Assessing validity and reliability of resting metabolic rate in six gas analysis systems

Energy intake and energy expenditure are minimally impacted by acute cold exposure in individuals living with obesity

CONTEXT

Cold exposure (CE) has been purported to be a possible weight loss strategy and to be anorexigenic, however, the impacts of CE on appetite and energy intake have not been fully explored, more so in individuals living with obesity.

OBJECTIVE

Determine the effects of a single dose of moderate CE on energy expenditure, intake, and appetite regulation in individuals living with obesity.

DESIGN

Forty-seven individuals living with obesity (18 males) underwent two experimental sessions, one 90-min CE (10 °C fluid using a liquid conditioned suit) and one control. Energy expenditure (indirect calorimetry), energy intake (food menu), subjective appetite (Visual analogue scales), food reward (Leeds Food Preference Questionnaire), appetite-related peptides (ELISA), skin temperature (Thermocouples), thermal comfort and thermal sensation (Likert scales) were assessed.

RESULTS

CE produced a small (18%) but significant increase in energy expenditure over 90 min (p < 0.001). Energy intake during lunch increased slightly (10%), yet significantly following CE (p = 0.008) before decreasing for the remainder of the day (p = 0.049). There were no differences in subjective appetite (p > 0.05), but there was a decrease in the rewarding value of low-fat sweet foods (p < 0.05). Leptin concentrations decreased significantly (p = 0.004), whereas GLP-1 concentrations were increased (p = 0.003) in response to CE. Thermal comfort and sensation also both decreased significantly during exposure (p < 0.001).

CONCLUSION

Although both energy expenditure and intake significantly changed, CE caused minimal impacts to energy balance in individuals living with obesity. When combined with the high levels of discomfort, these results question the efficiency of CE as an intervention able to produce meaningful changes in body weight and composition in individuals living with obesity.

Methods for estimating resting energy expenditure in intensive care patients: A comparative study of predictive equations with machine learning and deep learning approaches

BACKGROUND

Accurate estimation of resting energy expenditure (REE) is critical for guiding nutritional therapy in critically ill patients. While indirect calorimetry (IC) is the gold standard for REE measurement, it is not routinely feasible in clinical settings due to its complexity and cost. Predictive equations (PEs) offer a simpler alternative but are often inaccurate in critically ill populations. While recent advancements in machine learning (ML) and deep learning (DL) offer potential for improving REE estimation by capturing complex relationships between physiological variables, these approaches have not yet been widely applied or validated in critically ill populations.

METHODOLOGY

This prospective study compared the performance of nine commonly used PEs, including the Harris-Benedict (H-B1919), Penn State, and TAH equations, with ML models (XGBoost, Random Forest Regressor [RFR], Support Vector Regression), and DL models (Convolutional Neural Networks [CNN]) in estimating REE in critically ill patients. A dataset of 300 IC measurements from an intensive care unit (ICU) was used, with REE measured by both IC and PEs. The ML/DL models were trained using a combination of static (i.e., age, height, body weight) and dynamic (i.e., minute ventilation, body temperature) variables. A five-fold cross validation was performed to assess the model prediction performance using the root mean square error (RMSE) metric.

RESULTS

Of the PEs analysed, H-B1919 yielded the lowest RMSE at 362 calories. However, the XGBoost and RFR models significantly outperformed all PEs, achieving RMSE values of 199 and 200 calories, respectively. The CNN model demonstrated the poorest performance among ML models, with an RMSE of 250 calories. The inclusion of additional categorical variables such as body mass index (BMI) and body temperature classes slightly reduced RMSE across ML and DL models. Despite data augmentation and imputation techniques, no significant improvements in model performance were observed.

CONCLUSION

ML models, particularly XGBoost and RFR, provide more accurate REE estimations than traditional PEs, highlighting their potential to better capture the complex, non-linear relationships between physiological variables and REE. These models offer a promising alternative for guiding nutritional therapy in clinical settings, though further validation on independent datasets and across diverse patient populations is warranted.

Precision medicine for obesity: current evidence and insights for personalization of obesity pharmacotherapy

Obesity is a chronic and complex disease associated with increased morbidity, mortality, and financial burden. It is expected that by 2030 one of two people in the United States will have obesity. The backbone for obesity management continues to be lifestyle interventions, consisting of calorie deficit diets and increased physical activity levels, however, these interventions are often insufficient to achieve sufficient and maintained weight loss. As a result, multiple patients require additional interventions such as antiobesity medications or bariatric interventions in order to achieve clinically significant weight loss and improvement or resolution of obesity-associated comorbidities. Despite the recent advances in the field of obesity pharmacotherapy that have resulted in never-before-seen weight loss outcomes, comorbidity improvement, and even reduction in cardiovascular mortality, there is still a significant interindividual variability in terms of response to antiobesity medications, with a subset of patients not achieving a clinically significant weight loss. Currently, the trial-and-error paradigm for the selection of antiobesity medications results in increased costs and risks for developing side effects, while also reduces engagement in weight management programs for patients with obesity. The implementation of a precision medicine framework to the selection of antiobesity medications might help reduce heterogeneity and optimize weight loss outcomes by identifying unique subsets of patients, or phenotypes, that have a better response to a specific intervention. The detailed study of energy balance regulation holds promise, as actionable behavioral and physiologic traits could help guide antiobesity medication selection based on previous mechanistic studies. Moreover, the rapid advances in genotyping, multi-omics, and big data analysis might hold the key to discover additional signatures or phenotypes that might respond better to a certain intervention and might permit the widespread adoption of a precision medicine approach for obesity management.

The effects of high protein intakes during energy restriction on body composition, energy metabolism and physical performance in recreational athletes

BACKGROUND

Athletes employ weight loss practices to lower body fat and maintain fat-free mass (FFM). High protein diets have been shown to produce greater fat loss and retention of lean mass during periods of energy restriction (ER) in sedentary individuals with obesity, but less is known about the effects of high protein diets in trained individuals during ER. Although current recommendations for protein intake in active individuals are 1.2-1.7 g/kg, it is unclear whether higher intakes are necessary to maximize FFM retention and maximize physical performance in athletes undergoing periods of ER.

OBJECTIVE

Determine whether high protein intakes could maximize FFM retention and physical performance in trained individuals after a period of ER.

METHODS

Twenty-one college aged athletes underwent a 6-week 25% ER + 3-day full body resistance training. Participants were randomly assigned to a low (~1.2 g/kg), moderate (~1.6 g/kg) or high (~2.2 g/kg) protein intake. Baseline and post-intervention outcomes: Dual X-ray absorptiometry, isotopic water dilution, indirect calorimetry, dietary records and strength based physical testing.

RESULTS

Significant reductions in body mass (p = 0.047) and fat mass (p = 0.04) with simultaneous increases in FFM (p = 0.037) were noted for all groups, with no protein intake effect. Significant increases in physical performance outcomes (5RM strength) were noted for most measures (p < 0.05).

CONCLUSION

Current protein intake recommendations of 1.2-1.7 g/kg appear sufficient for most athletes even during periods of ER to maintain FFM and physical performance.

Energy expenditure and slow-wave sleep in runners: Focusing on reproductive function, chronic training, and sex

This comparative study focused on chronic exercise training, menstrual cycle, menstruation, and sex related with slow-wave sleep and energy expenditure (EE) during sleep in runners and controls. Participants included 26 highly trained runners (9 males, 8 amenorrheic females, and 9 menstruating females) and 20 controls (10 males and 10 menstruating females) aged 21 ± 2 years. Sleeping metabolic rate and EE during slow-wave sleep were 2.7% and 3.9% higher in the luteal than the follicular phase for female runners. Significant interactions were found between the 8-h time course adjusted EE and menstruation, exercise training, and sex. Sleep stage durations did not differ between groups. Interestingly, amenorrheic runners did not suppress sleeping and overnight metabolic rates, suggesting that EE in sleep may not be a causative factor for amenorrhea in runners. This study highlights the complex relationship between chronic exercise, menstrual cycle, and sex on EE during sleep.

System for continuous metabolic monitoring of mechanically ventilated patients

In clinical settings, due largely to the cost, size and calibration complexity of existing indirect calorimetry systems, there is seldom instrumentation available to provide reliable, continuous tracking of a mechanically ventilated patient's metabolic output in support of proper nutrition. The atypical metabolisms associated with critically ill patients are difficult to predict and both underfeeding and overfeeding lead to negative impacts on both mortality and the recovery and healing processes. With these issues in mind, a novel ventilator-agnostic indirect calorimetry sensor design, prototype development, and validation were undertaken with the goal of enabling 24/7 metabolic monitoring of mechanically ventilated patients by means of a passive, rate-proportional side-stream sampling scheme and miniature mixing chamber. The miniature mixing chamber enables the use of small, low-cost gas concentration and flow sensing components to ensure the affordability of commercial design-for-manufacture implementations of the prototype sensor. In addition to continuous measurement of patient metabolism, the prototype sensor also enables autonomous monitoring and detection of calibration drift in the gas measurement sensors without disrupting the patient ventilation.

Validity and reliability of a new whole room indirect calorimeter to assess metabolic response to small calorie loads

We overview of our whole room indirect calorimeter (WRIC), demonstrate validity and reliability of our WRIC, and explore a novel application of Bayesian hierarchical modeling to assess responses to small carbohydrate loads. To assess WRIC validity seven gas infusion studies were performed using a gas blender and profiles designed to mimic resting and postprandial metabolic events. Sixteen participants underwent fasting and postprandial measurements, during which they consumed a 75-kcal drink containing sucrose, dextrose, or fructose in a crossover design. Linear mixed effects models were used to compare resting and postprandial metabolic rate (MR) and carbohydrate oxidation. Postprandial carbohydrate oxidation trajectories for each participant and condition were modeled using Bayesian Hierarchical Modeling. Mean total error in infusions were 1.27 ± 0.67% and 0.42 ± 0.70% for VO2 and VCO2 respectively, indicating a high level of validity. Mean resting MR was similar across conditions ([Formula: see text] = 1.05 ± 0.03 kcal/min, p = 0.82, ICC: 0.91). While MR increased similarly among all conditions (~13%, p = 0.29), postprandial carbohydrate oxidation parameters were significantly lower for dextrose compared with sucrose or fructose. We provide evidence validating our WRIC and a novel application of statistical methods useful for research using WRIC.

