Intra-individual variation in RMR in older people

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.

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.

Standard Equations Are Not Accurate in Assessing Resting Energy Expenditure in Patients With Amyotrophic Lateral Sclerosis

OBJECTIVE

To assess the utility of standard equations for calculating caloric requirements in patients with amyotrophic lateral sclerosis (ALS).

BACKGROUND

Malnutrition substantially increases the risk of death in ALS. Weight loss can be stabilized and survival prolonged with early gastrostomy feeding. However the use of standard nutrition equations has not been validated in this population. We therefore compared measured caloric expenditure to 2 predictive equations in patients with varying stages of ALS.

METHODS

Thirty-four patients were studied. Caloric expenditure and respiratory quotient (R) were measured using indirect calorimetry. Results were compared with the Harris-Benedict equation.

RESULTS

The prediction error for the Harris-Benedict equation was 18.6 + 14.9%. Limits of agreement showed this equation could overestimate caloric expenditure by 591 kcal/d and underestimate requirements by 677 kcal/d. R was >0.86 in 11 patients, suggesting overfeeding, and <0.8 in 15 patients, suggesting underfeeding. The difference between predicted and measured caloric expenditure did not correlate with disease severity, disease duration, or body mass index. Mechanically ventilated patients had higher than predicted energy expenditure.

CONCLUSIONS

We found that standard equations used to calculate energy expenditure were not valid for patients with ALS. Moreover, the majority of our patients were either overfed or underfed. As underfeeding can cause diaphragm impairment, and overfeeding can increase ventilatory load, indirect calorimetry should be considered in ALS patients to determine optimal caloric requirement.

Comparison of the GEM and the ECAL indirect calorimeters against the Deltatrac for measures of RMR and diet-induced thermogenesis

The Deltatrac™ II Metabolic Monitor (Datex-Ohmeda Inc.) is considered the standard reference machine in indirect calorimetry; however, it is no longer commercially available thus there is a need for new machines. The gas exchange measurement (GEM; GEM Nutrition Ltd) and the ECAL (Health Professional Solutions) are alternative measuring systems. The aim of this study was to compare the ECAL and GEM with Deltatrac for measures of RMR and the GEM to the Deltatrac for measures of diet-induced thermogenesis (DIT). Twenty healthy participants were tested on test day 1 (T1) and test day 2 (T2). RMR was measured in a randomised order for 30 min on the Deltatrac, the GEM and the ECAL. Following this, a 1553 kJ meal was consumed and DIT was measured on the Deltatrac and the GEM in alternating 15 min intervals for 4 h. The GEM reported consistently higher values than the Deltatrac for VO2, VCO2, RMR and fat oxidation (P < 0·005). The ECAL was significantly higher than the Deltatrac for measures of VO2, RMR, carbohydrate oxidation (T2) and respiratory quotient and fat oxidation (T1, T2) (P < 0·05). There were no significant differences within repeated RMR measures on the ECAL, the GEM or the Deltatrac. DIT measures were consistently higher on the GEM (T1) (P < 0·005); however, there were no significant differences between repeated measures. The findings suggest that while the GEM and the ECAL were not accurate alternatives to the Deltatrac, they may be reliable for repeated measures.

Increased resting energy expenditure in children with attention-deficit-hyperactivity disorder

BACKGROUND

Attention Deficit Hyperactivity Disorder (ADHD) is one of the most frequently reported neuropsychiatric disorders in childhood. However, there is limited data on the biological basis for this disorder. Disturbances in neurotransmitters have been suggested to play a pathophysiologic role. Phenotypically an increased prevalence of obesity has been reported.

OBJECTIVE

To investigate resting energy expenditure (REE) and diet-induced thermogenesis in stimulant medication-naïve children with ADHD.

DESIGN

Case control study of 12 pre-pubertal boys with ADHD of the hyperactive-impulsive type and 12 control boys without ADHD. Anthropometric testing and indirect calorimetry were performed before and after a standardized meal. REE and thermogenesis were measured in each subject at 2 time points. In an independent group of 60 boys with ADHD, BMI standard deviation scores (BMI-SDS) were compared to age-adapted reference values.

RESULTS

REE was on average 6.5 kcal/kg fat free mass/day higher in the ADHD compared to the control group (p<0.01). In contrast, the thermogenic effect of food was not different between the two groups (average increase by 16%, p=n.s.). The repeat measurements, an average of 5±1 months apart, were highly reproducible in all subjects. Age and restlessness did not explain the differences in REE. Boys with ADHD had similar BMI-SDS values (mean BMI-SDS -0.10±0.98) as reference groups.

CONCLUSIONS

REE, in contrast to diet-induced thermogenesis, is higher in medication-naïve boys with ADHD. The normal BMI levels suggest increased energy intake in these children.

