lipid metabolism in obese postmenopausal women.

Combining conjugated estrogens (CE) with the selective estrogen receptor modulator bazedoxifene (BZA) is a novel, orally administered menopausal therapy. We investigated the effect of CE/BZA on insulin sensitivity, energy metabolism, and serum metabolome in postmenopausal women with obesity. Randomized, double-blind, crossover pilot trial with washout was conducted at Pennington Biomedical Research Center. Eight postmenopausal women (age 50-60 years, BMI 30-40 kg/m2) were randomized to 8 weeks CE/BZA or placebo. Primary outcome was insulin sensitivity (hyperinsulinemic-euglycemic clamp). Secondary outcomes included body composition (DXA); resting metabolic rate (RMR); substrate oxidation (indirect calorimetry); ectopic lipids (1H-MRS); fat cell size, adipose and skeletal muscle gene expression (biopsies); serum inflammatory markers; and serum metabolome (LC/MS). CE/BZA treatment produced no detectable effect on insulin sensitivity, body composition, ectopic fat, fat cell size, or substrate oxidation, but resulted in a non-significant increase in RMR (basal: P = 0.06; high-dose clamp: P = 0.08) compared to placebo. CE/BZA increased serum high-density lipoprotein (HDL)-cholesterol. CE/BZA also increased serum diacylglycerol (DAG) and triacylglycerol (TAG) species containing long-chain saturated, mono- and polyunsaturated fatty acids (FAs) and decreased long-chain acylcarnitines, possibly reflecting increased hepatic de novo FA synthesis and esterification into TAGs for export into very low-density lipoproteins, as well as decreased FA oxidation, respectively (P < 0.05). CE/BZA increased serum phosphatidylcholines, phosphatidylethanolamines, ceramides, and sphingomyelins, possibly reflecting the increase in serum lipoproteins (P < 0.05). A short treatment of obese postmenopausal women with CE/BZA does not alter insulin action or ectopic fat but increases serum markers of hepatic de novo lipogenesis and TAG production.

Nutrient pattern of unsaturated fatty acids and vitamin E increase resting metabolic rate of overweight and obese women.

Objectives: Obesity plays an important role in the development of chronic diseases including cardiovascular disease and diabetes. A low resting metabolic rate (RMR) for a given body size and composition is a risk factor for obesity, however, there is limited evidence available regarding the association of nutrient patterns and RMR. The aim of this study was to determine the association of nutrient patterns and RMR in overweight and obese women. Study design: This cross-sectional study was conducted on 360 women who were overweight or obese. Method: Dietary intake was assessed using a semi-quantitative standard food frequency questionnaire (FFQ). Nutrient patterns were also extracted by principal components analysis (PCA). All participants were evaluated for their body composition, RMR, and blood parameters. Result: Three nutrient patterns explaining 64% of the variance in dietary nutrients consumption were identified as B-complex-mineral, antioxidant, and unsaturated fatty acid and vitamin E (USFA-vit E) respectively. Participants were categorized into two groups based on the nutrient patterns. High scores of USFA-vit E pattern was significantly associated with the increase of RMR (β=0.13, 95% CI=0.79 to 68.16, p=0.04). No significant associations were found among B-complex-mineral pattern (β=-0.00, 95% CI=-49.67 to 46.03, p=0.94) and antioxidant pattern (β=0.03, 95% CI -41.42 to 22.59, p=0.56) with RMR. Conclusion: Our results suggested that the "USFA-vit E" pattern (such as PUFA, oleic, linoleic, vit.E, α-tocopherol and EPA) was associated with increased RMR.

Daily Changes of Resting Metabolic Rate in Elite Rugby Union Players

Preparation for competitive contact sport has been extensively researched. There are, however, limited data to guide players as to how the demands of their sport affect the energy requirements of recovery. We aimed to provide novel data on changes in resting metabolic rate (RMR) in contact sport athletes and relate these to the physical demands of training and competition. Twenty-two elite professional Premiership Rugby Union players were recruited to the study. Indirect calorimetry (Vyntus CPX canopy; CareFusion) was used to measure RMR each morning of the competitive game week, in a fasted, rested state. External loads for training and game play were monitored and recorded using global positioning systems (Catapult Innovations, Australia), whereas internal loads were tracked using rate of perceived exertion scales. Collisions were reviewed and recorded by expert video analysts for contacts in general play (breakdown and tackle area) or the set piece (scrum or maul). There were significant (P = 0.005) mean increases in RMR of approximately 231 kcal the morning after (game day [GD] + 1) and 3 d after the game (GD + 3), compared with the day before the game (GD - 1). The players were exposed to internal and external loads during the training week comparable to that of a match day; however, despite the equivocal loads between training and game play, there were no significant increases in RMR after training. The collisions experienced in rugby match play are likely to be responsible for the significant increases in RMR at GD + 1 and GD + 3. Consequently, the measurement of RMR via indirect calorimetry may provide a novel noninvasive measure of the effects of collisions. This study provides a novel insight to the energy requirements of recovering from contact sport.