Evaluating Airflow Sensor Methods: Precision in Indirect Calorimetry

This study assesses the impact of three volumetric gas flow measurement methods-turbine (fT); pneumotachograph (fP), and Venturi (fV)-on predictive accuracy and precision of expired gas analysis indirect calorimetry (EGAIC) across varying exercise intensities. Six males (Age: 38 ± 8 year; Height: 178.8 ± 4.2 cm;V ̇ O 2 peak $$ \dot{V}{\mathrm{O}}_2\mathrm{peak} $$ : 42 ± 2.8 mL O2 kg-1 min-1) and 14 females (Age = 44.6 ± 9.6 year; Height = 164.6 ± 6.9 cm;V ̇ O 2 peak $$ \dot{V}{\mathrm{O}}_2\mathrm{peak} $$ = 45 ± 8.6 mL O2 kg-1 min-1) were recruited. Participants completed physical exertion on a stationary cycle ergometer for simultaneous pulmonary minute ventilation (V ̇ $$ \dot{V} $$ ) measurements and EGAIC computations. Exercise protocols and subsequent conditions involved a 5-min cycling warm-up at 25 W min-1, incremental exercise to exhaustion (V ̇ O 2 $$ \dot{V}{\mathrm{O}}_2 $$ ramp test), then a steady-state exercise bout induced by a constant Watt load equivalent to 80% ventilatory threshold (80% VT). A linear mixed model revealed that exercise intensity significantly affectedV ̇ O 2 $$ \dot{V}{\mathrm{O}}_2 $$ measurements (p < 0.0001), whereas airflow sensor method (p = 0.97) and its interaction with exercise intensity (p = 0.91) did not. Group analysis of precision yielded aV ̇ O 2 $$ \dot{V}{\mathrm{O}}_2 $$ CV % = 21%; SEM = 5 mL O2 kg-1 min-1. Intra- and interindividual analysis of precision via Bland-Altman revealed a 95% confidence interval (CI) precision benchmark of 3-5 mL kg-1 min-1. Agreement among methods decreased at power outputs elicitingV ̇ $$ \dot{V} $$ up to 150 L min-1, indicating a decrease in precision and highlighting potential challenges in interpreting biological variability, training response heterogeneity, and test-retest comparisons. These findings suggest careful consideration of airflow sensor method variance across metabolic cart configurations.

Eight weeks of daily cottonseed oil intake attenuates postprandial angiopoietin-like proteins 3 and 4 responses compared to olive oil in adults with hypercholesterolemia: A secondary analysis of a randomized clinical trial

Angiopoietin-like proteins (ANGPTLs) -3, -4, and -8 are regulators of lipid metabolism and have been shown to respond to changes in dietary fats. It is unknown how ANGPTLs respond to cottonseed oil (CSO) and olive oil (OO) consumption in a population with hypercholesterolemia. The purpose of this study was to determine the impact of CSO vs. OO consumption on fasting and postprandial ANGPTL responses in adults with hypercholesterolemia. We hypothesized that CSO would have lower fasting and postprandial ANGPTL responses compared with OO. Forty-two adults with high cholesterol completed a single-blind, randomized trial comparing CSO (n = 21) vs. OO (n = 21) diet enrichment. An 8-week partial outpatient feeding intervention provided ∼60% of the volunteers' total energy expenditure (∼30% of total energy expenditure as CSO or OO). The remaining 40% was not controlled. Fasting blood draws were taken at pre-, mid-, and postintervention visits. Volunteers consumed a high saturated fat meal followed by 5 hours of blood draws pre- and postvisits. Fasting ANGPTL3 had a marginally significant treatment by visit interaction (P = .06) showing an increase from pre- to postintervention in CSO vs. OO (CSO: 385.1 ± 27.7 to 440.3 ± 33.9 ng/mL; OO: 468.2 ± 38.3 to 449.2 ± 49.5 ng/mL). Both postprandial ANGPTL3 (P = .02) and ANGPTL4 (P < .01) had treatment by visit interactions suggesting increases from pre- to postintervention in OO vs. CSO with no differences between groups in ANGPTL8. These data show a worsening (increase) of postprandial ANGPTLs after the OO, but not CSO, intervention. This aligns with previously reported data in which postprandial triglycerides were protected from increases compared with OO. ANGPTLs may mediate protective effects of CSO consumption on lipid control. This trial was registered at clinicaltrials.gov (NCT04397055).

Resting energy metabolism and sweet taste preference during the menstrual cycle in healthy women

Differences in blood concentration of sex hormones in the follicular (FP) and luteal (LP) phases may influence energy metabolism in women. We compared fasting energy metabolism and sweet taste preference on a representative day of the FP and LP in twenty healthy women (25·3 (sd 5·1) years, BMI: 22·2 (sd 2·2) kg/m2) with regular self-reported menses and without the use of hormonal contraceptives. From the self-reported duration of the three prior menstrual cycles, the predicted FP and LP visits were scheduled for days 5-12 and 20-25 after menses, respectively. The order of the FP and LP visits was randomly assigned. On each visit, RMR and RQ by indirect calorimetry, sweet taste preference by the Monell two-series forced-choice tracking procedure, serum fibroblast growth factor 21 by a commercial ELISA (FGF21, a liver-derived protein with action in energy balance, fuel oxidation and sugar preference) and dietary food intake by a 24-h dietary recall were determined. Serum progesterone and oestradiol concentrations displayed the expected differences between phases. RMR was lower in the FP v. LP (5042 (sd 460) v. 5197 (sd 490) kJ/d, respectively; P = 0·04; Cohen effect size, d rm = 0·33), while RQ showed borderline significant higher values (0·84 (sd 0·05) v. 0·81 (sd 0·05), respectively; P = 0·07; d rm = 0·62). Also, in the FP v. LP, sweet taste preference was lower (12 (sd 8) v. 16 (sd 9) %; P = 0·04; d rm = 0·47) concomitant with higher serum FGF21 concentration (294 (sd 164) v. 197 (sd 104) pg/ml; P < 0·01; d rm = 0·66). The menstrual cycle is associated with changes in energy expenditure, sweet taste preference and oxidative fuel partitioning.

No Observed Difference in Inflammatory and Coagulation Markers Following Diets Rich in n-6 Polyunsaturated Fat vs Monounsaturated Fat in Adults With Untreated Hypercholesterolemia: A Randomized Trial

BACKGROUND

Inflammatory and prothrombotic responses are hallmark to the progression of cardiovascular disease and may be influenced by the type of dietary fat. Cottonseed oil (CSO) is rich in n-6 polyunsaturated fats and improves traditional cardiovascular disease risk factors such as cholesterol profiles. However, some clinicians are still hesitant to promote n-6 polyunsaturated fats consumption despite growing evidence suggesting they may not be independently pro-inflammatory.

OBJECTIVE

To investigate the inflammatory and coagulation marker responses to an 8-week diet intervention rich in either CSO or olive oil (OO) (OO is rich in monounsaturated fat) in adults with untreated hypercholesterolemia.

DESIGN

This was a secondary analysis of a parallel-arm randomized clinical trial with the main outcome of cholesterol measures.

PARTICIPANTS/SETTING

Participants included in this analysis were 42 sedentary adults aged 30 to 75 years (62% women) in the Athens, GA, area, between May 2018 and June 2021, with untreated hypercholesterolemia or elevated blood lipids and body mass index >18.5. Hypercholesterolemia was defined as at least two blood lipid levels in a borderline undesirable/at risk range (total cholesterol level ≥180 mg/dL, low-density lipoprotein cholesterol level ≥110 mg/dL, high-density lipoprotein cholesterol level <50 mg/dL, or triglyceride level ≥130 mg/dL), or at least one in an undesirable range (total cholesterol level ≥240 mg/dL, low-density lipoprotein cholesterol level ≥160 mg/dL, high-density lipoprotein cholesterol level <40 mg/dL, or triglyceride level ≥200 mg/dL).

INTERVENTION

Participants were randomly assigned to either the CSO or OO group in a partial outpatient feeding trial. Meals from the study provided approximately 60% of their energy needs with 30% of energy needs from either CSO or OO for 8 weeks. Participants fulfilled their remaining energy needs with meals of their choosing.

MAIN OUTCOME MEASURES

Fasting plasma concentrations of inflammatory markers, including C-reactive protein, tumor necrosis factor-α, interleukin-6, and interleukin-1β were measured at baseline and 8 weeks. Markers of coagulation potential, including plasminogen activator inhibitor-1, and tissue factor were measured at the same time points.

STATISTICAL ANALYSES PERFORMED

Repeated measures linear mixed models were used with treatment and visit in the model for analyses of all biochemical markers.

RESULTS

There were no significant differences in fasting C-reactive protein (P = 0.70), tumor necrosis factor-α (P = 0.98), interleukin-6 (P = 0.21), interleukin-1β (P = 0.13), plasminogen activator inhibitor-1 (P = 0.29), or tissue factor (P = 0.29) between groups across the intervention.

CONCLUSIONS

Inflammation and coagulation marker responses to diets rich in CSO vs OO were not significantly different between groups, and neither group showed changes in these markers in adults with untreated hypercholesterolemia. This provides additional evidence suggesting that dietary n-6 polyunsaturated fats may not promote inflammation compared with monounsaturated fatty acids, even in adults at increased risk for cardiovascular disease.