[Resting metabolic rate and body composition in postmenopausal women]

OBJECTIVE

The present study evaluated the relationship between resting metabolic rate (RMR) and body composition of postmenopausal women.

METHODS

Thirty physically inactive women participated in the study, and their age average was 54,33 +/- 5,20 years old. Oxygen consumption was measured by indirect calorimetry after 12 hours of fasting and the values were calculated according to the equation of Weir. Body composition was obtained by the method of skinfolds and the measurement of waist circumference (WC) was used to assess abdominal fat. The linear correlation of Pearson was used to establish correlations between the variables.

RESULTS

We found significant correlations of TMR with the CC (0.42) and the lean mass (LM) (r = 0.48).

CONCLUSIONS

The variables of body composition that can be involved in the determination of the RMR are LM and WC.

Past and current body size affect validity of reported energy intake among middle-aged Danish men

Our objectives were to estimate the degree of misreporting energy intake (EI) and analyze associations with previous BMI, current BMI, or both. The study was part of the Adiposity and Genetics Study follow-up study including 309 Danish men (age 40-65 y) originally sampled from the obligatory draft board examination. Height and weight were measured at the mean ages of 20 (draft board), 33, 44, and 49 y (current age). Obesity was categorized as BMI >or= 31 kg/m(2). Dietary intake for 7 d and physical activity (PA) level (PAL) were self-reported. Resting metabolic rate (RMR) was measured in a ventilated hood system. By comparing EI with energy expenditure and assuming energy balance, reporting accuracy (RA) was estimated as EI/(RMR.PAL). A plausibility interval was calculated to encompass specific variation components of EI, RMR, and PAL; the specific 95% plausibility interval was 1.00 +/- 0.35. Participants were categorized as underreporters (RA <or= 0.65), plausible reporters (0.65 < RA <or= 1.35), or overreporters (RA > 1.35) of EI. The relation between RA and BMI was studied through linear regression analysis. Overall, the RA was (mean +/- SE) 0.76 +/- 0.01. Of 309 participants, 35% underreported and 7% overreported. Whether stratified for current BMI or draft board BMI, the obese men were more likely to underreport than those who were not obese. Among those currently not obese, underreporting was more prevalent among those who were obese at the draft board examination (44%) than among those who were not (21%). Regression analysis showed that both previous and current BMI and their combination were significantly associated with RA. Thus, underreporting of dietary intake seems to be associated with not only current BMI but also with current BMI in combination with previous BMI.

Metabolic testing in the office

The three most commonly used metabolic tests are the Resting Metabolic Rate, Anaerobic Threshold Testing, and V.O2max. For several decades, these metabolic tests have been confined to the setting of university-based physiology laboratories and cardiopulmonary environments, i.e., metabolic carts in the intensive care units. The information gathered is used as a research and clinical tool in evaluating metabolic activity in a variety of physiological states from a body at rest, to exercise (aerobic and anaerobic), in certain medical states like illness, fed/starvation, and medicinal or supplementation affective states. Over the last decade, as technology has improved, so have the metabolic testing carts. They have become widely available for mainstream use by a variety of health care professionals. The purpose of this article is to review these three tests and how they may be useful in a medical practice.

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.

Variability in energy expenditure and its components

PURPOSE OF REVIEW

To review factors contributing to variation in total daily energy expenditure and its primary components: (1) resting metabolic rate; (2) diet-induced thermogenesis; and (3) activity thermogenesis, including exercise energy expenditure and nonexercise activity. For each component, the expected magnitude of intra-individual variability is also considered. We also reviewed studies that quantified the variability in 24 h energy expenditure.

RECENT FINDINGS

In humans, the coefficient of variation in the components of total daily energy expenditure is around 5-8% for resting metabolic rate, 1-2% for exercise energy expenditure, and around 20% for diet-induced thermogenesis. The coefficient of variance for 24 h energy expenditure measured using a room calorimeter for resting metabolic rate is around 5-10%. Thus, these measures are all rather reproducible. Total daily energy expenditure varies several-fold in humans, not due to variation in resting metabolic rate, diet-induced thermogenesis, or exercise thermogenesis, but rather, due to variations in nonexercise activity. A variety of factors impact nonexercise activity, including occupation, environment, education, genetics, age, gender, and body composition, but little is known about the magnitude of effect.

SUMMARY

Resting metabolic rate, diet-induced thermogenesis, exercise energy expenditure, and 24 h energy expenditure are highly reproducible. Coefficient of variation is smallest for exercise energy expenditure, followed by resting metabolic rate, 24 h energy expenditure, and diet-induced thermogenesis. There is considerable variability in total daily energy expenditure, largely due to variations in nonexercise activity. Although the factors that impact upon nonexercise activity are understood, their contribution to variation in total daily energy expenditure is unclear.