Indirect calorimetry protocol development for measuring resting metabolic rate as a component of total energy expenditure in free-living postmenopausal women

Development of New Predictive Equations for the Resting Metabolic Rate (RMR) of Women with Lipedema

This study aimed to develop a novel predictive equation for calculating resting metabolic rate (RMR) in women with lipedema. We recruited 119 women diagnosed with lipedema from the Angiology Outpatient Clinic at Wroclaw Medical University, Poland. RMR was assessed using indirect calorimetry, while body composition and anthropometric measurements were conducted using standardized protocols. Due to multicollinearity among predictors, classical multiple regression was deemed inadequate for developing the new equation. Therefore, we employed machine learning techniques, utilizing principal component analysis (PCA) for dimensionality reduction and predictor selection. Regression models, including support vector regression (SVR), random forest regression (RFR), and k-nearest neighbor (kNN) were evaluated in Python's scikit-learn framework, with hyperparameter tuning via GridSearchCV. Model performance was assessed through mean absolute percentage error (MAPE) and cross-validation, complemented by Bland-Altman plots for method comparison. A novel equation incorporating body composition parameters was developed, addressing a gap in accurate RMR prediction methods. By incorporating measurements of body circumference and body composition parameters alongside traditional predictors, the model's accuracy was improved. The segmented regression model outperformed others, achieving an MAPE of 10.78%. The proposed predictive equation for RMR offers a practical tool for personalized treatment planning in patients with lipedema.

Impact of methods for data selection on the day-to-day reproducibility of resting metabolic rate assessed with four different metabolic carts

BACKGROUND AND AIMS

Accomplishing a high day-to-day reproducibility is important to detect changes in resting metabolic rate (RMR) and respiratory exchange ratio (RER) that may be produced after an intervention or for monitoring patients' metabolism over time. We aimed to analyze: (i) the influence of different methods for selecting indirect calorimetry data on RMR and RER assessments; and, (ii) whether these methods influence RMR and RER day-to-day reproducibility.

METHODS AND RESULTS

Twenty-eight young adults accomplished 4 consecutive RMR assessments (30-min each), using the Q-NRG (Cosmed, Rome, Italy), the Vyntus CPX (Jaeger-CareFusion, Höchberg, Germany), the Omnical (Maastricht Instruments, Maastricht, The Netherlands), and the Ultima CardiO2 (Medgraphics Corporation, St. Paul, Minnesota, USA) carts, on 2 consecutive mornings. Three types of methods were used: (i) short (periods of 5 consecutive minutes; 6-10, 11-15, 16-20, 21-25, and 26-30 min) and long time intervals (TI) methods (6-25 and 6-30 min); (ii) steady state (SSt methods); and, (iii) methods filtering the data by thresholding from the mean RMR (filtering methods). RMR and RER were similar when using different methods (except RMR for the Vyntus and RER for the Q-NRG). Conversely, using different methods impacted RMR (all P ≤ 0.037) and/or RER (P ≤ 0.009) day-to-day reproducibility in all carts. The 6-25 min and the 6-30 min long TI methods yielded more reproducible measurements for all metabolic carts.

CONCLUSION

The 6-25 min and 6-30 min should be the preferred methods for selecting data, as they result in the highest day-to-day reproducibility of RMR and RER assessments.

The Effects of Intermittent Diet Breaks during 25% Energy Restriction on Body Composition and Resting Metabolic Rate in Resistance-Trained Females: A Randomized Controlled Trial

The purpose of this study was to examine the effects of intermittent versus continuous energy restriction on body composition, resting metabolic rate, and eating behaviors in resistance-trained females. Thirty-eight resistance-trained females (mean ± standard deviation age: 22.3±4.2 years) were randomized to receive either six weeks of a continuous 25% reduction in energy intake (n= 18), or one week of energy balance after every two weeks of 25% energy restriction (eight weeks total; n= 20). Participants were instructed to ingest 1.8 g protein/kilogram bodyweight per day and completed three weekly supervised resistance training sessions throughout the intervention. There were no differences between groups for changes over time in body composition, resting metabolic rate, or seven of the eight measured eating behavior variables (p > 0.05). However, a significant group-by-time interaction for disinhibition (p < 0.01) from the Three-Factor Eating Questionnaire was observed, with values (± standard error) in the continuous group increasing from 4.91 ± 0.73 to 6.17 ± 0.71, while values in the intermittent group decreased from 6.80 ± 0.68 to 6.05 ± 0.68. Thus, diet breaks do not appear to induce improvements in body composition or metabolic rate in comparison with continuous energy restriction over six weeks of dieting, but may be employed for those who desire a short-term break from an energy-restricted diet without fear of fat regain. While diet breaks may reduce the impact of prolonged energy restriction on measures of disinhibition, they also require a longer time period that may be less appealing for some individuals.

Comparison of Actual and Predicted Resting Metabolic Rate in Women with Lipedema

Background: An adequate dietary energy supply is particularly important in patients with lipedema as it promotes weight and fat loss. Accurate estimation of resting metabolic rate (RMR) allows implementing a proper calorie restriction diet in patients with lipedema. Our study aimed to compare actual resting metabolic rate (aRMR) with predicted resting metabolic rate (pRMR) in women with lipedema and to determine the association between individual body composition parameters, body mass index, and aRMR. Methods and Results: A total of 108 women diagnosed with lipedema were enrolled in the study. aRMR was obtained by indirect calorimetry (IC) using FitMate WM metabolic system (Cosmed, Rome, Italy). pRMR was estimated with predictive equations and bioelectric impedance analysis (BIA). All body composition parameters were based on BIA. The mean aRMR in the study group was 1705.2 ± 320.7 kcal/day. This study found the agreement of predictive equations compared to IC is low (<60%). Most methods of predicted RMR measurement used in our study significantly underpredicted aRMR in patients with lipedema. Therefore, the most applied equations remain useless in clinical practice in this specific population due to large individual differences among the studied women. Conclusions: IC is the best tool to evaluate RMR in evaluated patients with lipedema. It is necessary to propose a new equation to RMR determination in clinical practice.

Time to achieve steady state for an accurate assessment of resting energy expenditure in adolescents with healthy weight and obesity: A cross-sectional study

Objective

The present study investigated the time needed to achieve a steady state for an accurate assessment of resting energy expenditure (REE) in adolescents with healthy weight and obesity.

Methods

Thirty adolescents aged 12-17 years were assigned to a group with healthy weight (GHW; n = 12, body mass index [BMI] 22.5 ± 3.6 kg/m²) and another group with obesity (GO; n = 18, BMI 34.1 ± 5.2 kg/m²). Participants underwent test-retest reliability of REE assessment as follows: a) 24 h of abstention from physical exercise, soft drinks, or caffeine; b) fasting for ~12 h; c) acclimation period of 10 min; d) 30-min assessment in a supine position.

Results

A significant change occurred during the 30 min in REE. Significant differences existed between consecutive means until the 20^th and 25^th min for the GHW and GO, respectively. Although significant differences between trials 1 and 2 were detected during the first 5-10 min of assessment, the REE for each 5-min time point exhibited high test-retest reliability across trials in both groups (intraclass correlation coefficients range 0.79-0.99).