Interactions between humidity and evaporative heat dissipation in a passerine bird.

Environmental humidity is thought to be a major determinant of evaporative cooling capacity at high air temperatures (Ta), but the technical challenges of experimentally manipulating humidity in respirometry chambers have resulted in far less being known about the effects of humidity compared to those of Ta. We tested the prediction that at Ta approaching and exceeding normothermic body temperature (Tb), high humidity would result in higher Tb, lower evaporative water loss (EWL) and/or higher resting metabolic rate (RMR) in a passerine bird, the white-browed sparrow-weaver (Plocepasser mahali). We used open-system flow-through respirometry to measure EWL, RMR and Tb in sparrow-weavers experiencing Ta = 36-44°C and chamber humidities of 6, 13, 19 or 25g m- 3. Increasing humidity was associated with significantly higher Tb. The strongest effect of humidity, however, involved significant increases in RMR; at Ta = 40°C, RMR at a humidity of 25g m- 3 was ~ 40% higher compared to a humidity of 6g m- 3. Moreover, the interaction between Ta and humidity exerted a significant effect on the ratio of evaporative heat loss (EHL) to metabolic heat production (MHP), evident as an increasing effect of humidity with increasing Ta. Our results, when compared with those of the limited number of previous studies that involved similar ranges of Ta and humidity, reveal that the relative effects of humidity on EWL and RMR vary among avian taxa, and support the notion that the overall effect of high humidity is a reduction in maximum EHL/MHP.

The Impact of Moderate Physical Activity on the Resting Metabolic Rate (RMR) in Children with Asthma

Objective – The objective was to assess whether a two week program of a moderate physical activity affects the resting metabolic rate (RMR) in a group of children with well-controlled asthma. Materials and methods - The study included 26 children (14 boys and 12 girls) aged 7-15 years, with well controlled asthma, who participated in Asthma Camp for a period of two weeks, where they had moderate physical activity on a daily basis. Body mass, height and RMR of the participants were measured on the first and last day of the Camp. The RMR assessment was based on a gas exchange measurement. Results – A statistically significant difference (P<0.05) between the two measurements was found for oxygen uptake (VO 2 ), expired oxygen content (FeO 2 ), RMR and % predicted Harris-Benedict, while there was no statistically significant difference for the respiratory minute ventilation, respiratory frequency and heart rate. Average RMR increased from 1244 kcal · day -1 to 1535 kcal · day -1 . Conclusion – Although most of the participants with asthma are in normal body weight range, there is still a significant proportion of overweight/obese participants. Average RMR of children with asthma was lower than expected by the HarrisBenedict equation. Two weeks of structured controlled moderate physical activity led to a significant increase in average RMR in both genders of children with asthma, reaching values higher than the Harris-Benedict estimation. Thereby, regular moderate physical activity should be an essential part of asthma treatment, especially in obese patients, since obesity is one of the most common co-morbidities in asthma.

Deep Brain Stimulation of the Hypothalamus Leads to Increased Metabolic Rate in Refractory Obesity

Obesity has become a worldwide epidemic, with very few long-term successful treatment options for refractory disease. Deep brain stimulation (DBS) of the bilateral lateral hypothalamus (LH) in refractory obesity has been performed safely. However, questions remain regarding the optimal settings and its effects on metabolic rate. The goals of our experiment were to determine the optimal DBS settings and the actual effect of optimal stimulation on energy expenditure. After bilateral LH DBS implantation, 2 subjects with treatment refractory obesity underwent 4 days of metabolic testing. The subjects slept overnight in a respiratory chamber to measure their baseline sleep energy expenditure, followed by 4 consecutive days of resting metabolic rate (RMR) testing at different stimulation settings. On day 4, the optimized DBS settings were used, and sleep energy expenditure was measured again overnight in the room calorimeter. During daily testing, the RMR fluctuated acutely with changes in stimulation settings and returned to baseline immediately after turning off the stimulation. Optimal stimulation settings selected for participants showed a 20% and 16% increase in RMR for the 2 participants. Overnight sleep energy expenditure measurements at these optimized settings on day 4 yielded a 10.4% and 4.8% increase over the baseline measurements for the 2 participants. These findings have demonstrated the efficacy of optimized DBS of the LH on increasing the RMR acutely and maintaining this increase during overnight sleep. These promising preliminary findings have laid the groundwork for the possible treatment of refractory obesity with DBS.

Pre-Sleep Consumption of Casein and Whey Protein: Effects on Morning Metabolism and Resistance Exercise Performance in Active Women.

