Baseline Resting Metabolic Rate Research Articles

Higher baseline resting metabolic rate is associated with 1-year frailty decline among older adults residing in an urban area

BackgroundDysregulated energy metabolism is one hypothesized mechanism underlying frailty. Resting energy expenditure, as reflected by resting metabolic rate (RMR), makes up the largest component of total energy expenditure. Prior work relating RMR to frailty has largely been done in cross section with mixed results. We investigated whether and how RMR related to 1-year frailty change while adjusting for body composition.MethodsN = 116 urban, predominantly African-American older adults were recruited between 2011 and 2019. One-year frailty phenotype (0–5) was regressed on baseline RMR, frailty phenotype, demographics and body composition (DEXA) in an ordinal logistic regression model. Multimorbidity (Charlson comorbidity scale, polypharmacy) and cognitive function (Montreal Cognitive Assessment) were separately added to the model to assess for change to the RMR-frailty relationship. The model was then stratified by baseline frailty status (non-frail, pre-frail) to explore differential RMR effects across frailty.ResultsHigher baseline RMR was associated with worse 1-year frailty (odds ratio = 1.006 for each kcal/day, p = 0.001) independent of baseline frailty, demographics, and body composition. Lower fat-free mass (odds ratio = 0.88 per kg mass, p = 0.008) was independently associated with worse 1-year frailty scores. Neither multimorbidity nor cognitive function altered these relationships. The associations between worse 1-year frailty and higher baseline RMR (odds ratio = 1.009, p < 0.001) and lower baseline fat-free mass (odds ratio = 0.81, p = 0.006) were strongest among those who were pre-frail at baseline.DiscussionWe are among the first to relate RMR to 1-year change in frailty scores. Those with higher baseline RMR and lower fat-free mass had worse 1-year frailty scores, but these relationships were strongest among adults who were pre-frail at baseline. These relationships were not explained by chronic disease or impaired cognition. These results provide new evidence suggesting higher resting energy expenditure is associated with accelerate frailty decline.

Circadian Rhythms in Resting Metabolic Rate Account for Apparent Daily Rhythms in the Thermic Effect of Food.

ContextDaily variation in the thermic effect of food (TEF) is commonly reported and proposed as a contributing factor to weight gain with late eating. However, underlying circadian variability in resting metabolic rate (RMR) is an overlooked factor when calculating TEF associated with eating at different times of the day.ObjectiveThis work aimed to determine whether methodological approaches to calculating TEF contribute to the reported phenomena of daily variation in TEF.MethodsFourteen overweight to obese but otherwise healthy individuals had their resting and postprandial energy expenditure (EE) measured over 15.5 hours at a clinical research unit. TEF was calculated for breakfast, lunch, and dinner using standard methods (above a baseline and premeal RMR measure) and compared to a method incorporating a circadian RMR by which RMR was derived from a sinusoid curve model and TEF was calculated over and above the continuously changing RMR. Main outcome measures were TEF at breakfast, lunch, and dinner calculated by different methods.ResultsStandard methods of calculating TEF above a premeal measured RMR showed that morning TEF (60.8 kcal ± 5.6) (mean ± SEM) was 1.6 times greater than TEF at lunch (36.3 kcal ± 8.4) and 2.4 times greater than dinner TEF (25.2 kcal ± 9.6) (P = .022). However, adjusting for modeled circadian RMR nullified any differences between breakfast (54.1 kcal ± 30.8), lunch (49.5 kcal ± 29.4), and dinner (49.1 kcal ± 25.7) (P = .680).ConclusionDifferences in TEF between morning and evening can be explained by the underlying circadian resting EE, which is independent of an acute effect of eating.

Impact of Hepatic Steatosis on Resting Metabolic Rate and Metabolic Adaptation in Response to Intentional Weight Loss.

Weight loss is the primary intervention for nonalcoholic fatty liver disease (NAFLD). A decrease in resting metabolic rate (RMR) out of proportion to the degree of weight loss may promote weight regain. We aimed to determine the impact of hepatic steatosis on weight loss‐associated changes in RMR and metabolic adaptation, defined as the difference between predicted and measured RMR after weight loss. We retrospectively analyzed prospectively collected data from 114 subjects without diabetes (52 with NAFLD), with body mass index (BMI) >35, and who enrolled in a 6‐month weight loss intervention. Hepatic steatosis was determined by unenhanced computed tomography scans by liver:spleen attenuation ratio <1.1. RMR was measured by indirect calorimetry. At baseline, patients with hepatic steatosis had higher BMI, fat mass (FM), fat‐free mass (FFM), and RMR (RMR, 1,933 kcal/day; 95% confidence interval [CI], 841‐2,025 kcal/day; versus 1,696; 95% CI, 1,641‐1,751; P < 0.0001). After 6 months, the NAFLD group experienced larger absolute declines in weight, FM, and FFM, but percentage changes in weight, FFM, and FM were similar between groups. A greater decline in RMR was observed in patients with NAFLD (−179 kcal/day; 95% CI, −233 to −126 kcal/day; versus −100; 95% CI, −51 to −150; P = 0.0154) for the time × group interaction, and patients with NAFLD experienced greater metabolic adaptation to weight loss (−97 kcal/day; 95% CI, −143 to −50 kcal/day; versus −31.7; 95% CI, −74 to 11; P = 0.0218) for the prediction × group interaction. The change (Δ) in RMR was significantly associated with ΔFM, ΔFFM, and baseline RMR, while metabolic adaptation was significantly associated with female sex and ΔFM only. Conclusion: Hepatic steatosis is associated with a greater reduction in FM, which predicts RMR decline and a higher metabolic adaptation after weight loss, potentially increasing the risk of long‐term weight regain.