Body composition and resting energy expenditure in a group of children with achondroplasia

BACKGROUND

Persons with achondroplasia develop early obesity, which is a comorbidity associated with other complications. Currently, there are no validated specific predictive equations to estimate resting energy expenditure in achondroplasia.

METHODS

We analyzed the influence of body composition on this parameter and determined whether predictive models used for children with standard height are adjusted to achondroplasia. In this cross-sectional study, we measured anthropometric parameters in children with achondroplasia. Fat mass was obtained using the Slaughter skinfold-thickness equation and resting energy expenditure was determined with a Fitmate-Cosmed calorimeter and with predictive models validated for children with average height (Schofield, Institute of Medicine, and Tverskaya).

RESULTS

All of the equations yielded a lower mean value than resting energy expenditure with indirect calorimetry (1256±200 kcal/day [mean±SD]) but the closest was the Tverskaya equation (1017 ± 64 kcal/day), although the difference remained statistically significant. We conclude that weight and height have the greatest influence on resting energy expenditure.

CONCLUSION

We recommend studying the relationship between body composition and energy expenditure in achondroplasia in more depth. In the absence of valid predictive models suitable for clinical use to estimate body composition and resting energy expenditure in achondroplasia, it is recommended to use the gold standard methods by taking into account certain anthropometric parameters.

Resting energy expenditure changes after antineoplastic treatment in gynecological cancer: a prospective pilot study

Introduction

Introduction: energy metabolism in cancer patients is influenced by different factors. However, the effect of antineoplastic treatment is not clear, especially in women. Objective: to evaluate resting energy expenditure (REE) by indirect calorimetry (IC) before (T0) and after (T1) first cycle period of antineoplastic therapy: radiotherapy (RT), chemotherapy (CT), and concomitant chemoradiation therapy (CRT), quality of life (QoL) and accuracy of REE were compared with international guidelines recommendations per kilogram (European Society for Clinical Nutrition and Metabolism [ESPEN]). Methods: an observational, longitudinal study was conducted in women with gynecological cancer diagnosis undergoing antineoplastic treatment: RT, CT and CRT. Weight loss, actual body weight and height were measured. REE was evaluated in T0-T1 and compared with ESPEN recommendations. Kruskal-Wallis test and Bland-Alman analysis were used to determine the agreement (± 10 % of energy predicted) of REE adjusted by physical activity (TEE) compared with ESPEN recommendations, respectively. Results: fifty-four women with cancer were included: 31.5 % (n = 17) for RT group, 31.5 % (n = 17) for CT group and 37 % (n = 20) for CRT group. REE showed statistical differences between T0 and T1 in the total population (p = 0.018), but these were not associated with anticancer therapy groups (p > 0.05). QoL had no significant changes after treatment (p > 0.05). Accuracy of 25 and 30 kcal/kg compared to TEE was less than 30 %. Conclusion: REE in women with gynecological cancer decreased after antineoplastic treatments but this is not associated with a particular antineoplastic therapy. It is needed to develop research to determine the accuracy of ESPEN recommendations with TEE estimated by IC and clinical factors in women with cancer.

Resting metabolic rate in healthy Singaporeans: Performance of the Harris-Benedict equation and a new predictive model

Background

Prediction equations for resting metabolic rate (RMR) are valuable in managing patients’ weight; however, no accurate equation exists for Singaporeans.

Objective

To develop and cross-validate a predictive regression equation for RMR in Singaporeans, using indirect calorimetry as the reference method.

Methods

104 healthy Singaporeans (34.3 ± 12.2 years) participated, comprising 34 men and 70 women. Anthropometric measurements and demographics information were obtained from participants. RMR was measured via indirect calorimetry (TrueOne 2400 system). Stepwise regression analysis was used to develop the most parsimonious predictive equation. Performance of the equation was evaluated using ordinary least products (OLP) regression and Bland–Altman analysis, whilst internal cross-validation was performed by use of the predicted residual sum of squares (PRESS) method. To compare the new equation with existing ones, the performance of the Harris-Benedict equation was also evaluated.

Results

The best predictive equation takes the form RMR(kcal) = 918 + 16.5(weight)-135.7(gender) - 1152(Waist-to-height-ratio) +0.014(International Physical Activity Questionnaire Score), where gender = 1 (female) or 0 (male). OLP regression revealed no systematic bias for the new equation. Bland–Altman analysis showed that its total (systematic and random) error was 212 kcal. Internal model validation using the PRESS method revealed minimal reduction in predictive accuracy. In contrast, OLP regression showed a significant pattern of over-prediction by the Harris-Benedict equation (y-intercept = −280 kcal; 95%CI, −100 to −461 kcal).

Conclusions

Our new equation outperformed the Harris-Benedict equation in accurately predicting RMR in Singaporeans. Comprising easily obtained anthropometric and self-reported measures, we envisage its potential relevance in clinical and epidemiological settings.

Validity and reliability of a new whole room indirect calorimeter to assess metabolic response to small-calorie loads

Objective

To provide an overview of our whole room indirect calorimeter (WRIC), demonstrate validity and reliability of our WRIC, and explore a novel application of Bayesian hierarchical modeling to assess responses to small carbohydrate loads.

Methods

Seven gas infusion studies were performed using a gas blender and profiles designed to mimic resting and postprandial metabolic events to assess WRIC validity. In a crossover design, 16 participants underwent fasting and postprandial measurements, during which they consumed a 75-kcal drink containing sucrose, dextrose, or fructose. Linear mixed effects models were used to compare resting and postprandial metabolic rate (MR) and CO (CO). Bayesian Hierarchical Modeling was also used to model postprandial CO trajectories for each participant and condition.

Results

Mean total error in infusions were 1.27 ± 1.16% and 0.42 ± 1.21% for VO2 and VCO2 respectively, indicating a high level of validity. Mean resting MR was similar across conditions (x ¯ = 1.05 ± 0.03   kcal / min , p=0.82, ICC: 0.91). While MR increased similarly among all conditions (~13%, p=0.29), postprandial CO parameters were significantly lower for dextrose compared with sucrose or fructose.

Conclusions

Our WRIC validation and novel application of statistical methods presented here provide important foundations for new research directions using WRIC.

High resting energy expenditure, less fat-free mass, and less muscle strength in HIV-infected children: a matched, cross-sectional study

Background and aims

Many improvements have been made in the treatment of human immunodeficiency virus (HIV) in pediatric patients; however, challenges remain in terms of achieving normal growth, body composition, and metabolism during treatment, etc. Current nutritional recommendations are based on studies performed in adults, with limited data on the HIV-infected pediatric population. Therefore, this study aimed to compare the resting energy expenditure (REE) of asymptomatic HIV-infected pediatric patients with healthy counterparts and to compare body composition, dietary intake, and physical activity between the two groups.

Methods

This was a cross-sectional study of asymptomatic HIV-infected children who were receiving antiretroviral therapy; the infected group was compared with the uninfected group, matched by age (± 6 months), sex, and body mass index (± 0.5 z-score). Participants were recruited between 2021 and 2022, as outpatients. In both groups, REE was determined by indirect calorimetry and body composition by bioelectrical impedance analysis and hand strength, measured using a hydraulic hand dynamometer.

Results

Seventy-eight participants were enrolled, where n = 39 HIV-infected children and n = 39 controls, with a mean age of 11.6 ± 3.4 years old. REE was significantly higher in the HIV group (1254.4 ± 334.7 kcal/day vs. 1124.7 ± 321 kcal/day, p = 0.013) than in the control group. Fat-free mass (FFM) was lower in the HIV group (28.2 ± 10.5 kg vs. 32 ± 11.2 kg, p = 0.001); this trend continued when the index skeletal muscle was evaluated (7.2 ± 1.2 vs. 7.6 ± 1.5, p = 0.04). The strength of the dominant hand was also lower in the HIV group (12 (8-18) kg vs. 20 (10.5-26) kg, p < 0.0001).

Conclusions

Children with asymptomatic HIV infection have higher REE than their uninfected peers. They also present decreased FFM, skeletal muscle mass index, and muscle strength. These parameters should be considered during nutritional assessment in this population to have a favorable impact on nutritional status and growth.

A single bout of breast milk expression does not increase resting metabolic rate

INTRODUCTION

Breastfeeding women have elevated resting metabolic rate (RMR); however, whether a single bout of lactation increases RMR is unknown. This study aimed to determine if a single bout of lactation acutely increased RMR.

METHODS

Twenty-two lactating women (age: 31 ± 0.9 year, body mass index: 27.3 ± 1.2 kg/m2 ) were recruited. RMR was assessed at baseline and at 1- and 2-h following breast milk expression.

RESULTS

RMR was unchanged in lactating women following a single bout of lactation (baseline: 1437 ± 39; 1 h: 1425 ± 37 2 h: 1440 ± 31 kcal/day) (p > .05). RMR was not correlated to daily milk produced (r = 0.05, p > .05), but was correlated to body mass (r = 0.74, p < .001), fat-free mass (kg) (r = 0.61, p < .01), and fat mass (kg) (r = 0.71, p < .01).

CONCLUSION

RMR in lactating women appears to be more related to body mass or composition in the postpartum period rather than lactation.