Consuming milk proteins (casein (CP) and whey (WP)) at night before sleep has been shown to positively influence next morning resting metabolic rate (RMR). No data exist regarding the effect of pre-sleep consumption of CP and WP on the ability to perform resistance exercise (RE) the following morning. The present study compared the effects of low (24 g) and high (48 g) doses of CP and WP and a non-energetic placebo (PLA) consumed 30 min before sleep on morning RMR, and RE performance. Nine active women participated in this randomized, double-blind, crossover study. Next morning RMR was measured via indirect calorimetry. RE was performed on six machines for 2 sets of 10 repetitions, and a 3rd set to failure at 60% of one-repetition maximum to calculate RE volume (weight lifted × sets × repetitions). Magnitude based inferences were used. Compared to the PLA, 48 g CP had a likely increase in RMR (4.0 ± 4.8%) and possibly trivial (1.1 ± 7.0%) effect on RE volume. There were no clear effects of 24 g CP, 24 g and 48 g of WP on RMR and RE volume. In conclusion, 48 g CP elicited favorable changes in morning RMR, with only trivial changes in RE performance.

Geographic Variation in Larval Metabolic Rate Between Northern and Southern Populations of the Invasive Gypsy Moth.

Thermal regimes can diverge considerably across the geographic range of a species, and accordingly, populations can vary in their response to changing environmental conditions. Both local adaptation and acclimatization are important mechanisms for ectotherms to maintain homeostasis as environments become thermally stressful, which organisms often experience at their geographic range limits. The spatial spread of the gypsy moth (Lymantria dispar L.) (Lepidoptera: Erebidae) after introduction to North America provides an exemplary system for studying population variation in physiological traits given the gradient of climates encompassed by its current invasive range. This study quantifies differences in resting metabolic rate (RMR) across temperature for four populations of gypsy moth, two from the northern and two from southern regions of their introduced range in North America. Gypsy moth larvae were reared at high and low thermal regimes, and then metabolic activity was monitored at four temperatures using stop-flow respirometry to test for an acclimation response. For all populations, there was a significant increase in RMR as respirometry test temperature increased. Contrary to our expectations, we did not find evidence for metabolic adaptation to colder environments based on our comparisons between northern and southern populations. We also found no evidence for an acclimation response of RMR to rearing temperature for three of the four pairwise comparisons examined. Understanding the thermal sensitivity of metabolic rate in gypsy moth, and understanding the potential for changes in physiology at range extremes, is critical for estimating continued spatial spread of this invasive species both under current and potential future climatic constraints.

Avian thermoregulation in the heat: metabolism, evaporative cooling and gular flutter in two small owls.

The thermoregulatory responses of owls to heat stress have been the subject of few studies. Although nocturnality buffers desert-dwelling owls from significant heat stress during activity, roost sites in tree and cactus cavities or in deep shade provide only limited refuge from high environmental temperatures during the day. We measured thermoregulatory responses to acute heat stress in two species of small owls, the elf owl (Micrathene whitneyi) and the western screech-owl (Megascops kennicottii), which occupy the Sonoran Desert of southwestern North America, an area of extreme heat and aridity. We exposed wild-caught birds to progressively increasing air temperatures (Ta) and measured resting metabolic rate (RMR), evaporative water loss (EWL), body temperature (Tb) and heat tolerance limits (HTL; the maximum Ta reached). Comparatively low RMR values were observed in both species, Tb approximated Ta at 40°C and mild hyperthermia occurred as Ta was increased toward the HTL. Elf owls and screech-owls reached HTLs of 48 and 52°C, respectively, and RMR increased to 1.5 and 1.9times thermoneutral values. Rates of EWL at the HTL allowed for the dissipation of 167-198% of metabolic heat production (MHP). Gular flutter was used as the primary means of evaporative heat dissipation and produced large increases in evaporative heat loss (44-100%), accompanied by only small increases (<5%) in RMR. These small, cavity-nesting owls have thermoregulatory capacities that are intermediate between those of the open-ground nesting nightjars and the passerines that occupy the same ecosystem.

The energetic cost of mounting an immune response for Pallas's long-tongued bat (Glossophaga soricina).

The acute phase response (APR) is the first line of defense of the vertebrate immune system against pathogens. Mounting an immune response is believed to be energetically costly but direct measures of metabolic rate during immune challenges contradict this assumption. The energetic cost of APR for birds is higher than for rodents, suggesting that this response is less expensive for mammals. However, the particularly large increase in metabolic rate after APR activation for a piscivorous bat (Myotis vivesi) suggests that immune response might be unusually costly for bats. Here we quantified the energetic cost and body mass change associated with APR for the nectarivorous Pallas’s long-tongued bat (Glossophaga soricina). Activation of the APR resulted in a short-term decrease in body mass and an increase in resting metabolic rate (RMR) with a total energy cost of only 2% of the total energy expenditure estimated for G. soricina. This increase in RMR was far from the large increase measured for piscivorous bats; rather, it was similar to the highest values reported for birds. Overall, our results suggest that the costs of APR for bats may vary interspecifically. Measurement of the energy cost of vertebrate immune response is limited to a few species and further work is warranted to evaluate its significance for an animal’s energy budget.