Estimation of non-shivering thermogenesis and cold-induced nutrient oxidation rates: Impact of method for data selection and analysis

Since the discovery of active brown adipose tissue in human adults, non-shivering cold-induced thermogenesis (CIT) has been regarded as a promising tool to combat obesity. However, there is a lack of consensus regarding the method of choice to analyze indirect calorimetry data from a CIT study. We analyzed the impact of methods for data selection and methods for data analysis on measures of cold-induced energy expenditure (EE) and nutrient oxidation rates. Forty-four young healthy adults (22.1±2.1 years old, 25.6±5.2kg/m2, 29 women) participated in the study. Resting metabolic rate (RMR), cold-induced thermogenesis (CIT), and cold-induced nutrient oxidation rates were estimated by indirect calorimetry under fasting conditions during 1h of cold exposure combining air conditioning (19.5-20°C) and a water perfused cooling vest set at a temperature of 4°C above the individual shivering threshold. We applied three methods for data selection: (i) time intervals every 5min (5min-TI), (ii) the most stable 5-min period of every forth part of the cold exposure (5min-SS-4P), and (iii) the most stable 5-min period of every half part of the cold exposure (5min-SS-2P). Lately we applied two methods for data analysis: (i) area under the curve as a percentage of the baseline RMR (AUC) and; (ii) the difference between EE at the end of the cold exposure and baseline RMR (Last-RMR). Mean overall CIT estimation ranged from 11.6±10.0 to 20.1±17.2 %RMR depending on the methods for data selection and analysis used. Regarding methods for data selection, 5min-SS-2P did not allow to observe physiologically relevant phenomena (e.g. metabolic shift in fuel oxidation; P=0.547) due to a lack of resolution. The 5min-TI and 5min-SS-4P methods for data selection seemed to be accurate enough to observe physiologically relevant phenomena (all P<0.014), but not comparable for estimating over-all CIT and cold-induced nutrient oxidation rates (P<0.01). Regarding methods for data analysis, the AUC seemed to be less affected for data artefacts and to be more representative in participants with a non-stable energy expenditure during cold exposure. The methods for data selection and analysis can have a profound impact on CIT and cold-induced nutrient oxidation rates estimations, and therefore, it is mandatory to unify it across scientific community to allow inter-study comparisons. Based on our findings, 5min-TI should be considered the method of choice to study dynamics (i.e. changes across time) of CIT and cold-induced nutrient oxidation rates, while 5min-SS-4P and AUC should be the method of choice when computing CIT and cold-induced nutrient oxidation rates as a single value.

The associations of resting metabolic rate with chronic conditions and weight loss.

The aim of this study was to examine the associations between baseline and changes in resting metabolic rate (RMR) with chronic condition(s) and weight loss (WL). Sex stratified analysis was undertaken on 393 adults from the Wharton Weight Management Clinics. The association between baseline RMR and WL was examined adjusting for age, BMI, ethnicity and treatment time. The association between changes in RMR (ΔRMR) and WL was also examined adjusting for baseline RMR and above covariates. Models were further adjusted for high glucose, triglycerides, blood pressure, low-density lipoprotein (LDL) and low high-density lipoprotein (HDL). While men (6.0 ± 8.6 kg) and women (5.6 ± 8.3 kg) had significant WL throughout the intervention, their measured decreases in RMR (-48 ± 322 kcal and -5 ± 322 kcal, respectively) were non-significant (P > 0.05). Individuals with a high blood pressure had a higher baseline RMR and women with a high LDL had a lower baseline RMR than those without the chronic condition (P < 0.05). Regardless of sex, WL was not significantly associated with baseline RMR or ΔRMR (P > 0.05) in both models. Participants with a low baseline RMR do not appear to be at a disadvantage for WL. Further, WL can occur without decreases in RMR in populations with high levels of obesity and obesity-related comorbidities.