Reliability of resting metabolic rate between and within day measurements using the Vyntus CPX system and comparison against predictive formulas

Background: To detect longitudinal changes of resting metabolic rate (RMR) resulting from the effects of energetic stress, reliable RMR measurements are crucial. The Vyntus CPX is a new automated indirect calorimetry system for which RMR reliability has not been determined. Additionally, its agreement with common predictive RMR formulas is unknown. Aim: To determine the within and between-day reliability of RMR measurements using the Vyntus CPX system and its agreement with predictive RMR formulas. Methods: Young (31  ±  7 years) healthy participants (n = 26, 12 females, 14 males) completed three measurements of RMR, two consecutive measures on the same day, one the day before/after, all under standardised conditions. Reliability was assessed with pairwise comparisons of between-day at the same time (BDST), within day consecutive measurements (WDCM) and between-day different time (BDDT), for parameters of reliability (mean change (MC), intraclass correlation (ICC) and typical error of measurement (TEM)). Measured RMR values (kcal/day) were compared against predictive values of 4 common formulas. Results: Parameters of reliability (mean, (95% confidence interval)) were: -BDST: MC, 0.2(-2.3-2.7)% (p = 0.67); ICC, 0.92(0.84-0.97); TEM, 4.5(3.5-6.2)%. -WDCM: MC, -2.5(-6.2-1.3)% (p = 0.21); ICC, 0.88(0.74-0.88); TEM, 7.0(5.4-9.8)%. -BDDT: MC, -1.5(-4.8-1.9)% (p = 0.57); ICC, 0.90(0.76-0.95); TEM, 6.1(4.8-8.5)%. RMR_ratios (measured/predicted) were: 1.04  ±  0.14 (Nelson, p = 0.13), 1.03  ±  0.10 (Mifflin, p = 0.21), 0.98  ±  0.09 (Harris-benedict, p = 0.30), 0.95  ±  0.11 (Cunningham₁₉₈₀, p = 0.01), 1.00  ±  0.12 (Cunningham₁₉₉₁, p = 0.90) and 0.96  ±  0.13 (DXA, p = 0.03). Conclusions: The Vyntus CPX is reliable and measured RMR values agreed with four predictive formulas but are lower than Cunningham₁₉₈₀ and DXA RMR estimates for this population.

Hunger and satiety responses to diets enriched with cottonseed oil vs. olive oil

Studies suggest that the type of dietary fat consumed habitually may modulate appetite and further influence weight management. The purpose of this study was to evaluate the impact of an 8-week diet intervention enriched with either cottonseed oil (CSO; polyunsaturated fat-rich) or olive oil (OO; monounsaturated fat-rich) on appetite responses in adults with high cholesterol. This was a parallel design, randomized partial outpatient feeding trial designed to provide approximately 60% of participants daily energy needs with ∼30% of energy needs as CSO (n = 21, BMI 27.3 ± 0.92 kg/m², age 53 ± 2y) or OO (n = 21, BMI 27.6 ± 1.20 kg/m², age 54 ± 2y). A high saturated fat meal challenge was completed at pre- and post-intervention visits with 5 h postprandial blood draws and visual analog scales (VAS) for cholecystokinin (CCK), peptide YY (PYY), ghrelin, and subjective appetite, respectively. Participants also completed VAS questionnaires hourly and recorded dietary intake after leaving the lab for the remainder of the day. There was a greater increase in fasting CCK (CSO: 0.54 ± 0.03 to 0.56 ± 0.04; OO: 0.63 ± 0.07 to 0.60 ± 0.06 ng/ml p = 0.05), a greater suppression of postprandial ghrelin (p < 0.01), and a greater increase in postprandial VAS fullness (p = 0.04) in CSO compared to OO. Additionally, there was a greater decrease in self-reported energy intake in CSO compared to OO (CSO: 2464 ± 123 to 2115 ± 123; OO: 2263 ± 147 to 2,434 ± 184 kcal/d p = 0.02). Only postprandial VAS prospective consumption showed greater suppression (p = 0.03) in OO vs. CSO. Altogether, these data show that CSO has a greater effect on appetite suppression than OO diet enrichment and may be beneficial for weight maintenance, especially in a population at-risk for chronic disease. Registered at clinicaltrials.gov: NCT04397055.

Reproducibility of the energy metabolism response to an oral glucose tolerance test: influence of a postcalorimetric correction procedure

PURPOSE

Metabolic flexibility (MetF), which is a surrogate of metabolic health, can be assessed by the change in the respiratory exchange ratio (RER) in response to an oral glucose tolerance test (OGTT). We aimed to determine the day-to-day reproducibility of the energy expenditure (EE) and RER response to an OGTT, and whether a simulation-based postcalorimetric correction of metabolic cart readouts improves day-to-day reproducibility.

METHODS

The EE was assessed (12 young adults, 6 women, 27 ± 2 years old) using an Omnical metabolic cart (Maastricht Instruments, Maastricht, The Netherlands) after an overnight fast (12 h) and after a 75-g oral glucose dose on 2 separate days (48 h). On both days, we assessed EE in 7 periods (one 30-min baseline and six 15-min postprandial). The ICcE was performed immediately after each recording period, and capillary glucose concentration (using a digital glucometer) was determined.

RESULTS

We observed a high day-to-day reproducibility for the assessed RER (coefficients of variation [CV] < 4%) and EE (CVs < 9%) in the 7 different periods. In contrast, the RER and EE areas under the curve showed a low day-to-day reproducibility (CV = 22% and 56%, respectively). Contrary to our expectations, the postcalorimetric correction procedure did not influence the day-to-day reproducibility of the energy metabolism response, possibly because the Omnical's accuracy was ~ 100%.

CONCLUSION

Our study demonstrates that the energy metabolism response to an OGTT is poorly reproducible (CVs > 20%) even using a very accurate metabolic cart. Furthermore, the postcalorimetric correction procedure did not influence the day-to-day reproducibility. Trial registration NCT04320433; March 25, 2020.

Metabolic Responses to Eight Weeks of Consuming Cottonseed Oil v. Olive Oil in Adults with Dyslipidemia, a Randomized Trial

BACKGROUND

Differences in metabolic responses between diets rich in monounsaturated (MUFA) and polyunsaturated fats (PUFA) could affect energy balance and weight maintenance. The present study was a secondary analysis to investigate 8-week diet interventions rich in either PUFA (cottonseed oil (CSO)) or MUFA (olive oil (OO)) on metabolic responses in adults with dyslipidemia.

METHODS

Forty-one adults with dyslipidemia completed this randomized trial consisting of an 8-week partial-outpatient feeding trial. Provided foods accounted for ~60% of their daily energy needs, with ~30% of energy needs provided by CSO (n=20) or OO (n=21). At pre- and post-diet intervention visits, participants consumed a high saturated fat (SFA) meal (35% daily energy needs, 47.9% from SFA), and fasting and 3.5h postprandial indirect calorimetry was used to measure energy expenditure (EE) and substrate oxidation.

RESULTS

No changes were observed in fasting measures. The OO group had greater increases in postprandial EE (p=0.002); however, there were no differences in substrate oxidation between groups. A lack of metabolic flexibility was found in both groups, which was partially explained by changes in insulin sensitivity (homeostasis model assessment of insulin resistance (HOMA-IR)).

CONCLUSIONS

The results of the present study show OO, but not CSO, diet enrichment improves EE following the occasional high SFA meal, which may improve weight maintenance over time. Registered at clinicaltrials.gov (NCT04397055). This article is protected by copyright. All rights reserved.

Angiopoietin-Like Protein Responses to Pecan-Enriched Diets Versus a Nut-Excluded Diet

Daily pecan consumption improves fasting and postprandial triglycerides, but its effect on angiopoietin-like proteins (ANGPTLs) is unknown. The objective of this study was to investigate the impact of daily pecan consumption for 8 weeks on fasting and postprandial ANGPTL3, -8, and -4. This was an 8-week, randomized, controlled trial with three treatments: two pecan groups and a nut-free control group (n = 16). The ADD group (n = 15) consumed pecans (68 g) as part of a free-living diet, and the SUB group (n = 16) substituted the pecans (68 g) for isocaloric foods from their habitual diet. Fifty-six participants were randomized but nine subjects did not begin or finish the 8-week intervention and/or testing visits. At pre- and post-intervention, a high saturated fat meal was consumed with 3.5 h postprandial blood draws to determine changes in ANGPTL3, -8, and -4. There was a significant suppression in postprandial ANGPTL3 from pre- to post-intervention within ADD and SUB (P = .004 and P = .002, respectively) but not control (ns). There were no other changes within or between groups for fasting and postprandial outcomes. Daily pecan consumption improved postprandial ANGPTL3, which may mediate improvements in lipid metabolism.

The Impact of the Metabolic Syndrome and Its Components on Resting Energy Expenditure

We determined whether metabolic syndrome (MetS) and the increasing number of its components influenced the resting energy expenditure (REE). Data on adult men (n = 72, 40%) and women (n = 108, 60%) from European (n = 154, 86%) and Sub-Saharan African (n = 26, 14%) ancestry were used. Ninety-five (53%) participants had MetS (MetS+), while 85 (47%) were without MetS (MetS−). REE was determined through indirect calorimetry, body composition by DEXA, and clinical biochemistry by standard laboratory techniques. MetS+ had a significantly higher REE (mean ± se: MetS+: 5995 ± 87.3 vs. MetS−: 5760 ± 86.3 kJ/d, p = 0.025) when adjusted for age, gender, fat mass (FM), fat-free mass (FFM), ethnicity, season, 25OHD, insulin sensitivity, and time of data collection. Within each MetS status group, an increase in the number of components (C) resulted in a stepwise increase in REE. Relative to zero components, those with 1C had adjusted REE higher by +526 ± 248.1 kJ/d (p = 0.037), while 2C were higher than 1C by +298 ± 140.8 kJ/d (p = 0.037). Similarly, relative to 3C, those with 4C had REE higher by +242 ± 120.7 kJ/d (p = 0.049). The higher REE of 5C over 4C by 132 ± 174.5 kJ/d did not achieve statistical significance. MetS was associated with a significantly higher REE. This greater energetic cost varied directly with the numbers of its components but was most evident in those not diagnosed with the syndrome.