Conclusion

The following recommendations are provided to promote accurate assessment of REE among adolescents: a) initiate the REE assessment with 10 min of acclimation to decrease restlessness; b) determine REE for a minimum of 20 min if healthy weight and 25 min if obesity; c) determine REE for a further 5 min, with the average of this last 5 min of REE data being regarded as the REE.

The association of predicted resting energy expenditure with risk of breast cancer among postmenopausal women in the Women's Health Initiative cohort

Obesity and obesity-related metabolic disorders, such as obesity and chronic inflammation, have been positively associated both with postmenopausal breast cancer and with resting energy expenditure (REE). However, there is limited epidemiological evidence on the associations between REE and risk of postmenopausal breast cancer. We used multivariable Cox proportional hazards models to examine the association between predicted REE (calculated using the Ikeda, Livingston and Mifflin equations) and risk of postmenopausal breast cancer overall and by subtypes, and by level of body fat) among 137,305 postmenopausal women in the Women's Health Initiative (WHI). All predicted REEs were positively associated with risk of invasive breast cancer (HRq5 vs q1: 1.69; 95% CI: 1.57-1.81, HR: 1.69; 95% CI: 1.57-1.82 and HR: 1.68; 95% CI: 1.56-1.80 for Ikeda, Livingston and Mifflin, respectively). These positive associations were observed irrespective of the hormone receptor subtype, grade and stage of the tumors, but were most pronounced for estrogen receptor positive/progesterone receptor positive tumors. After additional adjustment for BMI, the associations were mostly attenuated and remained statistically significant for most of the outcomes. We also observed an interaction between the predicted REEs and BMI, with the associations being somewhat stronger among normal weight and overweight women than among obese women (pinteractions <0.05). Our findings indicate that relatively high REE is associated with increased risk of invasive breast cancer among postmenopausal women (particularly for the obesity-related tumor subtypes), irrespective of the equation used. Further studies using more objective measures of REE are, however, needed to confirm our findings.

APOΕ4 lowers energy expenditure in females and impairs glucose oxidation by increasing flux through aerobic glycolysis

Background

Cerebral glucose hypometabolism is consistently observed in individuals with Alzheimer’s disease (AD), as well as in young cognitively normal carriers of the Ε4 allele of Apolipoprotein E (APOE), the strongest genetic predictor of late-onset AD. While this clinical feature has been described for over two decades, the mechanism underlying these changes in cerebral glucose metabolism remains a critical knowledge gap in the field.

Methods

Here, we undertook a multi-omic approach by combining single-cell RNA sequencing (scRNAseq) and stable isotope resolved metabolomics (SIRM) to define a metabolic rewiring across astrocytes, brain tissue, mice, and human subjects expressing APOE4.

Results

Single-cell analysis of brain tissue from mice expressing human APOE revealed E4-associated decreases in genes related to oxidative phosphorylation, particularly in astrocytes. This shift was confirmed on a metabolic level with isotopic tracing of ¹³C-glucose in E4 mice and astrocytes, which showed decreased pyruvate entry into the TCA cycle and increased lactate synthesis. Metabolic phenotyping of E4 astrocytes showed elevated glycolytic activity, decreased oxygen consumption, blunted oxidative flexibility, and a lower rate of glucose oxidation in the presence of lactate. Together, these cellular findings suggest an E4-associated increase in aerobic glycolysis (i.e. the Warburg effect). To test whether this phenomenon translated to APOE4 humans, we analyzed the plasma metabolome of young and middle-aged human participants with and without the Ε4 allele, and used indirect calorimetry to measure whole body oxygen consumption and energy expenditure. In line with data from E4-expressing female mice, a subgroup analysis revealed that young female E4 carriers showed a striking decrease in energy expenditure compared to non-carriers. This decrease in energy expenditure was primarily driven by a lower rate of oxygen consumption, and was exaggerated following a dietary glucose challenge. Further, the stunted oxygen consumption was accompanied by markedly increased lactate in the plasma of E4 carriers, and a pathway analysis of the plasma metabolome suggested an increase in aerobic glycolysis.

Conclusions

Together, these results suggest astrocyte, brain and system-level metabolic reprogramming in the presence of APOE4, a ‘Warburg like’ endophenotype that is observable in young females decades prior to clinically manifest AD.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13024-021-00483-y.

A system for contact free energy expenditure assessment under free-living conditions: Monitoring metabolism for weight loss using carbon dioxide emission

Weight disorders are strikingly prevalent globally and can contribute to a wide array of potentially fatal diseases spanning from type II diabetes to coronary heart disease. These disorders have a common cause: poor calorie balance. Since energy expenditure (EE) [kcal/day] constitutes one half of the calorie balance equation (the other half being food intake), its measurement could be of great value to those suffering from weight disorders. A technique for contact free assessment of EE is presented, which only relies on CO2 concentration monitoring within a sealed office space, and assessment of carbon dioxide production rate (VCO2). Twenty healthy subjects were tested in a cross-sectional study to evaluate the performance of the aforementioned technique in measuring both resting energy expenditure (REE) and exercise energy expenditure using the proposed system (the "SmartPad") and a U.S. Food and Drug Administration (FDA) cleared gold standard reference instrument for EE measurement. For VCO2 and EE measurements, the method showed a correlation slope of 1.00 and 1.03 with regression coefficients of 0.99 and 0.99, respectively, and Bland-Altman plots with a mean bias = -0.232% with respect to the reference instrument. Furthermore, two subjects were also tested as part of a proof-of-concept longitudinal study where EE patterns were simultaneously tracked with body weight, sleep, stress, and step counts using a smartwatch over the course of a month, to determine correlation between the aforementioned parameters and EE. Analysis revealed moderately high correlation coefficients (Pearson's r) for stress (raverage=0.609) and body weight (raverage=0.597) for the 2 subjects. The new Smart Pad method was demonstrated to be a promising technique for energy expenditure measurement under free-living conditions.

The use of a portable metabolic monitoring device for measuring RMR in healthy adults

Objective measurement of RMR may be important for optimal nutritional care but is hindered by the price and practicality of the metabolic monitoring device. This study compared two metabolic monitoring devices for measuring RMR and VO2 and compared the measured RMR with the predicted RMR calculated from equations. RMR was measured using QUARK RMR (reference device) and Fitmate GS (COSMED) in a random order for 30 min, each on fasted participants. In total, sixty-eight adults participated (median age 22 years, interquartile range 21-32). Pearson correlation showed that RMR (r 0·86) and VO2 (r 0·86) were highly correlated between the two devices (P < 0·05). Intraclass correlation coefficients (ICC) showed good relative agreements regarding RMR (ICC = 0·84) and VO2 (ICC = 0·84) (P < 0·05). RMR measured by QUARK RMR was significantly higher (649 (sd 753) kJ/d) than Fitmate GS. Equations significantly overpredicted RMR. Accurate RMR (i.e. within ±10 % of the RMR measured by QUARK RMR) was found among 38 % of the participants for Fitmate GS and among 46-68 % depending on the equations. Bland-Altman analysis showed a low absolute agreement with QUARK RMR at an individual level for both Fitmate GS (limits of agreement (LOA): -828 to +2125 kJ/d) and equations (LOA ranged from -1979 to +1879 kJ/d). In conclusion, both Fitmate GS and predictive equations had low absolute agreements with QUARK RMR at an individual level. Therefore, these limitations should be considered when determining RMR using Fitmate GS or equations.