Abstract 11438: Thyroid Hormones and Changes in Body Weight and Metabolic Parameters in Response to Weight-Loss Diets: The POUNDS LOST Trial

Context: The role of thyroid hormones in diet-induced weight loss and subsequent weight regain is largely unknown. Objective: To examine the relationship between baseline thyroid hormones and subsequent changes in body weight and resting metabolic rate (RMR) in a diet-induced weight-loss setting. Methods: In the 2-year POUNDS LOST randomized clinical trial that tested 4 weight-loss diets, thyroid hormones (free triiodothyronine [T3], free thyroxine [T4], total T3, total T4, and thyroid stimulating hormone [TSH]), and resting metabolic rate (RMR), as well as anthropometric and biochemical parameters, were determined at baseline, 6 months, and 2 years among 569 overweight and obese participants aged 30-70 years with normal thyroid function. Results: Participants lost an average of 6.6 kg of body weight during the first 6 months and subsequently regained an average of 2.7 kg of body weight over the remaining period from 6-24 months. Baseline free T3 and total T3 levels were positively associated with baseline body mass index and RMR, whereas free T4, total T4, and TSH did not demonstrate a clear pattern of correlations with these parameters. After multivariate adjustment including dietary intervention groups and baseline body weight, higher baseline free T3 and free T4 levels were significantly associated with a greater decrease in body weight in the first 6 months. Comparing extreme tertiles, the weight loss was -5.39±0.9 vs -3.87±0.9 for free T3 (P trend=0.02) and -5.88±0.9 vs -4.09±0.9 for free T4 (P trend=0.004). The thyroid hormones did not predict weight regain between 6 and 24 months. The associations were attenuated after further adjusting for changes in RMR. Conclusion: In this diet-induced weight-loss setting, higher baseline free T3 and free T4 predict more weight loss, but not weight regain among overweight and obese adults with normal thyroid function. In addition, changes in RMR may partially mediate the observed associations. These findings reveal a novel role of thyroid hormones in body weight regulations and may help identify individuals more responsive to weight-loss diets.

Less-than-expected weight loss in normal-weight women undergoing caloric restriction and exercise is accompanied by preservation of fat-free mass and metabolic adaptations.

Normal-weight women frequently restrict their caloric intake and exercise, but little is known about the effects on body weight, body composition and metabolic adaptations in this population. We conducted a secondary analysis of data from a randomized controlled trial in sedentary normal-weight women. Women were assigned to a severe energy deficit (SEV: -1062±80 kcal per day; n=9), a moderate energy deficit (MOD: -633±71 kcal per day; n=7) or energy balance (BAL; n=9) while exercising five times per week for 3 months. Outcome variables included changes in body weight, body composition, resting metabolic rate (RMR) and metabolic hormones associated with energy conservation. Weight loss occurred in SEV (-3.7±0.9 kg, P<0.001) and MOD (-2.7±0.8 kg; P=0.003), but weight loss was significantly less than predicted (SEV: -11.1±1.0 kg; MOD: -6.5±1.1 kg; both P<0.001 vs actual). Fat mass declined in SEV (P<0.001) and MOD (P=0.006), whereas fat-free mass remained unchanged in all groups (P>0.33). RMR decreased by -6±2% in MOD (P=0.020). In SEV, RMR did not change on a group level (P=0.66), but participants whose RMR declined lost more weight (P=0.020) and had a higher baseline RMR (P=0.026) than those whose RMR did not decrease. Characteristic changes in leptin (P=0.003), tri-iodothyronine (P=0.013), insulin-like growth factor-1 (P=0.016) and ghrelin (P=0.049) occurred only in SEV. The energy deficit and adaptive changes in RMR explained 54% of the observed weight loss. In normal-weight women, caloric restriction and exercise resulted in less-than-predicted weight loss. In contrast to previous literature, weight loss consisted almost exclusively of fat mass, whereas fat-free mass was preserved.