Predictive Equation to Estimate Resting Metabolic Rate in Older Chilean Women

Resting metabolic rate (RMR) depends on body fat-free mass (FFM) and fat mass (FM), whereas abdominal fat distribution is an aspect that has yet to be adequately studied. The objective of the present study was to analyze the influence of waist circumference (WC) in predicting RMR and propose a specific estimation equation for older Chilean women. This is an analytical cross-sectional study with a sample of 45 women between the ages of 60 and 85 years. Weight, height, body mass index (BMI), and WC were evaluated. RMR was measured by indirect calorimetry (IC) and %FM using the Siri equation. Adequacy (90% to 110%), overestimation (>110%), and underestimation (<90%) of the FAO/WHO/UNU, Harris−Benedict, Mifflin-St Jeor, and Carrasco equations, as well as those of the proposed equation, were evaluated in relation to RMR as measured by IC. Normal distribution was determined according to the Shapiro−Wilk test. The relationship of body composition and WC with RMR IC was analyzed by multiple linear regression analysis. The RMR IC was 1083.6 ± 171.9 kcal/day, which was significantly and positively correlated with FFM, body weight, WC, and FM and inversely correlated with age (p < 0.001). Among the investigated equations, our proposed equation showed the best adequacy and lowest overestimation. The predictive formulae that consider WC improve RMR prediction, thus preventing overestimation in older women.

Predictive equations for energy expenditure in adult humans: From resting to free-living conditions

Humans acquire energy from the environment for survival. A central question for nutritional sciences is how much energy is required to sustain cellular work while maintaining an adequate body mass. Because human energy balance is not exempt from thermodynamic principles, the energy requirement can be approached from the energy expenditure. Conceptual and technological advances have allowed understanding of the physiological determinants of energy expenditure. Body mass, sex, and age are the main factors determining energy expenditure. These factors constitute the basis for predictive equations for resting (REE) and total (TEE) energy expenditure in healthy adults. These equations yield predictions that differ up to ~400 kcal/d for REE and ~550 kcal/d for TEE. Identifying additional factors accounting for such variability and the most valid equations appears relevant. This review used novel approaches based on mathematical modeling of REE and analyses of the data from which REE predictive equations were generated. As for TEE, R² and SE were considered because only a few predictive equations are available. From these analyses, Oxford's and Plucker's equations appear valid for predicting REE and TEE in adults, respectively.

Blood Lipid Responses to Diets Enriched with Cottonseed Oil Compared With Olive Oil in Adults with High Cholesterol in a Randomized Trial

BACKGROUND

Increasing unsaturated fat intake is beneficial for cardiovascular health, but the type of unsaturated fat to recommend remains equivocal.

OBJECTIVES

We investigated the effects of an 8-week diet intervention that was rich in either cottonseed oil (CSO; PUFA rich) or olive oil (OO; MUFA rich) on blood lipids in hypercholesterolemic adults.

METHODS

Forty-three men and women with hypercholesterolemia (53 ± 10 years; BMI, 27.6 ± 4.8 kg/m2) completed this randomized parallel clinical trial consisting of an 8-week partial outpatient feeding intervention. Participants were given meals and snacks accounting for ∼60% of their daily energy needs, with 30% of energy needs from either CSO (n = 21) or OO (n = 22). At pre- and postdiet intervention visits, participants consumed a high-SFA meal (35% of total energy needs; 70% of energy from fat). The primary outcomes of fasting cholesterol profiles and secondary outcomes of postprandial blood lipids and glycemic markers were assessed over a 5-hour period.

RESULTS

There were greater reductions from baseline to week 8 in fasting serum total cholesterol (TC; -17.0 ± 3.94 mg/dL compared with -2.18 ± 3.72 mg/dL, respectively; P = 0.008), LDL cholesterol (-19.7 ± 3.94 mg/dL compared with -5.72 ± 4.23 mg/dL, respectively; P = 0.018), non-HDL cholesterol (-20.8 mg/dL ± 4.00 compared with -6.61 ± 4.01 mg/dL, respectively; P = 0.014), and apoB (-11.8 mg/dL ± 2.37 compared with -3.10 ± 2.99 mg/dL, respectively; P = 0.05), in CSO compared with OO. There were also visit effects from baseline to week 8 for increases in HDL cholesterol (CSO, 56.5 ± 2.79 mg/dL to 60.2 ± 3.35 mg/dL, respectively; OO: 59.7 ± 2.63 mg/dL to 64.1 ± 2.24 mg/dL, respectively; P < 0.001), and decreases in the TC:HDL-cholesterol ratio (CSO, 4.30 ± 0.27 mg/dL to 3.78 ± 0.27 mg/dL, respectively; OO, 3.94 ± 0.16 mg/dL to 3.57 ± 0.11 mg/dL, respectively; P < 0.001), regardless of group assignment. In response to the high-SFA meal, there were differences in postprandial plasma glucose (P = 0.003) and triglyceride (P = 0.004) responses and a trend in nonesterified fatty acids (P = 0.11) between groups, showing protection in the postprandial state from an occasional high-SFA fat meal with CSO, but not OO, diet enrichment.

CONCLUSIONS

CSO, but not OO, diet enrichment caused substantial improvements in fasting and postprandial blood lipids and postprandial glycemia in hypercholesterolemic adults. This trial was registered at clinicaltrials.gov as NCT04397055.

Validation of Resting Energy Expenditure Equations in Older Adults with Obesity

It is unclear which energy expenditure prediction equation should guide weight loss interventions in older adults with obesity. We ascertained the validity of four equations commonly used in practice in a series of weight loss studies of adults aged ≥65 with a body mass index ≥30kg/m² using indirect calorimetry data. Diagnostic accuracy was defined as <10% discrepancy between predicted and measured resting metabolic rate (RMR). Mean was 73.4 years. RMR using the ReeVue was 1,643 kCal. With 59.0% accuracy, the WHO equation demonstrated the highest accuracy while the Harris-Benedict yielded 53.5% accuracy. The Owens equation demonstrated the least variability (21.5% overprediction, 27.8% underprediction) with 50.7% accuracy. A SECA bioimpedance analyzer noted the second lowest accuracy of 49.6%. Only 43.1% of measurements were within 10% of the gold-standard indirect calorimetry value using the Mifflin equation. All equations demonstrated <60% accuracy suggesting a great need for estimating energy needs.

Site-Specific Bone Differences and Energy Status in Male Competitive Runners and Road Cyclists

The interaction between mechanical loading and energy availability on bone health in male endurance athletes merits further investigation. The purpose of this study was to compare bone status in male competitive runners and road cyclists and to investigate the influence of energy availability (EA) on bone mineral density (BMD). 18 competitive runners and 19 road cyclists (20-50 years) participated in this study. Areal BMD and body composition were assessed by dual energy x-ray absorptiometry. Volumetric bone variables at the 4% and 66% tibia sites were assessed by peripheral quantitative computed tomography. Energy availability (EA, 7-day dietary and exercise logs) and resting metabolic rate (RMR, open circuit spirometry) were measured as indicators of energy status. Bone loading history, calcium intake, and training history were assessed by questionnaires. After adjusting for age, runners had significantly greater (p < 0.05) areal BMD (femoral neck, left total hip), Z-scores (total body, hips sites), total bone mineral content and trabecular variables (bone mineral content, volumetric BMD, bone strength index) at tibia 4% site, and total volumetric BMD at tibia 66% site than the cyclists (p ≤ 0.05). At the tibia 66% site, cyclists had significantly greater (p < 0.05) total area, periosteal circumference, endosteal circumference, and strength-strain index than runners. Energy variables were similar for runners and cyclists; however, RMR and RMR ratio (measured RMR/predicted RMR) were significantly lower in cyclists (p < 0.001). In conclusion, there were site-specific differences in hip and tibia bone characteristics between runners and cyclists. RMR was associated with several bone outcomes; however, EA was not related to bone health in runners or to dual energy x-ray absorptiometry bone variables in cyclists.

Hypothesized pathways for the association of vitamin D status and insulin sensitivity with resting energy expenditure: a cross sectional mediation analysis in Australian adults of European ancestry

Background

The role of vitamin D in human energy expenditure requires confirmation. We explored whether insulin sensitivity (IS)/insulin resistance (IR) mediated the association of vitamin D status (25OHD) on resting energy expenditure (REE).

Methods

REE, body composition (by DEXA) and clinical biochemistry of 155 Australian men and women were collated. A hypothesized mediation pathway through IS/IR on the direct association between 25OHD and REE was modeled, using three surrogate indices of IS/IR: McAuley’s insulin sensitivity index (McA), Quantitative insulin sensitivity check index (QUICKI) and triglyceride to glucose ratio (TYG). The modeling was performed on PROCESS SPSS Macro (version 4.0) based on 5000 bootstrapped samples, with and without the adjustment for covariates.

Results

Unadjusted models indicated a sizeable negative mediation by all IS/IR indices but no significant direct effect of 25OHD on REE. On adjustment for covariates, a negative indirect mediation effect of McA [β coefficient (SE) −2.1(0.821); bootstrapped 95% CI:−3.934, −0.703; p < 0.05] and a similar negative mediation of TYG [−1.935 (0.780); bootstrapped 95% CI: (−3.679, −0.622; p < 0.05] was observed. These models also showed a positive direct effect of 25OHD on REE. In contrast, QUICKI made a smaller contribution to the total effect though in the same direction as the other two measures [−0.783 (0.534); bootstrapped 95% CI: (−1.939, 0.134; P > 0.05].

Conclusions

A sizeable, partial, negative mediation of IS/IR on the direct relationship between 25OHD and REE, dampened the total effect of vitamin D on REE. Validation of the proposed causal framework would clarify vitamin D’s role in human energy metabolism.