Extended Ketogenic Diet and Physical Training Intervention in Military Personnel

INTRODUCTION

Ketogenic diets (KDs) that elevate ketones into a range referred to as nutritional ketosis represent a possible nutrition approach to address the emerging physical readiness and obesity challenge in the military. An emerging body of evidence demonstrates broad-spectrum health benefits attributed to being in nutritional ketosis, but no studies have specifically explored the use of a KD in a military population using daily ketone monitoring to personalize the diet prescription.

MATERIALS AND METHODS

To evaluate the feasibility, metabolic, and performance responses of an extended duration KD, healthy adults (n = 29) from various military branches participated in a supervised 12-wk exercise training program. Fifteen participants self-selected to an ad libitum KD guided by daily measures of capillary blood ketones and 14 continued their normal mixed diet (MD). A battery of tests were performed before and after the intervention to assess changes in body mass, body composition, visceral fat, liver fat, insulin sensitivity, resting energy metabolism, and physical performance.

RESULTS

All KD subjects were in nutritional ketosis during the intervention as assessed by daily capillary beta-hydroxybutyrate (βHB) (mean βHB 1.2 mM reported 97% of all days) and showed higher rates of fat oxidation indicative of keto-adaptation. Despite no instruction regarding caloric intake, the KD group lost 7.7 kg body mass (range -3.5 to -13.6 kg), 5.1% whole-body percent fat (range -0.5 to -9.6%), 43.7% visceral fat (range 3.0 to -66.3%) (all p < 0.001), and had a 48% improvement in insulin sensitivity; there were no changes in the MD group. Adaptations in aerobic capacity, maximal strength, power, and military-specific obstacle course were similar between groups (p > 0.05).

CONCLUSIONS

US military personnel demonstrated high adherence to a KD and showed remarkable weight loss and improvements in body composition, including loss of visceral fat, without compromising physical performance adaptations to exercise training. Implementation of a KD represents a credible strategy to enhance overall health and readiness of military service members who could benefit from weight loss and improved body composition.

Measured resting metabolic rate, respiratory quotient, and body composition in patients with narcolepsy: a preliminary report of a case-control study

This case–control study compared the body composition, resting metabolic rate (RMR), and respiratory quotient (RQ) of narcolepsy patients with those of body mass index (BMI)- gender and age-matched controls. This study included 14 male patients with narcolepsy and 14 matched controls. The narcolepsy patients were subdivided into two subgroups (n = 7/each): those with cataplexy (NT1) and those without cataplexy (NT2). Anthropometric measurements, bioelectric impedance analysis, and indirect calorimetry were used in addition to the calculation of common body-composition indices (conicity index, abdominal volume index, and body adiposity index). Our results showed no significant difference in fat percentage, fat mass, fat-free mass, and TBW among NT1, NT2, and controls (p > 0.05). Compared to matched controls, there was a reduction of muscle mass in both NT1 and NT2 subgroups. The RMR was similar in all groups, while patients in the NT1/NT2 subgroups had a lower RQ, used more fat and fewer carbohydrates during the fasting period. These findings give an insight into the distinctive state of altered metabolism in patients with narcolepsy, especially the resting metabolic rate, which was not altered in NT1 vs. NT2 compared to the controls when matched for BMI, age, and gender.

Physiological, Psychological and Performance-Related Changes Following Physique Competition: A Case-Series

The purpose of this case-series was to evaluate the physiological, psychological and performance-related changes that occur during the postcompetition period. Participants included three male (34.3 ± 6.8 years, 181.6 ± 8.9 cm) and four female (29.3 ± 4.9 years, 161.4 ± 6.0 cm) natural physique athletes. Body composition (fat mass (FM) and fat-free mass (FFM); Skinfold), resting metabolic rate (RMR; indirect calorimetry), total body water (TBW; bioelectrical impedance analysis), sleep quality (PSQI; Pittsburgh Sleep Quality Index), quality of life measures (RAND SF36), menstrual irregularities, and knee extension performance were assessed 1-2 weeks prior to competition, and 4 weeks and 8-10 weeks postcompetition. Blood hormones (free triiodothyronine; T₃, free thyroxine; T₄, and leptin) were assessed at 1-2 weeks prior to competition and 8-10 weeks postcompetition. Participants tracked daily macronutrient intake daily for the duration of the study. Group-level data were analyzed using exploratory, one-tailed, nonparametric statistical tests. Bodyweight, FM, bodyfat%, RMR, and blood hormones (T₃, T₄, and leptin) increased significantly (p < 0.05) at the group level. Relative (%Δ) increases in fat mass were associated with △RMR (τ = 0.90; p = 0.001) and △leptin (τ = 0.68; p = 0.02), and △leptin was associated with △RMR (τ = 0.59; p = 0.03). The time course for recovery appears to vary substantially between individuals potentially due to strategies implemented postcompetition.

Intermittent Energy Restriction Attenuates the Loss of Fat Free Mass in Resistance Trained Individuals. A Randomized Controlled Trial

There is a lack of research into how lean, resistance trained (RT) individuals respond to intermittent energy restricted diets. Therefore, we investigated body composition changes in RT-individuals during continuous energy restriction or intermittent restriction. A total of 27 males and females (25 ± 6.1 years; 169 ± 9.4 cm; 80 ± 15.6 kg) were randomized to a ~25% caloric restricted diet Refeed (RF; n = 13) or Continuous group (CN; n = 14) in conjunction with 4-days/week resistance training for 7-weeks. RF implemented two consecutive days of elevated carbohydrate (CHO) intake, followed by 5-days of caloric restriction each week. CN adhered to a continuous 7-week caloric restriction. Body mass (BM), fat mass (FM), fat-free mass (FFM), dry fat-free mass (dFFM), and resting metabolic rate (RMR) were assessed pre/post-diet. Both groups significantly reduced BM (RF: baseline = 76.4 ± 15.6 kg, post-diet = 73.2 ± 13.8 kg, Δ3.2 kg; CN: baseline = 83.1 ± 15.4 kg, post-diet = 79.5 ± 15 kg, Δ3.6 kg) and FM (RF: baseline = 16.3 ± 4 kg, post-diet = 13.5 ± 3.6 kg, Δ2.8 kg; CN: baseline = 16.7 ± 4.5 kg, post-diet = 14.4 ± 4.9 kg, Δ2.3 kg) with no differences between groups. FFM (RF: baseline = 60.1 ± 13.8 kg, post-diet = 59.7 ± 13.0 kg, 0.4 kg; CN: baseline = 66.4 ± 15.2 kg, post-diet = 65.1 ± 15.2 kg, Δ1.3 kg p = 0.006), dFFM (RF: baseline = 18.7 ± 5.0 kg, post-diet = 18.5 ± 4.5 kg, Δ0.2 kg; CN: baseline =21.9 ± 5.7 kg, post-diet = 20.0 ± 5.7 kg, Δ1.9 kg), and RMR (RF: baseline = 1703 ± 294, post-diet = 1665 ± 270, Δ38 kcals; CN: baseline = 1867 ± 342, post-diet = 1789 ± 409, Δ78 kcals) were better maintained in the RF group. A 2-day carbohydrate refeed preserves FFM, dryFFM, and RMR during energy restriction compared to continuous energy restriction in RT-individuals.