Overstated metabolic adaptation after “the biggest loser” intervention

TO THE EDITOR: The recent Obesity publication by Fothergill et al. (1) on the “The Biggest Loser” contestants (BLC) asserts that intensive exercise-centric intervention, despite fat-free mass (FFM) retention, leads to persistent metabolic adaptation (MA), thwarting long-term weight loss success. Their case rests upon predicting resting metabolic rate (RMR) using a newly developed, unvalidated, regression-derived equation [different from their previous equation in the same population (2)], with potentially error-prone weighted variables. The authors used baseline BLC data to predict RMR at subsequent time points in the same subjects. This is concerning, given the small sample (n = 16, which makes identifying four robust predictors statistically suspect), lack of validation in an independent sample, and the fact that the 1,000 kcal/day y-intercept is high compared with other established, validated equations. When we apply their data to these other equations, the predicted RMR is much lower and the apparent MA is less prominent. BLC exhibited unexpectedly elevated baseline RMR (+422 kcal) compared with gastric bypass controls matched for age, gender, weight, FFM, and fat mass (2). Anxiety, stress hormones, and weight gain before filming could have artificially elevated baseline RMR (3), thus inflating the apparent MA. Moreover, indirect calorimetry systems are not interchangeable (5); two different systems were used at baseline and 6 years with substantial, though statistically insignificant (1.96% ± 8.45%), inter-device bias. High variability in MaxII measures (supplemental data) warrants additional testing; the 2,600 kcal measure (−8% bias) likely upwardly skewed baseline RMR. DXA overestimates FFM in obesity because it cannot differentiate the intra- and extracellular water in normally hydrated adipose or lean tissue, nor excess extracellular water. Increased adipose water with obesity is not discernable from FFM. Overestimation of FFM would falsely elevate predicted RMR, enhancing perceived MA. Weight regain at 6 years could partly be adipose water and glycogen, potentially masking loss of metabolically active lean tissue. Another concern revolves around total energy expenditure; it simply does not agree with the measured RMR data. It is difficult to believe the authors' assertion that the BLC maintained the same intensive physical activity level (3+ h/day) at the 6-year mark as they had at competition end. Interestingly, previous modeling by Hall (4) described the exercise regimen as not sustainable. It is important to not lose sight of the fact that the BL intervention is quite extraordinary. The intensive nature of the exercise intervention sets it apart from more moderate weight loss regimens; it is unwise to extrapolate to all weight loss populations. Furthermore, media misinterpretation should be clarified. The BLC who maintained the most weight loss actually had greater metabolic slowing, which contradicts the idea that diet and exercise for weight loss are futile. In summary, methodological concerns and potential errors in key variables give pause to the authors' conclusions. Given the intense media attention garnered by these BL data, careful reconsideration is warranted, particularly in light of the public's willingness to accept headlines telling them exercise is useless as a weight-control strategy.

The effects of a fat loss supplement on resting metabolic rate and hemodynamic variables in resistance trained males: a randomized, double-blind, placebo-controlled, cross-over trial.

BackgroundWhile it is known that dietary supplements containing a combination of thermogenic ingredients can increase resting metabolic rate (RMR), the magnitude can vary based on the active ingredient and/or combination of active ingredients. The purpose of this study was to examine the effects of a commercially available thermogenic fat loss supplement on RMR and hemodynamic variables in healthy, resistance trained males.MethodsTen resistance-trained male participants (29 ± 9 years; 178 ± 4 cm; 85.7 ± 11 kg, and BMI = 26.8 ± 3.7) volunteered to participate in this randomized, double-blind, placebo controlled cross-over study. Participants underwent two testing sessions separated by at least 24 h. On their first visit, participants arrived to the laboratory after an overnight fast and a 24-h avoidance of exercise, and underwent a baseline RMR, HR, and BP assessment. Next, each participant ingested a thermogenic fat loss supplement (TFLS) or a placebo (PLA) and repeated the RMR, HR, and BP assessments at 60, 120, and 180 min post-ingestion. During the second visit the alternative supplement was ingested and the assessments were repeated in the exact same manner. Data were analyzed via a 2-factor [2x4] within-subjects repeated measures analysis of variance (ANOVA). Post-hoc tests were analyzed via paired samples t-tests. The criterion for significance was set at p ≤ 0.05.ResultsA significant main effect for time relative to raw RMR data (p = 0.014) was observed. Post-hoc analysis revealed that the TFLS significantly increased RMR at 60-min, 120-min, and 180-min post ingestion (p < 0.05) as compared to baseline RMR values. No significant changes in RMR were observed for the PLA treatment (p > 0.05). Specifically, RMR was increased by 7.8 % (from 1,906 to 2,057 kcal), 6.9 % (from 1,906 to 2,037 kcal), and 9.1 % (from 1,906 to 2,081 kcal) in the TFLS, while the PLA treatment increased RMR by 3.3 % (from 1,919 to 1,981 kcal), 3.1 % (from 1,919 to 1,978 kcal), and 2.1 % (from 1,919 to 1,959 kcal) above baseline at 60, 120, and 180-min post ingestion, respectively. Additionally, the TFLS significantly elevated RMR at the 3-h time point as compared to the PLA treatment (2,081 vs 1,959 kcal, p = 0.034). A main effect for groups was observed for systolic blood pressure, and a significant interaction and main effect for time were observed for diastolic blood pressure. It should be noted that although changes in diastolic blood pressure were significant, all values stayed within normal clinical ranges (<80 mmHg).ConclusionsThe TFLS led to significant elevations in RMR as compared to baseline. These elevations came with no adverse effect relative to resting heart rate, but a slight increase in blood pressure values. Taken on a daily basis, this TFLS may increase an individual’s overall energy expenditure, however; future studies should investigate if this leads to a reduction in fat mass loss over time.

The effects of a single-dose thermogenic supplement on resting metabolic rate and hemodynamic variables in healthy females--a randomized, double-blind, placebo-controlled, cross-over trial.