A Smart System for the Contactless Measurement of Energy Expenditure

Energy Expenditure (EE) (kcal/day), a key element to guide obesity treatment, is measured from CO2 production, VCO2 (mL/min), and/or O2 consumption, VO2 (mL/min). Current technologies are limited due to the requirement of wearable facial accessories. A novel system, the Smart Pad, which measures EE via VCO2 from a room's ambient CO2 concentration transients was evaluated. Resting EE (REE) and exercise VCO2 measurements were recorded using Smart Pad and a reference instrument to study measurement duration's influence on accuracy. The Smart Pad displayed 90% accuracy (±1 SD) for 14-19 min of REE measurement and for 4.8-7.0 min of exercise, using known room's air exchange rate. Additionally, the Smart Pad was validated measuring subjects with a wide range of body mass indexes (BMI = 18.8 to 31.4 kg/m2), successfully validating the system accuracy across REE's measures of ~1200 to ~3000 kcal/day. Furthermore, high correlation between subjects' VCO2 and λ for CO2 accumulation was observed (p < 0.00001, R = 0.785) in a 14.0 m3 sized room. This finding led to development of a new model for REE measurement from ambient CO2 without λ calibration using a reference instrument. The model correlated in nearly 100% agreement with reference instrument measures (y = 1.06x, R = 0.937) using an independent dataset (N = 56).

Validity of Estimating the Maximal Oxygen Consumption by Consumer Wearables: A Systematic Review with Meta-analysis and Expert Statement of the INTERLIVE Network

Background

Technological advances have recently made possible the estimation of maximal oxygen consumption (VO_2max) by consumer wearables. However, the validity of such estimations has not been systematically summarized using meta-analytic methods and there are no standards guiding the validation protocols.

Objective

The aim was to (1) quantitatively summarize previous studies investigating the validity of the VO_2max estimated by consumer wearables and (2) provide best-practice recommendations for future validation studies.

Methods

First, we conducted a systematic review and meta-analysis of studies validating the estimation of VO_2max by wearables. Second, based on the state of knowledge (derived from the systematic review) combined with the expert discussion between the members of the Towards Intelligent Health and Well-Being Network of Physical Activity Assessment (INTERLIVE) consortium, we provided a set of best-practice recommendations for validation protocols.

Results

Fourteen validation studies were included in the systematic review and meta-analysis. Meta-analysis results revealed that wearables using resting condition information in their algorithms significantly overestimated VO_2max (bias 2.17 ml·kg⁻¹·min⁻¹; limits of agreement − 13.07 to 17.41 ml·kg⁻¹·min⁻¹), while devices using exercise-based information in their algorithms showed a lower systematic and random error (bias − 0.09 ml·kg⁻¹·min⁻¹; limits of agreement − 9.92 to 9.74 ml·kg⁻¹·min⁻¹). The INTERLIVE consortium proposed six key domains to be considered for validating wearable devices estimating VO_2max, concerning the following: the target population, reference standard, index measure, testing conditions, data processing, and statistical analysis.

Conclusions

Our meta-analysis suggests that the estimations of VO_2max by wearables that use exercise-based algorithms provide higher accuracy than those based on resting conditions. The exercise-based estimation seems to be optimal for measuring VO_2max at the population level, yet the estimation error at the individual level is large, and, therefore, for sport/clinical purposes these methods still need improvement. The INTERLIVE network hereby provides best-practice recommendations to be used in future protocols to move towards a more accurate, transparent and comparable validation of VO_2max derived from wearables.

PROSPERO ID

CRD42021246192.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40279-021-01639-y.

Precision Medicine and Obesity

Obesity is a chronic, relapsing, and multifactorial disease, with a rising prevalence and an associated high economic burden. Achieving successful and sustained weight loss outcomes with current interventions is challenging. This is due, at least in part, to the disease's heterogenous pathophysiology that is yet to be completely understood. Technological advances and greater capabilities for the extraction and storage of information have facilitated the application of precision medicine. Several precision medicine initiatives have been proposed to improve obesity outcomes. Most of these initiatives are based on -omics technologies. Although the data generated from these technologies have led to developing hypotheses that may explain the underpinnings of obesity, their applicability to the clinical practice is yet to be determined. There are other initiatives that have identified quantitative or qualitative physiologic traits that can be targeted and that could have a more immediate clinical impact. This review aims to provide a perspective of current initiatives for precision medicine for obesity.

Energy expenditure due to gluconeogenesis in pathological conditions of insulin resistance

Gluconeogenesis (GNG), the formation of glucose from noncarbohydrate precursors, requires adenosine triphosphate (ATP). Previous studies have estimated the energetic cost of GNG in humans based on theoretical calculations of rates of GNG, moles of oxygen consumption by GNG, and average oxygen consumption. Few human studies have measured the energy expenditure (EE) due to GNG. We estimated EE attributable to GNG in patients with three insulin resistance conditions and high GNG rates (insulin receptor pathogenic variants, lipodystrophy, and type 2 diabetes) and obesity without diabetes. Fractional GNG was measured by incorporation of deuterium from body water into newly formed glucose, endogenous glucose production (EGP) as glucose appearance following administration of [6,6-²H₂]glucose, and total GNG as fractional GNG × EGP. EE was measured by indirect calorimetry and compared with predicted EE from the Mifflin St. Jeor equation. EE attributable to GNG was estimated using linear regression after accounting for age and fat-free mass (FFM). EE in patients with insulin resistance was significantly higher than predicted by the Mifflin St. Jeor equation. GNG correlated with resting EE (REE). EE attributable to GNG in patients with insulin resistance was almost one-third of REE, substantially higher than theorized in healthy subjects. Our findings demonstrate that GNG is a significant contributor to EE in insulin-resistant states. Prediction equations may underestimate caloric needs in patients with insulin resistance. Therefore, targeting caloric needs to account for higher EE due to increased GNG should be considered in energy balance studies in patients with insulin resistance.NEW & NOTEWORTHY Gluconeogenesis is an energy-requiring process that is upregulated in diabetes, contributing to hyperglycemia. Previous studies have estimated that gluconeogenesis accounts for less than 10% of resting energy expenditure. This study estimates the energy expenditure attributable to gluconeogenesis in uncommon and severe forms of insulin resistance and common, milder forms of insulin resistance. In these populations, gluconeogenesis accounts for almost one-third of resting energy expenditure, substantially higher than previously theorized in the literature.

Ruiz J, Amaro-Gahete FJ. Inter-Day Reliability of Resting Metabolic Rate and Maximal Fat Oxidation during Exercise in Healthy Men Using the Ergostik Gas Analyzer

The attainment of high inter-day reliability is crucial to determine changes in resting metabolic rate (RMR), respiratory exchange ratio (RER), maximal fat oxidation during exercise (MFO) and the intensity that elicits MFO (Fatmax) after an intervention. This study aimed to analyze the inter-day reliability of RMR, RER, MFO and Fatmax in healthy adults using the Ergostik gas analyzer. Fourteen healthy men (age: 24.4 ± 5.0 years, maximum oxygen uptake (VO₂max): 47.5 ± 11.9 mL/kg/min) participated in a repeated-measures study. The study consisted of two identical experimental trials (Day 1 and Day 2) in which the participants underwent an indirect calorimetry assessment at resting and during an incremental exercise test. Stoichiometric equations were used to calculate energy expenditure and substrate oxidation rates. There were no significant differences when comparing RMR (1999.3 ± 273.9 vs. 1955.7 ± 362.6 kcal/day, p = 0.389), RER (0.87 ± 0.05 vs. 0.89 ± 0.05, p = 0.143), MFO (0.32 ± 0.20 vs. 0.31 ± 0.20 g/min, p = 0.776) and Fatmax (45.0 ± 8.6 vs. 46.4 ± 8.4% VO₂max, p = 0.435) values in Day 1 vs. Day 2. The inter-day coefficient of variation for RMR, RER, MFO and Fatmax were 4.85 ± 5.48%, 3.22 ± 3.14%, 7.78 ± 5.51%, and 6.51 ± 8.04%, respectively. In summary, the current results show a good inter-day reliability when RMR, RER, MFO and Fatmax are determined in healthy men using the Ergostik gas analyzer.

Pecan-enriched diets increase energy expenditure and fat oxidation in adults at-risk for cardiovascular disease in a randomised, controlled trial

BACKGROUND

Research indicates that diets enriched with unsaturated fatty acids improve energy metabolism, although studies on tree nuts, which are a rich source of those fats, are limited. The present study aimed to examine the impact of daily pecan consumption for 8 weeks on energy metabolism in adults with hypercholesterolaemia or at higher risk for cardiovascular disease (CVD) (body mass index ≥ 28 kg m^-2 ).

METHODS

For this randomised, controlled trial, 56 sedentary adults were randomised into one of three treatments for an 8-week intervention: two pecan groups and a nut-free control group (n = 18). The ADD group (n = 16) consumed pecans as part of a free-living diet, whereas the SUB group (n = 18) substituted the pecans for isocaloric foods from their habitual diet. At baseline and 8 weeks, a high saturated fat meal was consumed along with indirect calorimetry measurements at fasting and for 4 h postprandially to determine changes in resting metabolic rate (RMR), diet induced thermogenesis (DIT) and substrate utilisation (primary outcomes). Forty-seven participants completed the trial and were included in analyses.

RESULTS

In the SUB group, there was an increase in fasting RMR (1607 ± 117 to 1701 ± 114 kcal day^-1 ; p = 0.01) and fasting fat oxidation (0.83 ± 0.08 to 0.99 ± 0.08 g/15 min; p = 0.009) and a decrease in fasting respiratory exchange ratio (0.85 ± 0.01 to 0.83 ± 0.01; p = 0.05) from pre- to post-intervention. In the ADD group, there was an increase in postprandial DIT (p < 0.001). There were no changes within the control group or between groups for any outcome measure.

CONCLUSIONS

Daily consumption of pecans may increase select measures of energy expenditure and fat oxidation in adults at-risk for CVD.