Impact of the Method Used to Select Gas Exchange Data for Estimating the Resting Metabolic Rate, as Supplied by Breath-by-Breath Metabolic Carts

The method used to select representative gas exchange data from large datasets influences the resting metabolic rate (RMR) returned. This study determines which of three methods yields the lowest RMR (as recommended for use in human energy balance studies), and in which method the greatest variance in RMR is explained by classical determinants of this variable. A total of 107 young and 74 middle-aged adults underwent a 30 min RMR examination using a breath-by-breath metabolic cart. Three gas exchange data selection methods were used: (i) steady state (SSt) for 3, 4, 5, or 10 min, (ii) a pre-defined time interval (TI), i.e., 6–10, 11–15, 16–20, 21–25, 26–30, 6–25, or 6–30 min, and (iii) “filtering”, setting thresholds depending on the mean RMR value obtained. In both cohorts, the RMRs yielded by the SSt and filtering methods were significantly lower (p < 0.021) than those yielded by the TI method. No differences in RMR were seen under the different conditions of the SSt method, or of the filtering method. No differences were seen between the methods in terms of the variance in RMR explained by its classical determinants. In conclusion, the SSt and filtering methods return the lowest RMRs and intra-measurement coefficients of variation when using breath-by-breath metabolic carts.

Feasibility and Acceptability of Implementing Indirect Calorimetry Into Routine Clinical Care of Patients With Spinal Cord Injury

Background: In the absence of reliable predictive equations, indirect calorimetry (IC) remains the gold standard for assessing energy requirements after spinal cord injury (SCI), but it is typically confined to a research setting. The purpose of this study is to assess the feasibility and acceptability of implementing IC into routine clinical care in an Australian SCI rehabilitation facility. Methods: Bedside IC (canopy hood) was performed, and patients completed an IC acceptability questionnaire (open-ended; yes/no; 5-point Likert scale). Fasted resting energy expenditure (REE) steady-state criteria were applied to assess data quality, and adherence to a test ≥20 minutes was recorded. Staff were surveyed to assess impact of IC on usual care. Results: Of 35 eligible patients, 9 declined (7 reported claustrophobia). One patient could not be tested before discharge and 25 underwent IC (84% male, injury level C2-L2, AIS A-D). Anxiety prevented one patient from completing IC, while another failed to fast. The remaining 23 patients achieved a steady-state REE (≥5 consecutive minutes with ≤10% coefficient of variation for VO₂ and VCO₂). Test-retest (n = 5) showed <10% variation in REE. Patients deemed the procedure acceptable, with 88% reporting a willingness to repeat IC. Eighty percent of patients and 90% of staff agreed it was acceptable for IC to be integrated into usual care. Conclusion: This study found that IC is a feasible and acceptable addition to the routine clinical care of patients recovering from SCI and may serve to improve accuracy of nutrition interventions for this patient population.

High-Intensity Interval Training in Normobaric Hypoxia Leads to Greater Body Fat Loss in Overweight/Obese Women than High-Intensity Interval Training in Normoxia

A moderate hypoxic stimulus is considered a promising therapeutic modality for several pathological states including obesity. There is scientific evidence suggesting that when hypoxia and physical activity are combined, they could provide benefits for the obese population. The aim of the present study was to investigate if exposure to hypoxia combined with two different protocols of high-intensity interval exercise in overweight/obese women was more effective compared with exercise in normoxia. Study participants included 82 overweight/obese women, who started a 12 week program of 36 sessions, and were randomly divided into four groups: (1) aerobic interval training in hypoxia (AitH; FiO₂ = 17.2%; n = 13), (2) aerobic interval training in normoxia (AitN; n = 15), (3) sprint interval training in hypoxia (SitH; n = 15), and (4) sprint interval training in normoxia (SitN; n = 18). Body mass, body mass index, percentage of total fat mass, muscle mass, basal metabolic rate, fat, and carbohydrate oxidation, and fat and carbohydrate energy were assessed. Outcomes were measured at baseline (T1), after 18 training sessions (T2), 7 days after the last session (T3), and 4 weeks after the last session (T4). The fat mass in the SitH group was significantly reduced compared with the SitN group from T1 to T3 (p < 0.05) and from T1 to T4 (p < 0.05) and muscle mass increased significantly from T1 to T4 (p < 0.05). Fat mass in the AitH group decreased significantly (p < 0.01) and muscle mass increased (p = 0.022) compared with the AitN group from T1 to T4. All training groups showed a reduction in the percentage of fat mass, with a statistically significant reduction in the hypoxia groups (p < 0.05). Muscle mass increased significantly in the hypoxia groups (p < 0.05), especially at T4. While fat oxidation tended to increase and oxidation of carbohydrates tended to decrease in both hypoxia groups, the tendency was reversed in the normoxia groups. Thus, high-intensity interval training under normobaric intermittent hypoxia for 12 weeks in overweight/obese women seems to be promising for reducing body fat content with a concomitant increase in muscle mass.

Indirect calorimetry using a ventilated hood may be easier than using a facemask to achieve steady state when measuring resting energy expenditure

Previous studies have demonstrated differences in subjective comfort between different gas collecting methods during resting energy expenditure (REE) measurement. We hypothesized that gas collecting methods may have an influence on the time to achieve steady state and the optimum abbreviated period to estimate REE. Gas exchange variables were obtained using IIM-IC-100 (ventilated hood) and VO2000 (facemask) alternately among 32 healthy adults. A 10-minute test period was divided into 5-minute sliding time windows to obtain a subtle profile process of the coefficient of variation (CV) and REE. Friedman's test was used to compare the CVs during the test process. To compare the REE between abbreviated measurements and the reference, paired t test, linear regression, and Bland-Altman test were used. There were no significant differences between the CVs in each adjacent group of 5-minute intervals for IIM-IC-100 (P = .896). CV1 and CV2 were significantly higher than CV3-CV6 for VO2000 (P = .001). The proportion of subjects achieving steady state was lower with VO2000 (59.4-81.3%) than with IIM-IC-100 (84.4-91.8%). REE of the 2nd and 3rd 5-minute intervals did not differ from the reference, and they explained 94.7% (P < .001) and 94.9% (P < .001) of the last 5-minute REE variance, with the 95% limits of agreement ranging from -100.0 to 139.2 kcal/d and -139.5 to 182.5 kcal/d for IIM-IC-100 and VO2000, respectively. In conclusion, using a ventilated hood may be easier than using a facemask to achieve steady state and reduce the time required to estimate REE.