BackgroundRecent investigations have identified that commercially available dietary supplements, containing a combination of thermogenic ingredients, can increase resting metabolic rate (RMR). Thermogenic dietary supplements can have a positive influence on RMR, but the magnitude can vary based on the active ingredient and/or combination of active ingredients. Additionally, further safety evaluation is needed on multi-ingredient supplements that contain caffeine, due to its potential effect on heart rate (HR) and blood pressure (BP). The purpose of this study was to examine the effects of a commercially available dietary supplement on RMR and hemodynamic variables in healthy females.Methods13 female participants (26.1 ± 11.3 years; 163.4 ± 9.1 cm; 63.7 ± 8.0 kg, and 24 ± 5 BMI) volunteered to participate in this investigation. Participants underwent two testing sessions separated by approximately 7 days. On their first visit, participants arrived to the laboratory after an overnight fast and underwent a baseline RMR, HR, and BP assessment. Next, each participant ingested a thermogenic dietary supplement or placebo and repeated the RMR, HR, and BP assessments at 60, 120, and 180-minutes post-ingestion. Approximately 1-week later, the alternative supplement was ingested and the assessments were repeated in the exact same manner. Data were analyzed via a 2-factor [2x4] within-subjects repeated measures analysis of variance (ANOVA). Post-hoc tests were analyzed via paired samples t-tests.ResultsRepeated measures ANOVA revealed a significant effect for time relative to raw RMR data. Post-hoc analysis revealed that the dietary supplement treatment significantly increased RMR at 60-minutes, 120-minutes, and 180-minutes post ingestion (p < 0.05) as compared to baseline RMR values. No changes in RMR were observed for the placebo treatment (p > 0.05). Heart rate was not significantly affected at any time point with either supplement; however, main effects of treatment and time were observed for both systolic and diastolic blood pressure (p < 0.05).ConclusionsThe thermogenic dietary supplement treatment experienced greater elevations in RMR as compared to baseline. Due to the slight elevations in blood pressure, caution should be taken for those with increased risk for hypertension or pre-hypertension. Taken on a daily basis, thermogenic dietary supplementation may increase overall energy expenditure, potentially leading to reductions in fat mass over time.

The metabolic cost of mounting an immune response in male brown anoles (Anolis sagrei).

The tradeoff between reproduction and survival is central to life-history theory and is thought to reflect underlying energetic tradeoffs between reproduction and self-maintenance. Immune responses to parasites and pathogens are important components of self-maintenance in many species, but whether these defenses impose significant energetic costs has only been tested in a handful of organisms. We tested for a metabolic cost of mounting an immune response in the male brown anole (Anolis sagrei), a lizard in which we have previously shown that reproduction causes a marked reduction in immune response to the novel antigen phytohaemagglutinin (PHA). We treated captive male anoles with a subcutaneous injection of either PHA, which induces an immune response that manifests as localized swelling, or saline vehicle as a control. Prior to injection and at 24, 48, and 72 hr post-injection, we measured swelling at the site of injection and whole-animal resting metabolic rate (RMR) using stop-flow respirometry. Although we detected a robust swelling response to PHA at 24, 48, and 72 hr post-injection, mean RMR did not differ between treatments at any of these time points. However, within the PHA treatment group, RMR increased with the extent of swelling, suggesting a variable metabolic cost that scales with the magnitude of the induced immune response. Although individual anoles varied considerably in the extent to which they responded to PHA challenge, our results suggest that an immune response can impose a substantial metabolic cost (potentially as much as 63% above baseline RMR) for individuals that do respond maximally. J. Exp. Zool. 323A: 689-695, 2015. © 2015 Wiley Periodicals, Inc.

Energy Metabolism and the Burden of Multimorbidity in Older Adults: Results From the Baltimore Longitudinal Study of Aging.

Excessively elevated resting metabolic rate (RMR) for persons of a certain age, sex, and body composition is a mortality risk factor. Whether elevated RMR constitutes an early marker of health deterioration in older adult has not been fully investigated. Using data from the Baltimore Longitudinal Study of Aging, we hypothesized that higher RMR (i) was cross-sectionally associated with higher multimorbidity and (ii) predicted higher multimorbidity in subsequent follow-ups. The analysis included 695 Baltimore Longitudinal Study of Aging participants, aged 60 or older at baseline, of whom 248 had follow-up data available 2 years later and 109 four years later. Multimorbidity was assessed as number of chronic diseases. RMR was measured by indirect calorimetry and was tested in regression analyses adjusted for covariates age, sex, and dual-energy x-ray absorptiometry-measured total body fat mass and lean mass. Baseline RMR and multimorbidity were positively associated, independent of covariates (p = .002). Moreover, in a three-wave bivariate autoregressive cross-lagged model adjusted for covariates, higher prior RMR predicted greater future multimorbidity above and beyond the cross-sectional and autoregressive associations (p = .034). RMR higher than expected, given age, sex, and body composition, predicts future higher multimorbidity in older adults and may be used as early biomarker of impending health deterioration. Replication and the development of normative data are required for clinical translation.