CYP1A2 Genotype Polymorphism Influences the Effect of Caffeine on Anaerobic Performance in Trained Males

The purpose was to investigate the effects of CYP1A2 -163C > A polymorphism on the effects of acute caffeine (CAF) supplementation on anaerobic power in trained males. Sixteen trained males (age: 21.6 ± 7.1 years; height: 179.7 ± 5.6 cm; body mass: 72.15 ± 6.8 kg) participated in a randomized, double-blind, placebo (PLA) controlled crossover design. Participants supplemented with CAF (6 mg/kg of body mass) and an isovolumetric PLA (maltodextrin) in random order and separated by 7 days, before an all-out 30-s anaerobic cycling test to determine peak, average, and minimum power output, and fatigue index. Genomic deoxyribonucleic acid was extracted to identify each participants CYP1A2 genotype. Six participants expressed AA homozygote and 10 expressed C alleles. There was a treatment by genotype interaction for peak power output (p = .041, η2 = .265, observed power = 0.552) with only those expressing AA genotype showing improvement following CAF supplementation compared with PLA (CAF: 693 ± 108 watts vs. PLA: 655 ± 97 watts; p = .039), while no difference between treatments was noted in those expressing C alleles (CAF: 614 ± 92 watts vs. PLA: 659 ± 144 watts; p = .135). There were no other interaction or main effects for average or minimum power output, or fatigue index (p > .05). In conclusion, the ingestion of 6 mg/kg of CAF improved peak power output only in participants with the AA genotype compared with PLA; however, expression of the CYP1A2 did not influence average or minimum power output or fatigue index.

Predictive Accuracy of the Nelson Equation via BodPod Compared to Commonly Used Equations to Estimate Resting Metabolic Rate in Adults

Indirect calorimetry (IC) is considered the gold standard for assessing resting metabolic rate (RMR). However, many people do not have access to IC devices and use prediction equations for RMR estimation. Equations using fat free mass (FFM) as a predictor have been developed to estimate RMR, as a strong relationship exists between FFM and RMR. One such equation is the Nelson equation which is used by the BodPod (BP). Yet, there is limited evidence whether the Nelson equation is superior to other common equations to predict RMR. To examine the agreement between predicted RMR from common RMR equations and the BP, and RMR measured via IC. Data from 48 healthy volunteers who completed both the BP and IC were collected. Agreement between RMR measured by BP, common regression equations, and indirect caloriometry was evaluated using repeated measures ANOVA, Bland-Altman analysis and root mean square error (RMSE). Predicted RMR values from common equations and BP were significantly different from IC with the exception of the World Health Organization (WHO) equation. Large limits of agreement and RMSE values demonstrate a large amount of error at the individual level. Despite the use of FFM, the Nelson equation does not appear to be superior to other common RMR equations. Although the WHO equation presented the best option within our sample, all equations performed poorly at the individual level. Clinicians should be aware that prediction equations may significantly under- or overestimate RMR compared to IC and when an accurate value of RMR is required, IC is recommended.

Pecan-Enriched Diets Alter Cholesterol Profiles and Triglycerides in Adults at Risk for Cardiovascular Disease in a Randomized, Controlled Trial

BACKGROUND

Research indicates that tree nuts are cardioprotective, but studies on pecans are limited.

OBJECTIVES

We examined the impact of daily pecan consumption on blood lipids and glycemia in adults at-risk for cardiovascular disease (CVD).

METHODS

This was a randomized, controlled trial where 56 adults (BMI ≥28 kg/m2 or hypercholesterolemia) were randomly allocated into a control group (n = 18) or 1 of 2 pecan groups. The ADD group (n = 16) consumed pecans (68 g) as part of a free-living diet. The SUB group (n = 18) substituted the pecans (68 g) for isocaloric foods from their diet. At baseline and 8 wk, a high-fat meal was consumed with 4-h postprandial blood draws to determine changes in blood lipids and glycemia.

RESULTS

There was a significant reduction from baseline to 8 wk in fasting total cholesterol (TC) (204 ± 8.76 to 195 ± 8.12; 205 ± 8.06 to 195 ± 6.94 mg/dL), LDL cholesterol (143 ± 8.09 to 129 ± 7.71; 144 ± 6.60 to 135 ± 6.16 mg/dL), triglycerides (TGs) (139 ± 12.1 to 125 ± 14.6; 133 ± 10.7 to 120 ± 10.3 mg/dL), TC/HDL cholesterol ratio (3.92 ± 0.206 to 3.58 ± 0.175; 4.08 ± 0.167 to 3.79 ± 0.151), non-HDL cholesterol (151 ± 8.24 to 140 ± 7.95; 155 ± 6.87 to 143 ± 6.00 mg/dL), and apolipoprotein B (99.1 ± 5.96 to 93.0 ± 5.35; 104 ± 3.43 to 97.1 ± 3.11 mg/dL) in the ADD and SUB groups, respectively (P ≤ 0.05 for all), with no changes in control. There was a reduction in postprandial TGs (P ≤ 0.01) in ADD, and a reduction in postprandial glucose (P < 0.05) in SUB.

CONCLUSIONS

Pecan consumption improves fasting and postprandial blood lipids in CVD at-risk adults. This trial was registered at clinicaltrials.gov as NCT04376632.

Pecan-enriched diets decrease postprandial lipid peroxidation and increase total antioxidant capacity in adults at-risk for cardiovascular disease

Pecans are a rich source of antioxidants, but the effect of regular consumption on post-meal responses is unknown. The objective of this study was to examine the impact of daily pecan consumption for 8 weeks on fasting and postprandial lipid peroxidation, total antioxidant capacity (TAC), and tocopherols in adults at higher risk for cardiovascular disease (CVD) (hypercholesterolemia or elevated adiposity). We hypothesized that daily pecan consumption would result in increased fasting γ-tocopherol, increased fasting and postprandial TAC, and decreased fasting and postprandial lipid peroxidation. This was a randomized, parallel, controlled trial with 3 treatments: two pecan groups and a nut free control (n = 16). The ADD group (n = 15) consumed pecans as part of a free-living diet, and the SUB group (n = 16) substituted the pecans for isocaloric foods from their habitual diet. At the pre- and post-intervention, a high saturated fat breakfast shake was consumed with postprandial blood draws over 2h. In the ADD and SUB groups, postprandial lipid peroxidation was suppressed (iAUC: 0.9 ± 1.3 to -2.9 ± 2.0 and 4.5 ± 1.7 to 0.7 ± 1.1 µM/2h, respectively; P <0.05) and TAC was elevated (iAUC: -240.8 ± 110.2 to 130.9 ± 131.7 and -227.6 ± 131.2 to 208.7 ± 145.7 µM Trolox Equivalents/2h, respectively; P <0.01) from pre- to post-intervention. Furthermore, there was an increase in γ-tocopherol from pre- to post-intervention within the ADD (1.4 ± 0.1 to 1.8 ± 0.1 µg/mL; P <0.001) and SUB groups (1.8 ± 0.2 to 2.1 ± 0.2 µg/mL; P <0.05). There were no changes in any variable within the control group. These findings suggest that daily pecan consumption protects against oxidative stress that occurs following a high-fat meal in adults at risk for CVD.

A Handheld Metabolic Device (Lumen) to Measure Fuel Utilization in Healthy Young Adults: Device Validation Study

Background

Metabolic carts measure the carbon dioxide (CO₂) produced and oxygen consumed by an individual when breathing to assess metabolic fuel usage (carbohydrates versus fats). However, these systems are expensive, time-consuming, and only available in health care laboratory settings. A small handheld device capable of determining metabolic fuel usage via CO₂ from exhaled air has been developed.

Objective

The aim of this study is to evaluate the validity of a novel handheld device (Lumen) for measuring metabolic fuel utilization in healthy young adults.

Methods

Metabolic fuel usage was assessed in healthy participants (n=33; mean age 23.1 years, SD 3.9 years) via respiratory exchange ratio (RER) values obtained from a metabolic cart as well as % CO₂ from the Lumen device. Measurements were performed at rest in two conditions: fasting, and after consuming 150 grams of glucose, in order to determine changes in metabolic fuel usage. Reduced major axis regression and simple linear regression were performed to test for agreement between RER and Lumen % CO₂.

Results

Both RER and Lumen % CO₂ significantly increased after glucose intake (P<.001 for both) compared with fasting conditions, by 0.089 and 0.28, respectively. Regression analyses revealed an agreement between the two measurements (F_1,63=18.54; P<.001).

Conclusions

This study shows the validity of Lumen for detecting changes in metabolic fuel utilization in a comparable manner with a laboratory standard metabolic cart, providing the ability for real-time metabolic information for users under any circumstances.

Selection of Antiobesity Medications Based on Phenotypes Enhances Weight Loss: A Pragmatic Trial in an Obesity Clinic

OBJECTIVE

Little is known about the predictors of response to obesity interventions.

METHODS

In 450 participants with obesity, body composition, resting energy expenditure, satiety, satiation, eating behavior, affect, and physical activity were measured by validated studies and questionnaires. These variables were used to classify obesity phenotypes. Subsequently, in a 12-month, pragmatic, real-world trial performed in a weight management center, 312 patients were randomly assigned to phenotype-guided treatment or non-phenotype-guided treatment with antiobesity medications: phentermine, phentermine/topiramate, bupropion/naltrexone, lorcaserin, and liraglutide. The primary outcome was weight loss at 12 months.

RESULTS

Four phenotypes of obesity were identified in 383 of 450 participants (85%): hungry brain (abnormal satiation), emotional hunger (hedonic eating), hungry gut (abnormal satiety), and slow burn (decreased metabolic rate). In 15% of participants, no phenotype was identified. Two or more phenotypes were identified in 27% of patients. In the pragmatic clinical trial, the phenotype-guided approach was associated with 1.75-fold greater weight loss after 12 months with mean weight loss of 15.9% compared with 9.0% in the non-phenotype-guided group (difference -6.9% [95% CI -9.4% to -4.5%], P < 0.001), and the proportion of patients who lost >10% at 12 months was 79% in the phenotype-guided group compared with 34% with non-phenotype-guided treatment group.