Measurement Methods for Physical Activity and Energy Expenditure: a Review

Physical activity is defined as any bodily movement produced by skeletal muscles that results in energy expenditure. The benefits of physical activity for health maintenance have been well documented, especially in the prevention and management of chronic diseases. Therefore, accurate measurement of physical activity and energy expenditure is essential both for epidemiological studies and in the clinical context. Given the large number of available methods, it is important to have an understanding of each, especially when one needs to choose a technique to use. The purpose of this review was to discuss the components of total energy expenditure and present advantage and limitations of different methods of physical activity and energy expenditure assessment.

Approximate Time to Steady-state Resting Energy Expenditure Using Indirect Calorimetry in Young, Healthy Adults

Indirect calorimetry (IC) measurements to estimate resting energy expenditure (REE) necessitate a stable measurement period or steady state (SS). There is limited evidence when assessing the time to reach SS in young, healthy adults. The aims of this prospective study are to determine the approximate time to necessary reach SS using open-circuit IC and to establish the appropriate duration of SS needed to estimate REE. One hundred young, healthy participants (54 males and 46 females; age = 20.6 ± 2.1 years; body weight = 73.6 ± 16.3 kg; height 172.5 ± 9.3 cm; BMI = 24.5 ± 3.8 kg/m²) completed IC measurement for approximately 30 min while the volume of oxygen (VO₂) and volume of carbon dioxide (VCO₂) were collected. SS was defined by variations in the VO₂ and VCO₂ of ≤10% coefficient of variation (%CV) over a period of five consecutive minutes. The 30-min IC measurement was divided into six 5-min segments, such as S1, S2, S3, S4, S5, and S6. The results show that SS was achieved during S2 (%CV = 6.81 ± 3.2%), and the %CV continued to met the SS criteria for the duration of the IC measurement (S3 = 8.07 ± 4.4%, S4 = 7.93 ± 3.7%, S5 = 7.75 ± 4.1%, and S6 = 8.60 ± 4.6%). The current study found that in a population of young, healthy adults the duration of the IC measurement period could be a minimum of 10 min. The first 5-min segment was discarded, while SS occurred by the second 5-min segment.

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

BACKGROUND

While 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.

METHODS

Ten 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.

RESULTS

A 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).

CONCLUSIONS

The 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

BACKGROUND

Recent 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.

METHODS

13 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.

RESULTS

Repeated 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).

CONCLUSIONS

The 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.

Personalised Prescription of Scalable High Intensity Interval Training to Inactive Female Adults of Different Ages

Stepping is a convenient form of scalable high-intensity interval training (HIIT) that may lead to health benefits. However, the accurate personalised prescription of stepping is hampered by a lack of evidence on optimal stepping cadences and step heights for various populations. This study examined the acute physiological responses to stepping exercise at various heights and cadences in young (n = 14) and middle-aged (n = 14) females in order to develop an equation that facilitates prescription of stepping at targeted intensities. Participants completed a step test protocol consisting of randomised three-minute bouts at different step cadences (80, 90, 100, 110 steps·min^-1) and step heights (17, 25, 30, 34 cm). Aerobic demand and heart rate values were measured throughout. Resting metabolic rate was measured in order to develop female specific metabolic equivalents (METs) for stepping. Results revealed significant differences between age groups for METs and heart rate reserve, and within-group differences for METs, heart rate, and metabolic cost, at different step heights and cadences. At a given step height and cadence, middle-aged females were required to work at an intensity on average 1.9 ± 0.26 METs greater than the younger females. A prescriptive equation was developed to assess energy cost in METs using multilevel regression analysis with factors of step height, step cadence and age. Considering recent evidence supporting accumulated bouts of HIIT exercise for health benefits, this equation, which allows HIIT to be personally prescribed to inactive and sedentary women, has potential impact as a public health exercise prescription tool.

Simultaneous association of total energy consumption and activity-related energy expenditure with risks of cardiovascular disease, cancer, and diabetes among postmenopausal women

Total energy consumption and activity-related energy expenditure (AREE) estimates that have been calibrated using biomarkers to correct for measurement error were simultaneously associated with the risks of cardiovascular disease, cancer, and diabetes among postmenopausal women who were enrolled in the Women's Health Initiative at 40 US clinical centers and followed from 1994 to the present. Calibrated energy consumption was found to be positively related, and AREE inversely related, to the risks of various cardiovascular diseases, cancers, and diabetes. These associations were not evident in most corresponding analyses that did not correct for measurement error. However, an important analytical caveat relates to the role of body mass index (BMI) (weight (kg)/height (m)(2)). In the calibrated variable analyses, BMI was regarded, along with self-reported data, as a source of information on energy consumption and physical activity, and BMI was otherwise excluded from the disease risk models. This approach cannot be fully justified with available data, and the analyses herein imply a need for improved dietary and physical activity assessment methods and for longitudinal self-reported and biomarker data to test and relax modeling assumptions. Estimated hazard ratios for 20% increases in total energy consumption and AREE, respectively, were as follows: 1.49 (95% confidence interval: 1.18, 1.88) and 0.80 (95% confidence interval: 0.69, 0.92) for total cardiovascular disease; 1.43 (95% confidence interval: 1.17, 1.73) and 0.84 (95% confidence interval: 0.73, 0.96) for total invasive cancer; and 4.17 (95% confidence interval: 2.68, 6.49) and 0.60 (95% confidence interval: 0.44, 0.83) for diabetes.

Validity Test of a New Open-Circuit Indirect Calorimeter

BACKGROUND

Indirect calorimetry is an accurate way to measure resting metabolic rate. The Deltatrac Metabolic Monitor is considered a criterion standard but is no longer manufactured. New-generation indirect calorimeters have been introduced, but there are limited published validation data comparing these devices to criterion instruments.

MATERIALS AND METHODS

A prospective, observational, N-of-1 trial was conducted to validate a new-generation indirect calorimeter against a gold standard device. This design was chosen to minimize and define the degree of biological variation, thus focusing on variation due to the devices. Measurements of gas exchange using both indirect calorimeters were conducted daily for 10 consecutive days. Another set of measurement pairs was conducted using just the criterion device for 10 days. Ninety-five percent confidence intervals of differences were used to test for bias. Precision was defined as repeat measures with one device falling within 5% of the other at least 90% of the time.

RESULTS

There were no statistically significant differences between the devices for any measured or calculated parameter. Interdevice differences were no larger than intradevice differences using the criterion instrument. The values obtained from the new device were precise and unbiased compared with the values obtained from the gold standard device.

CONCLUSION

The new indirect calorimeter measures gas exchange in a reliable and accurate manner compared with a gold standard device. The two devices are equivalent.

An exploratory study of respiratory quotient calibration and association with postmenopausal breast cancer

BACKGROUND

The respiratory quotient (RQ), defined as the ratio of carbon dioxide exhaled to oxygen uptake, reflects substrate utilization when energy is expended. Fat and alcohol have RQ values of approximately 0.7, compared with 1.0 for carbohydrate, and approximately 0.8 for protein. Here, the association between RQ and postmenopausal breast cancer risk is studied.