Does H. pylori Colonization Impact Basal Metabolic Rate?

Introduction: Ghrelin is produced mainly by the stomach and may influence energy expenditure. H. pylori colonization is associated with reduced circulating ghrelin levels. We hypothesized that H. pylori colonization impacts resting metabolic rate (RMR). The aims of this study were to: 1.) evaluate the reproducibility of RMR measurements via a hand-held indirect calorimeter in healthy young adults, 2.) compare the RMR between individuals with and without H. pylori colonization, and 3.) analyze the change in RMR after H. pylori eradication. Methods: For the validation aim of the study, 7 healthy volunteers were enrolled and evaluated for demographic as well as clinical information. The MedGem indirect calorimeter device was used for all measurements. Weekly-standardized RMR and oxygen consumption (VO2) measurements were obtained for 4 consecutive weeks. For the second and third aims, 44 participants were evaluated at baseline for H. pylori status. All H. pylori-positive participants were treated with standard eradication regimens. RMR data was collected at baseline and subsequent follow-up visits (6 weeks, 3 months, and 6 months). Results: For the validation aim of the study, the pairwise correlations for weekly RMR measurements were all higher than 0.70, and the intra-class correlation coefficient (ICC) of the multiple measurements of RMR was 0.987 over 4 weeks. For the second and third aims, 17% of all participants were male, and the mean age was 24.57 years. The mean baseline BMI for all participants was 24.03. The mean baseline RMR for the H. pylori-negative and positive participants was 1297.8 and 1421.4, respectively. There was no significant difference in baseline RMR by H. pylori status (p=0.631). The absolute mean change in RMR from baseline to 6 weeks post treatment was greater for the H. pylori-positive group than the negative group (18.6 vs. -2.5), although not statistically significant. Similarly, the mean change in RMR from baseline to 3 months post treatment was greater for the H. pylori-positive group than the negative group (75.0 vs. 62.5). For the H. pylori-positive group, there was a significant difference between the mean RMR at baseline compared to the 3-month follow-up (p=0.034). Conclusion: Measurement of resting metabolic rate via a hand-held indirect calorimeter in young healthy adults is reproducible. H. pylori-colonization, as well as eradication, impacts RMR. Further assessment of the long-term metabolic consequences of H. pylori eradication should be undertaken.

Abstract 083: Role of Endoplasmic Reticulum Stress in the Subfornical Organ (SFO) in Fluid Balance and Metabolic Effects of Brain Renin-Angiotensin System (RAS) Activation

Endoplasmic reticulum (ER) stress has been identified as an important contributor to neurological diseases and implicated in mediating hypothalamic inflammation and the hypertensive effects of angiotensin II (AngII). We examined the role of ER stress in the metabolic and fluid balance effects of brain AngII in two mouse models: 1) sRA transgenic mice (expressing human renin in neurons and human angiotensinogen in glia and neurons), and 2) DOCA-salt treated C57BL/6J mice. Both DOCA-salt and sRA mice exhibit hyperactivity of the brain RAS, suppression of circulating RAS, hypertension, polydipsia, and an elevated resting metabolic rate (RMR). CCAAT-enhancer-binding protein homologous protein (CHOP), a marker of chronic ER stress, was examined by immunocytochemistry in the brain of both models. CHOP immunoreactivity was evident in the SFO of sRA and DOCA-salt mice but was absent in control and CHOP-/- mice. We infused the ER stress-reducing chemical chaperone tauroursodeoxycholic acid (TUDCA, 5.28 ug/day, or aCSF vehicle) to assess if ER stress is mechanistically related to the hypertension, polydipsia, and elevated RMR observed in both models. In initial studies, ICV TUDCA significantly attenuated the polydipsia (aCSF 20.7±0.9 vs TUDCA 10.8±1.0 mL/day, n=6,2) and RMR (aCSF, 3.38±0.07 vs TUDCA 3.16±0.06 mL O2/100g/min, P&lt;0.05 n=13,11) in the DOCA-salt model. ICV TUDCA had similar effects on the polydipsia in the sRA model (51±10% of aCSF control, P&lt;0.05 n=3,4). In the DOCA-salt model, daily ICV injections of TUDCA (10 days, 5ug/ul) markedly reduced drinking, but polydipsia returned one day after the injections were terminated (n=14,12). Daily ICV injection of another ER stress reducer 4-phenylbutyrate (5ug/ul) also reduced drinking (P&lt;0.05 n=5,4). To assess the functional role of CHOP, we measured RMR and water intake in CHOP-/- mice. Interestingly, CHOP-/- mice exhibited increased baseline RMR (CHOP-/- 0.161±0.010 vs C57 0.140±0.005 kcal/hr, P&lt;0.05 n=10,9). The increase in water intake in response to DOCA-salt was blunted (32.7±0.5 vs 22.8±1.1 ml/day, P&lt;0.05, n=4,5) in CHOP-/- mice. Together these data mechanistically implicate ER stress in the fluid and metabolic responses to increased brain RAS activity and suggest CHOP may play a functional role.