CONCLUSIONS

Biological and behavioral phenotypes elucidate human obesity heterogeneity and can be targeted pharmacologically to enhance weight loss.

Weight change adjusted equations for assessing resting metabolic rate in overweight and obese adults

BACKGROUND

Although over one hundred equations have been developed to predict the energy expenditure of individuals, none are sensitive to weight change in assessment of resting metabolic rate (RMR) before and after weight loss.

OBJECTIVE

To formulate adjusted equations for overweight and obese individuals and to compare their accuracy with existing prediction RMR equations before and after weight loss.

SUBJECTS/MATERIALS

This is historical prospective study. Participants included 39 overweight and obese men and women before and after losing 10-20% from baseline weight on a diet and physical activity regimen for at least three months. Pre and post weight loss measured RMR results were compared to estimated RMR using several existing prediction equations: Harris and Benedict, Ravussin and Bogardus, and Mifflin et al. To improve the accuracy of these prediction equations, we suggest new equations adjusted for weight loss, based on measured RMR and evaluated their accuracy.

RESULTS

Pre and post weight loss data indicated: significant fat reduction in both genders; reduction in free-fat mass only in men, and a significant decrease in measured RMR only in women. Our suggested equations were the most accurate and closest to measured RMR in both genders, in comparison to the Harris and Benedict, Ravussin and Bogardus, and Mifflin et al equation results. Estimated RMR using the latter equations was significantly lower than measured RMR in both genders at pre and post weight loss (P < 0.01).

CONCLUSIONS

This study highlights the need for adjusting RMR equations before and after weight loss in overweight and obese individuals. Further research is needed to validate our suggested equations.

Design of a randomised controlled trial: does indirect calorimetry energy information influence weight loss in obesity?

INTRODUCTION

Respiratory quotient (RQ) provides an indication of the relative balance of carbohydrate and fat oxidation. RQ could serve as an early biomarker of negative energy balance during weight loss. Restriction of energy intake relative to total daily energy requirements produces a negative energy balance which can lead to a fall in RQ, accompanied by a decrease in resting energy expenditure (REE). However, the net change in body weight does not usually match predicted weight change due to intraindividual metabolic adaptations. Our aim is to determine the effectiveness of utilising EE information from indirect calorimetry during weight loss intervention.

METHODS AND ANALYSIS

We will undertake an assessor-blinded, parallel-group randomised controlled trial of 105 adults with obesity randomised in 1:1 ratio to receive either standard weight management care (SC) or EE information plus SC (INT) during a 24-week multicomponent weight management programme. The primary outcome is difference in weight loss between INT and SC group at 24 weeks. Secondary outcomes include: change in RQ, REE, glycaemic variability, and appetite-relating gut hormones (glucagon-like peptide 1, gastric inhibitory polypeptide, peptide YY). Generalised linear mixed models (intention to treat) will assess outcomes for treatment (INT vs SC), time (baseline, 24 weeks) and the treatment-by-time interaction. This will be the first study to evaluate impact of utilising measured REE and RQ on the lifestyle-based intensive intervention programme.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the Health Research Authority and the North West Research Ethics Committee (18/NW/0645). Results from this trial will be disseminated through publication in peer-reviewed journals, national and international presentations.

TRIAL REGISTRATION NUMBERS

NCT03638895; UoL001379.

Psychological Resilience, Experimentally Manipulated Social Status, and Dietary Intake among Adolescents

Relative to other racial/ethnic groups in the United States, Hispanic American (HA) youth have higher rates of overweight and obesity. Previous work suggests that low perceived social status (SS) promotes excess caloric intake and, thereby, development of obesity. Psychological resilience may play a role in reducing adverse eating behaviors and risk for obesity. The objective of this study was to investigate whether resilience (as measured by the Connor Davidson Resilience Scale) interacts with experimentally manipulated SS to affect dietary intake among HA adolescents (n = 132). Using a rigged game of Monopoly (Hasbro, Inc.), participants were randomized to a high or low SS condition. Following the Monopoly game, participants consumed an ad libitum lunch and their dietary intake was assessed. There was a significant interaction between resilience and experimentally manipulated SS for total energy intake (p = 0.006), percent energy needs consumed (p = 0.005), and sugar intake (p = 0.004). For the high SS condition, for each increase in resilience score, total energy intake decreased by 7.165 ± 2.866 kcal (p = 0.014) and percent energy needs consumed decreased by 0.394 ± 0.153 (p = 0.011). In the low SS condition, sugar intake increased by 0.621 ± 0.240 g for each increase in resilience score (p = 0.011). After correction for multiple comparisons, the aforementioned interactions, but not simple slopes, were statistically significant.

Pathophysiological role of metabolic flexibility on metabolic health

Glucose, fatty acids, and amino acids among others are oxidized to generate adenosine triphosphate (ATP). These fuels are supplied from the environment (through food intake) and internal depots (through lipolysis, glycogenolysis, and proteolysis) at different rates throughout the day. Complex adaptive systems permit to accommodate fuel oxidation according to fuel availability. This capacity of a cell, tissue, or organism to adapt fuel oxidation to fuel availability is defined as metabolic flexibility (MetF). There are conditions, such as insulin resistance, diabetes, and obesity, in which MetF seems to be impaired. The observation that those conditions are accompanied by mitochondrial dysfunction has set the basis to propose a link between mitochondrial dysfunction, metabolic inflexibility, and metabolic health. We here highlight the evidence about the notion that MetF influences metabolic health.

Effectiveness of Rice Germ Supplementation on Body Composition, Metabolic Parameters, Satiating Capacity, and Amino Acid Profiles in Obese Postmenopausal Women: A Randomized, Controlled Clinical Pilot Trial

Rice germ (RG) may be a safe and effective dietary supplement for obesity in menopause, considering its high protein content and considerable amounts of essential amino acids, good fatty acids, and fiber. This pilot randomized, blinded, parallel-group, placebo-controlled pilot trial investigated the effectiveness of 4-weeks RG supplementation (25 g twice a day) on body composition, as primary outcome, measured by Dual Energy X-Ray Absorptiometry (DXA), and metabolic parameters, as secondary outcomes, like amino acid profiles and satiating capacity, in obese postmenopausal women following a tailored hypocaloric diet (25–30% less than daily energy requirements). Twenty-seven women were randomly assigned to the supplemented group (14) or placebo group (13). There was a significant interaction between time and group for body mass index (BMI) (p < 0.0001), waist (p = 0.002) and hip circumferences (p = 0.01), total protein (0.008), albumin (0.005), Homeostasis Model Assessment index score (p = 0.04), glycine (p = 0.002), glutamine (p = 0.004), and histidine (p = 0.007). Haber’s means over time showed a clearly greater feeling of satiety for the supplemented compared to the placebo group. These findings indicate that RG supplementation in addition to a tailored diet counterbalanced the metabolic changes typical of menopause, with improvements in BMI, body composition, insulin resistance, amino acid profiles, and satiety.

Energy expenditure and indirect calorimetry in critical illness and convalescence: current evidence and practical considerations

The use of indirect calorimetry is strongly recommended to guide nutrition therapy in critically ill patients, preventing the detrimental effects of under- and overfeeding. However, the course of energy expenditure is complex, and clinical studies on indirect calorimetry during critical illness and convalescence are scarce. Energy expenditure is influenced by many individual and iatrogenic factors and different metabolic phases of critical illness and convalescence. In the first days, energy production from endogenous sources appears to be increased due to a catabolic state and is likely near-sufficient to meet energy requirements. Full nutrition support in this phase may lead to overfeeding as exogenous nutrition cannot abolish this endogenous energy production, and mitochondria are unable to process the excess substrate. However, energy expenditure is reported to increase hereafter and is still shown to be elevated 3 weeks after ICU admission, when endogenous energy production is reduced, and exogenous nutrition support is indispensable. Indirect calorimetry is the gold standard for bedside calculation of energy expenditure. However, the superiority of IC-guided nutritional therapy has not yet been unequivocally proven in clinical trials and many practical aspects and pitfalls should be taken into account when measuring energy expenditure in critically ill patients. Furthermore, the contribution of endogenously produced energy cannot be measured. Nevertheless, routine use of indirect calorimetry to aid personalized nutrition has strong potential to improve nutritional status and consequently, the long-term outcome of critically ill patients.

Variance in respiratory quotient among daily activities and its association with obesity status

BACKGROUND/OBJECTIVES

The ability to adapt the level of daily fuel utilization to substrate availability is given by the respiratory quotient (RQ), which its variance is an indicator of metabolic flexibility. Metabolic inflexibility is associated with many pathologies including obesity, but evidence relies on bed-rest studies and exercise-based interventions. Our goal was to examine the associations for RQ variance in response to daily living activities with obesity, in healthy adults.

SUBJECTS/METHODS

Participants (N = 50; 25 women), 20-64 years were lying for 60 min and randomly performed three conditions for 10 min each (sitting, standing, 1 sit/stand/sit transition min-1). RQ was measured by indirect calorimetry and fat mass (FM), trunk FM (TFM), and fat-free mass (FFM) by DXA.

RESULTS

RQ variance among the three conditions was inversely associated with BMI (ß = 0.005; p < 0.001), FM (ß = 0.007; p = 0.024), and TFM (ß = 0.008; p = 0.026). A positive association was found between RQ variance and FFM (ß = -0.007; p = 0.024). No interactions for sex were found (p ≥ 0.05).

CONCLUSIONS

These findings suggest that a higher RQ variance in response to daily living metabolic challenges such as transitioning between sitting and standing is associated with lower overall and central obesity, as well as with a higher FFM, in healthy adults. Thus, RQ variance may work as an indication of metabolic flexibility, but these findings were obtained in a young and non-obese adult population without considering their fitness levels. Thus, further research in this field is warranted.