METHODS

Paired RQ measurements were obtained, separated by approximately 6 months, for women in the reliability subset of a Women's Health Initiative (WHI) Nutrition and Physical Activity Assessment Study. Linear regression of the average of the paired log RQ assessments on a corresponding log food quotient (FQ) average and other study subject characteristics, including age, body mass index, race, and education, yielded calibration equations for predicting RQ.

RESULTS

Calibration equations, using any of food frequency, food record, or dietary recall data, explained an appreciable fraction of measured log RQ variation, and these were used to compute calibrated RQ estimates throughout WHI cohorts. Calibrated RQ estimates using 4-day food record (4DFR) data related inversely (P = 0.004) to (invasive) breast cancer risk in the WHI Dietary Modification trial comparison group, and corresponding RQ estimates using food-frequency data related inversely (P = 0.002) to breast cancer incidence in this cohort combined with the larger WHI observational study.

CONCLUSION

Although preliminary, these analyses suggest a substantially higher postmenopausal breast cancer risk among women having relatively low RQ.

IMPACT

RQ elevation could provide a novel target for breast cancer risk reduction.

Comparison of predictive equations and measured resting energy expenditure among obese youth attending a pediatric healthy weight clinic: one size does not fit all

BACKGROUND

The Academy of Nutrition and Dietetics recommends the use of indirect calorimetry for calculating caloric targets for weight loss in obese youth. Practitioners typically use predictive equations since indirect calorimetry is often not available. The objective of this study was to compare measured resting energy expenditure (MREE) with that estimated using published predictive equations in obese pediatric patients.

MATERIAL AND METHODS

Youth aged 7 to 18 years (n = 80) who were referred to a university-based healthy weight clinic and who were greater than the 95th percentile BMI for age and gender participated. MREE was measured via a portable indirect calorimeter. Predicted energy expenditure (pEE) was estimated using published equations including those commonly used in children. pEE was compared to the MREE for each subject. Absolute mean difference between MREE and pEE, mean percentage accuracy, and mean error were determined.

RESULTS

Mean percentage accuracy of pEE compared with MREE varied widely, with the Harris-Benedict, Lazzer, and Molnar equations providing the greatest accuracy (65%, 61%, and 60%, respectively). Mean differences between MREE and equation-estimated caloric targets varied from 197.9 kcal/day to 307.7 kcal/day.

CONCLUSIONS

The potential to either overestimate or underestimate calorie needs in the clinical setting is significant when comparing EE derived from predictive equations with that measured using portable indirect calorimetry. While our findings suggest that the Harris-Benedict equation has improved accuracy relative to other equations in severely obese youth, the potential for error remains sufficiently great to suggest that indirect calorimetry is preferred.

Comparison of heart and respiratory rate variability measures using an intermittent incremental submaximal exercise model

To better understand the alterations in cardiorespiratory variability during exercise, the present study characterized the patterns of change in heart rate variability (HRV), respiratory rate variability (RRV), and combined cardiorespiratory variability (HRV-RRV) during an intermittent incremental submaximal exercise model. Six males and six females completed a submaximal exercise protocol consisting of an initial baseline resting period followed by three 10-min bouts of exercise at 20%, 40%, and 60% of maximal aerobic capacity (V̇O2max). The R-R interval and interbreath interval variability were measured at baseline rest and throughout the submaximal exercise. A group of 93 HRV, 83 RRV, and 28 HRV-RRV measures of variability were tracked over time through a windowed analysis using a 5-min window size and 30-s window step. A total of 91 HRV measures were able to detect the presence of exercise, whereas only 46 RRV and 3 HRV-RRV measures were able to detect the same stimulus. Moreover, there was a loss of overall HRV and RRV, loss of complexity of HRV and RRV, and loss of parasympathetic modulation of HRV (up to 40% V̇O2max) with exercise. Conflicting changes in scale-invariant structure of HRV and RRV with increases in exercise intensity were also observed. In summary, in this simultaneous evaluation of HRV and RRV, we found more consistent changes across HRV metrics compared with RRV and HRV-RRV.

Physical activity assessment: biomarkers and self-report of activity-related energy expenditure in the WHI

We used a biomarker of activity-related energy expenditure (AREE) to assess measurement properties of self-reported physical activity and to determine the usefulness of AREE regression calibration equations in the Women's Health Initiative. Biomarker AREE, calculated as the total energy expenditure from doubly labeled water minus the resting energy expenditure from indirect calorimetry, was assessed in 450 Women's Health Initiative participants (2007-2009). Self-reported AREE was obtained from the Arizona Activity Frequency Questionnaire (AAFQ), the 7-Day Physical Activity Recall (PAR), and the Women's Health Initiative Personal Habits Questionnaire (PHQ). Eighty-eight participants repeated the protocol 6 months later. Reporting error, measured as log(self-report AREE) minus log(biomarker AREE), was regressed on participant characteristics for each instrument. Body mass index was associated with underreporting on the AAFQ and PHQ but overreporting on PAR. Blacks and Hispanics underreported physical activity levels on the AAFQ and PAR, respectively. Underreporting decreased with age for the PAR and PHQ. Regressing logbiomarker AREE on logself-reported AREE revealed that self-report alone explained minimal biomarker variance (R(2) = 7.6, 4.8, and 3.4 for AAFQ, PAR, and PHQ, respectively). R(2) increased to 25.2, 21.5, and 21.8, respectively, when participant characteristics were included. Six-month repeatability data adjusted for temporal biomarker variation, improving R(2) to 79.4, 67.8, and 68.7 for AAFQ, PAR, and PHQ, respectively. Calibration equations "recover" substantial variation in average AREE and valuably enhance AREE self-assessment.

Influence of weight classification on walking and jogging energy expenditure prediction in women

The purpose of this study was to determine the influence of weight classification on predicting energy expenditure (EE) in women. Twelve overweight (body mass index [BMI] = 25-29.99 kg/m(2)) and 12 normal-weight (BMI = 18.5-24.99 kg/m(2)) women walked and jogged 1,609 m at 1.34 ms(-1) and 2.23 ms(-1), respectively, while EE was assessed using indirect calorimetry and compared to several other prediction methods (American College of Sports Medicine [ACSM], 2010; Heyward, 2006; Léger & Mercier, 1984; McArdle, Katch, & Katch, 2006; Pandolf Givoni, & Goldman, 1978; van der Walt & Wyndham, 1973). More error occurred with overweight EE prediction compared to normal-weight EE prediction. The ACSM and Heyward methods for walking and the McArdle et al. method for jogging most accurately predicted EE for both groups. Weight classification influences EE prediction accuracy and, thus, is important to consider when using these prediction methods.

Relationship between long sleep duration and functional capacities in postmenopausal women

STUDY OBJECTIVE

The purpose of the present study was to examine the relationship between long sleep duration and functional capacities.