Elevated objectively measured but not self-reported energy intake predicts future weight gain in adolescents

Background: Although obesity putatively occurs when individuals consume more calories than needed for metabolic needs, numerous risk factor studies have not observed significant positive relations between reported caloric intake and future weight gain, potentially because reported caloric intake is inaccurate. Objective: The present study tested the hypothesis that objectively measured habitual energy intake, estimated with doubly labeled water, would show a stronger positive relation to future weight gain than self-reported caloric intake based on a widely used food frequency measure. Design: Two hundred and fifty-three adolescents completed a doubly labeled water (DLW) assessment of energy intake (EI), a food frequency measure, and a resting metabolic rate (RMR) assessment at baseline, and had their body mass index (BMI) measured at baseline and at 1- and 2-year follow-ups. Results: Controlling for baseline RMR, elevated objectively measured EI, but not self-reported habitual caloric intake, predicted increases in BMI over a 2-year follow-up. On average, participants under-reported caloric intake by 35%. Conclusions: Results provide support for the thesis that self-reported caloric intake has not predicted future weight gain because it is less accurate than objectively measured habitual caloric intake, suggesting that food frequency measures can lead to misleading findings. However, even objectively measured caloric intake showed only a moderate relation to future weight gain, implying that habitual caloric intake fluctuates over time and that it may be necessary to conduct serial assessments of habitual intake to better reflect the time-varying effects of caloric intake on weight gain.

Effects of Load-Volume on EPOC After Acute Bouts of Resistance Training in Resistance-Trained Men

Recent investigations have shown excess postexercise oxygen consumption (EPOC) to be elevated for up to 48 hours in both untrained and trained subjects after resistance training (RT). The purpose of this study was to investigate the effect of load-volume on EPOC. Eight trained men (aged 22 ± 3 years) participated in 2 randomized RT bouts separated by at least 1 week with total load-volumes of 10,000 and 20,000 kg, respectively. Intensity of RT (85% 1 repetition maximum) did not differ between trials. Exercise energy expenditure and resting metabolic rate (RMR) were measured by indirect calorimetry at 8.5 hours before, 1.5 hours before, and during RT bouts and 12, 24, 36, and 48 hours after exercise. Creatine kinase (CK) was measured before and after RT, and 12, 24, 36, and 48 hours postexercise; ratings of perceived muscle soreness were measured on a similar time course save the immediate postexercise time point. Analysis of variance with repeated measures was used to analyze dependent variables. During the 20,000 kg trial, subjects expended significantly (p < 0.01) more energy (484 ± 29 kcal) than the 10,000 kg lift (247 ± 18 kcal). After the 20,000 kg lift, 12 hours postexercise, CK (1,159 ± 729 U·L) was significantly elevated (p < 0.05) as compared with baseline (272 ± 280 U·L) and immediately postexercise (490 ± 402 U·L). No significant time or trial differences were found in RMR between the 10,000 and 20,000 kg trials. In conclusion, high-intensity RT with load-volumes of up to 20,000 kg using resistance-trained men does not significantly increase EPOC above baseline RMR.

Role of Baseline Leptin and Ghrelin Levels on Body Weight and Fat Mass Changes after an Energy-Restricted Diet Intervention in Obese Women: Effects on Energy Metabolism

Hormones related to energy balance control may play an important role on weight loss resistance after low-caloric diet (LCD) intervention. To investigate the predictive value of baseline leptin and ghrelin on body fat mass (FM) loss after 12 wk of LCD intervention and to study whether these associations could be related to changes in resting metabolic rate (RMR). The study comprised a total of 78 obese women (age 36.7 ± 7 yr). We measured, before and after the LCD intervention, FM (dual-energy x-ray absorptiometry) and RMR (kilojoules per kilogram body weight per day, indirect calorimetry). We also analyzed fasting serum leptin and ghrelin, and leptin to ghrelin ratio was calculated. FM and RMR changes (data at baseline - data after the intervention) were assessed. Baseline serum leptin (r = -0.301; age- and baseline FM-adjusted P = 0.009) and ghrelin (r = 0.314, adjusted P = 0.014) levels as well as leptin to ghrelin levels (r = -0.331; adjusted P = 0.009) were significantly correlated with FM changes. Leptin to ghrelin ratio was significantly correlated with RMR at baseline and after the LCD (both P < 0.010). Baseline leptin to ghrelin ratio significantly predicted changes in RMR after the LCD (r = 0.298; P = 0.019) regardless of age, baseline RMR, and total body weight (r = 0.307; P = 0.016) or FM loss (r = 0.312; P = 0.015). Obese women with higher leptin and lower ghrelin levels at baseline seem to be more resistant to FM loss. The leptin to ghrelin ratio could be proposed as a biomarker for predicting metabolic adaptations to energy restriction treatment and, if confirmed in future studies, as a predictor of treatment success/failure.