METHODS

We conducted a cross-sectional study at the Department of Kinanthropology at the University of Quebec at Montreal. Forty eight non-frail postmenopausal women aged between 49 to 75 years were recruited using advertisements in local papers. Body weight, body mass index, fat mass, skeletal muscle mass, number of steps per day, SF-36 total (healthy questionnaire), resting metabolic rate, total energy intake, sleep duration, knee extensor strength (dynamometer), chair stand test and balance opened eyes test were measured.

RESULTS

WE FOUND A SIGNIFICANT NEGATIVE CORRELATION BETWEEN HOURS OF SLEEP AND FUNCTIONAL CAPACITY: chair stand test (r = -0.33, p = 0.02), balance opened eyes test (r = -0.45, p = 0.001), muscle strength (r = -0.43, p = 0.002) and skeletal muscle mass (r = -0.39, p = 0.007). In addition, long sleepers (> 9 h) had significantly lower values for skeletal muscle mass (p = 0.03), muscle strength (p = 0.01), chair stand test (p = 0.03), and balance opened eyes test (p = 0.001). Finally, linear regression analysis showed that sleep duration was an independent predictor of the chair stand test (p = 0.024), balance opened eyes test (p = 0.001), and muscle strength (p = 0.035) in our cohort.

CONCLUSION

Long sleepers were associated with lower functional capacities in our cohort of sedentary postmenopausal women.

Effects of supplemental fish oil on resting metabolic rate, body composition, and salivary cortisol in healthy adults

Background

To determine the effects of supplemental fish oil (FO) on resting metabolic rate (RMR), body composition, and cortisol production in healthy adults.

Methods

A total of 44 men and women (34 ± 13y, mean+SD) participated in the study. All testing was performed first thing in the morning following an overnight fast. Baseline measurements of RMR were measured using indirect calorimetry using a facemask, and body composition was measured using air displacement plethysmography. Saliva was collected via passive drool and analyzed for cortisol concentration using ELISA. Following baseline testing, subjects were randomly assigned in a double blind manner to one of two groups: 4 g/d of Safflower Oil (SO); or 4 g/d of FO supplying 1,600 mg/d eicosapentaenoic acid (EPA) and 800 mg/d docosahexaenoic acid (DHA). All tests were repeated following 6 wk of treatment. Pre to post differences were analyzed using a treatment X time repeated measures ANOVA, and correlations were analyzed using Pearson's r.

Results

Compared to the SO group, there was a significant increase in fat free mass following treatment with FO (FO = +0.5 ± 0.5 kg, SO = -0.1 ± 1.2 kg, p = 0.03), a significant reduction in fat mass (FO = -0.5 ± 1.3 kg, SO = +0.2 ± 1.2 kg, p = 0.04), and a tendency for a decrease in body fat percentage (FO = -0.4 ± 1.3% body fat, SO = +0. 3 ± 1.5% body fat, p = 0.08). No significant differences were observed for body mass (FO = 0.0 ± 0.9 kg, SO = +0.2 ± 0.8 kg), RMR (FO = +17 ± 260 kcal, SO = -62 ± 184 kcal) or respiratory exchange ratio (FO = -0.02 ± 0.09, SO = +0.02 ± 0.05). There was a tendency for salivary cortisol to decrease in the FO group (FO = -0.064 ± 0.142 μg/dL, SO = +0.016 ± 0.272 μg/dL, p = 0.11). There was a significant correlation in the FO group between change in cortisol and change in fat free mass (r = -0.504, p = 0.02) and fat mass (r = 0.661, p = 0.001).

Conclusion

6 wk of supplementation with FO significantly increased lean mass and decreased fat mass. These changes were significantly correlated with a reduction in salivary cortisol following FO treatment.

The effect of exercise training on resting metabolic rate in type 2 diabetes mellitus

PURPOSE

Exercise is a possible means to increase resting energy expenditure, which could offset age-related metabolic declines and facilitate weight management, both of which are particularly important for people who have type 2 diabetes mellitus. We sought to determine the effects of aerobic exercise training and resistance exercise training and the incremental effect of combined aerobic and resistance exercise training on resting metabolic rate (RMR) in previously sedentary individuals with type 2 diabetes.

METHODS

After a 4-wk run-in period, 103 participants (72 male, 31 female, 39-70 yr, mean +/- SD body mass index = 32.9 +/- 5.7 kg x m(-2)) were randomly assigned to four groups for 22 wk: aerobic training, resistance training, combined aerobic and resistance exercise training, or waiting-list control. Exercise training was performed three times per week at community-based gym facilities. RMR was measured by indirect calorimetry for 30 min after an overnight fast. Body composition was assessed using bioelectrical impedance. These measurements were taken at baseline, at 3 months, and at 6 months of the intervention.

RESULTS

RMR did not change significantly in any group after accounting for multiple comparisons despite significant improvements in peak oxygen consumption and muscular strength in the exercising groups. Adjusting RMR for age, sex, fat mass, and fat-free mass in various combinations did not alter these results.

CONCLUSION

These results suggest that RMR was not significantly changed after a 6-month exercise program, regardless of modality, in this sample of adults with type 2 diabetes.

Assessment of physical activity using accelerometry, an activity diary, the heart rate method and the Indian migration study questionnaire in south Indian adults

OBJECTIVE

To validate questionnaire-based physical activity level (PAL) against accelerometry and a 24 h physical activity diary (24 h AD) as reference methods (Protocol 2), after validating these reference methods against the heart rate-oxygen consumption (HRVO2) method (Protocol 1).

DESIGN

Cross-sectional study.

SETTING

Two villages in Andhra Pradesh state and Bangalore city, South India.

SUBJECTS

Ninety-four participants (fifty males, forty-four females) for Protocol 2; thirteen males for Protocol 1.

RESULTS

In Protocol 2, mean PAL derived from the questionnaire (1.72 (sd 0.20)) was comparable to that from the 24 h AD (1.78 (sd 0.20)) but significantly higher than the mean PAL derived from accelerometry (1.36 (sd 0.20); P < 0.001). Mean bias of PAL from the questionnaire was larger against the accelerometer (0.36) than against the 24 h AD (-0.06), but with large limits of agreement against both. Correlations of PAL from the questionnaire with that of the accelerometer (r = 0.28; P = 0.01) and the 24 h AD (r = 0.30; P = 0.006) were modest. In Protocol 1, mean PAL from the 24 h AD (1.65 (sd 0.18)) was comparable, while that from the accelerometer (1.51 (sd 0.23)) was significantly lower (P < 0.001), than mean PAL obtained from the HRVO2 method (1.69 (sd 0.21)).

CONCLUSIONS

The questionnaire showed acceptable validity with the reference methods in a group with a wide range of physical activity levels. The accelerometer underestimated PAL in comparison with the HRVO2 method.

Validation of three predictive equations for basal metabolic rate in adults

Objective

To cross-validate three predictive set of equations for basal metabolic rate (BMR) developed by Schofield (Schofield database), Henry (Oxford database) and Cole (Oxford database) using mean values for age, weight, height and BMR of published studies.

Design

Literature review of studies published from 1985 to March 2002.

Setting

All studies selected used appropriate methods and followed conditions that met the criteria established for basal metabolism, were performed in healthy adults, and were not part of the Schofield or Oxford database.

Subjects

A total of 261 groups of men and women from 175 studies were selected and categorised in three age groups (18.5–29.9, 30.0–59.9, ≥60 years old) and three body mass index (BMI) groups (normal weight, overweight and obese).

Results

Linear regression and concordance correlation analysis showed that the three sets of equations had the same association and agreement with measured BMR, across gender, age, and BMI groups. The agreement of all equations was moderate for men and poor for women. The lowest mean squared prediction errors (MSPRs) were given by Henry equations in men and Cole equations in women. Henry and Cole equations gave lower values than Schofield equations, except for men over 60 years of age. Henry equations were the most accurate in men. None of the three equations performed consistently better in women.

Conclusion

These results support the use of Henry equations in men with a wide range of age and BMI. None of the proposed predictive equations seem to be appropriate to estimate BMR in women.

Day-to-day variance in measurement of resting metabolic rate using ventilated-hood and mouthpiece & nose-clip indirect calorimetry systems

BACKGROUND

To know if the magnitude of change in resting metabolic rate (RMR) observed during an intervention is meaningful, it is imperative to first identify the variability that occurs within individuals from day to day under normal conditions. The 2 most common systems used to measure RMR involve a ventilated hood or a mouthpiece & nose clip to collect expired gases. The variation in measurement using these 2 approaches has not been systematically compared.

METHODS

RMR was measured in 10 healthy adults during 5 separate testing sessions within a 2-week period where usual diet and physical activity were maintained. Each testing session consisted of one measurement of RMR using a ventilated hood system, followed by another using a mouthpiece & nose-clip system.

RESULTS

No significant difference in RMR was evident between measurement sessions using either indirect calorimeter. Oxygen consumption and RMR were significantly higher using the mouthpiece & nose-clip system. Average within-individual coefficient of variation for RMR was significantly lower for the ventilated-hood system. RMR measures were consistently lower using the ventilated-hood system by an average of 94.5 +/- 63.3 kcal. Day-to-day variance was between 2% and 4% for both systems.

CONCLUSIONS

The use of either system is appropriate for assessing RMR in clinical and research settings, but alternating between systems should be undertaken with caution. A change in RMR must be greater than approximately 6% (96 kcal/d; 1.2 kcal/kg/d) or approximately 8% (135 kcal/d; 1.7 kcal/kg/d) when using a ventilated-hood system or a mouthpiece & nose-clip system, respectively, to observe any meaningful intervention-related differences within individuals.

Best Practice Methods to Apply to Measurement of Resting Metabolic Rate in Adults: A Systematic Review

Several factors may alter apparent resting metabolic rate (RMR) during measurement with indirect calorimetry. Likewise, numerous indirect calorimetry measurement protocols have been developed over the years, and the methodology employed could influence test results. As part of a larger project to determine the role of indirect calorimetry in clinical practice, a systematic review of the literature was undertaken to determine the ideal subject condition and test methodology for obtaining reliable measurement of RMR with indirect calorimetry. Food, ethanol, caffeine, and nicotine affect RMR for a variable number of hours after consumption; therefore, intake of these items must be controlled before measurement. Activities of daily living increase metabolic rate, but a short rest (< or =20 minutes) before testing is sufficient for the effect to dissipate. Moderate or vigorous physical activity has a longer carryover effect and therefore must be controlled in the hours before a measurement of RMR is attempted. Limited data were found regarding ideal ambient conditions for RMR testing. Measurement duration of 10 minutes with the first 5 minutes deleted and the remaining 5 minutes having a coefficient of variation <10% gave accurate readings of RMR. Individuals preparing for RMR measurement via indirect calorimetry should refrain from eating, consuming ethanol and nicotine, smoking, and engaging in physical activity for varying times before measurement. The test site should be physically comfortable and the individual should have 10 to 20 minutes to rest before measurement commences. A 10-minute test duration with the first 5 minutes discarded and the remaining 5 minutes having a coefficient of variation of <10% will give an accurate measure of RMR.

Reducing the time period of steady state does not affect the accuracy of energy expenditure measurements by indirect calorimetry

Achievement of steady state during indirect calorimetry measurements of resting energy expenditure (REE) is necessary to reduce error and ensure accuracy in the measurement. Steady state is often defined as 5 consecutive min (5-min SS) during which oxygen consumption and carbon dioxide production vary by ±10%. These criteria, however, are stringent and often difficult to satisfy. This study aimed to assess whether reducing the time period for steady state (4-min SS or 3-min SS) produced measurements of REE that were significantly different from 5-min SS. REE was measured with the use of open-circuit indirect calorimetry in 39 subjects, of whom only 21 (54%) met the 5-min SS criteria. In these 21 subjects, median biases in REE between 5-min SS and 4-min SS and between 5-min SS and 3-min SS were 0.1 and 0.01%, respectively. For individuals, 4-min SS measured REE within a clinically acceptable range of ±2% of 5-min SS, whereas 3-min SS measured REE within a range of −2–3% of 5-min SS. Harris-Benedict prediction equations estimated REE for individuals within ±20–30% of 5-min SS. Reducing the time period of steady state to 4 min produced measurements of REE for individuals that were within clinically acceptable, predetermined limits. The limits of agreement for 3-min SS fell outside the predefined limits of ±2%; however, both 4-min SS and 3-min SS criteria greatly increased the proportion of subjects who satisfied steady state within smaller limits than would be achieved if relying on prediction equations.

Participant characteristics associated with errors in self-reported energy intake from the Women's Health Initiative food-frequency questionnaire

BACKGROUND

Errors in self-reported dietary intake threaten inferences from studies relying on instruments such as food-frequency questionnaires (FFQs), food records, and food recalls.

OBJECTIVE

The objective was to quantify the magnitude, direction, and predictors of errors associated with energy intakes estimated from the Women's Health Initiative FFQ.

DESIGN

Postmenopausal women (n = 102) provided data on sociodemographic and psychosocial characteristics that relate to errors in self-reported energy intake. Energy intake was objectively estimated as total energy expenditure, physical activity expenditure, and the thermic effect of food (10% addition to other components of total energy expenditure).

RESULTS

Participants underreported energy intake on the FFQ by 20.8%; this error trended upward with younger age (P = 0.07) and social desirability (P = 0.09) but was not associated with body mass index (P = 0.95). The correlation coefficient between reported energy intake and total energy expenditure was 0.24; correlations were higher among women with less education, higher body mass index, and greater fat-free mass, social desirability, and dissatisfaction with perceived body size (all P < 0.10).

CONCLUSIONS

Energy intake is generally underreported, and both the magnitude of the error and the association of the self-reporting with objectively estimated intake appear to vary by participant characteristics. Studies relying on self-reported intake should include objective measures of energy expenditure in a subset of participants to identify person-specific bias within the study population for the dietary self-reporting tool; these data should be used to calibrate the self-reported data as an integral aspect of diet and disease association studies.