Energy metabolism of Inuit sled dogs

We explored how seasonal changes in temperature, exercise and food supply affected energy metabolism and heart rate of Inuit dogs in Greenland. Using open flow respirometry, doubly labeled water, and heart rate recording, we measured metabolic rates of the same dogs at two different locations: at one location the dogs were fed with high energy food throughout the year while at the other location they were fed with low energy food during summer. Our key questions were: is resting metabolic rate (RMR) increased during the winter season when dogs are working? Does feeding regime affect RMR during summer? What is the proportion of metabolic rate (MR) devoted to specific dynamic action (SDA), and what is the metabolic scope of working Inuit sled dogs? The Inuit dogs had an extremely wide thermoneutral zone extending down to -25 degrees C. Temperature changes between summer and winter did not affect RMR, thus summer fasting periods were defined as baseline RMR. Relative to this baseline, summer MR was upregulated in the group of dogs receiving low energy food, whereas heart rate was downregulated. However, during food digestion, both MR and HR were twice their respective baseline values. A continuously elevated MR was observed during winter. Because temperature effects were excluded and because there were also no effects of training, we attribute winter elevated MR to SDA because of the continuous food supply. Working MR during winter was 7.9 times the MR of resting dogs in winter, or 12.2 times baseline MR.

Interindividual variations in resting metabolic rate during weight loss in obese postmenopausal women: A pilot study

The objective of the study was to examine if decreases in resting metabolic rate (RMR) take place early in the weight loss process and if they remain throughout the duration of the weight loss intervention. Twenty obese postmenopausal women (61.8 ± 5.9 years) participated in a 15-week weight loss program. After the fifth week, subjects were characterized as having an increased (>5%) or a decreased (<5%) RMR based on baseline values. Afterward, they were followed for an additional 10 weeks. Outcome measures were as follows: fat mass ([FM] total, trunk), lean body mass (total, trunk), RMR, resting heart rate (RHR), and physical activity level. After 5 weeks, significant decreases were observed for lean body mass, FM, and RHR ( P < .05), whereas no overall changes in physical activity level and RMR were observed. However, on an individual basis, large variations in RMR were observed (ranging from −320 to +330 kcal/d). Analyses showed that subjects characterized as either having an increased or a decreased RMR after the fifth week maintained these adaptations at the end of intervention. Finally, subjects displaying a decreased RMR during weight loss had a significantly higher RMR and lower FM accumulations at baseline (total and trunk) compared with those with an increased RMR. Interindividual variations in RMR took place early in the weight loss process and were maintained over the duration of the weight loss program in our cohort of obese postmenopausal women. Baseline RMR, changes in RHR, and FM accumulations (total and trunk) seem to be important factors to consider when studying the effects of weight loss on RMR.

Low relative resting metabolic rate and body weight gain in adult Caucasian Italians

To investigate the relationship between resting metabolic rate (RMR) and subsequent changes in body size and degree of fatness in a group of adult Caucasian Italians. Prospective, longitudinal, observational study. In total, 155 subjects (72 males and 83 females, age range: 18-55 y; BMI: 17.5-63.4 kg/m2) were evaluated. In total, 43 (26 m and 17 f; BMI: 28.9+/-1.1 kg/m2, mean+/-s.e.m.) of them were reassessed 10-12 y later. Anthropometric and body composition (bioimpedance analysis) parameters and RMR (indirect calorimetry) were taken at baseline and after 10-12 y. Subjects (15 m, 8 f) who gained body weight (arbitrarily defined as a change in body weight > or = 5 kg) had baseline BMI (29.9+/-1.8 vs 28.0+/-1.4; P = NS) and body composition in terms of fat mass (FM%) and fat-free mass (FFM kg) comparable to those of the subjects (11 m, 9 f) whose body weight remained stable. Baseline RMR was significantly lower in subjects who gained weight than in those who did not (108+/-2.1 vs 122+/-3.1 kJ/kg-FFM 24 h; P < 0.001), although it did not differ significantly between the two groups (119+/-2 vs 121+/-2 kJ/kg-FFM 24 h; P = NS) 10-12 y later. Baseline RMR was inversely correlated to both change in body weight (r = -0.57; P < 0.001) and FM (r = -0.50; P < 0.001). A low RMR normalized for FFM appears to be associated with body weight gain in the long run in adult Caucasian Italians.