Whole-room Indirect Calorimetry Research Articles

127-OR: The Effect of Tirzepatide during Weight Loss on Metabolic Adaption, Fat Oxidation, and Food Intake in People with Obesity

We hypothesized that tirzepatide (TZP) causes body weight loss by reducing food intake and, according to pre-clinical studies, decreasing metabolic adaptation during weight loss. In a randomized blinded clinical trial in people with obesity (PWO) undergoing caloric restriction, we investigated the effect of TZP vs Placebo (PBO) on energy metabolism after targeting a 10% (±2%) weight loss. In this 18wk phase 1 study, 55 PWO, were randomized (1:1) to TZP 15 mg or PBO (mean baseline body weight 102.5 vs 103.1 kg, respectively). The primary objective was to investigate the change from baseline in sleeping metabolic rate (SMR) measured by whole-room indirect calorimetry. Secondary measures were changes in 24-hr sedentary energy expenditure, 24-hr respiratory quotient (RQ), sleeping RQ, substrate utilization, body composition (BC) and food intake. TZP caused greater weight loss than PBO (-16.7 kg vs -8.3 kg; p<0.001). The decreases in SMR and 24-hr energy expenditure were not different between groups after adjusting for changes in body weight and BC. However, TZP significantly reduced 24-hr RQ and sleeping RQ compared to PBO; thus, significantly increasing fat oxidation while decreasing carbohydrate and protein oxidation rates. TZP also significantly reduced food intake. Overall, TZP did not affect metabolic adaptation but significantly increased fat oxidation. Disclosure E.Ravussin: Advisory Panel; Novartis, Research Support; Eli Lilly and Company, Novartis AG. A.Haupt: Employee; Lilly, Stock/Shareholder; Lilly. G.Sanchez-delgado: Research Support; Eli Lilly and Company, Novo Nordisk, Abbott, Maastricht instruments, Vyaire Medical, ParvoMedics, Cosmed, Speaker's Bureau; Eli Lilly and Company. C.K.Martin: Board Member; EHE Health, Wondr Health, Other Relationship; ABGIL, Research Support; Pack Health, Evidation Health, Lilly, WW International, Inc. H.Nishiyama: None. J.Li: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. S.Urva: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. E.J.Pratt: Employee; Eli Lilly and Company. T.Coskun: Employee; Eli Lilly and Company, Stock/Shareholder; Eli Lilly and Company. Z.Milicevic: Employee; Eli Lilly and Company. Funding Eli Lilly and Company

How can we assess "thrifty" and "spendthrift" phenotypes?

There is a large inter-individual variability in the magnitude of body weight change that cannot be fully explained by differences in daily energy intake and physical activity levels and that can be attributed to differences in energy metabolism. Measuring the short-term metabolic response to acute changes in energy intake can better uncover this inter-individual variability and quantify the degree of metabolic thriftiness that characterizes an individual's susceptibility to weight gain and resistance to weight loss. This review summarizes the methods used to identify the individual-specific metabolic phenotype (thrifty vs. spendthrift) in research and clinical settings. The metabolic responses to short-term fasting, protein-imbalanced overfeeding, and mild cold exposure constitute quantitative factors that characterize metabolic thriftiness. The energy expenditure response to prolonged fasting is considered the most accurate and reproducible measure of metabolic thriftiness, likely because the largest energy deficit best captures interindividual differences in the extent of metabolic slowing. However, all the other dietary/environmental challenges can be used to quantify the degree of thriftiness using whole-room indirect calorimetry. Efforts are underway to identify alternative methods to assess metabolic phenotypes in clinical and outpatient settings such as the hormonal response to low-protein meals.

A New Approach to Improve the Validity of Doubly Labeled Water to Assess CO2 Production during High-Energy Turnover.

Accurate measurement of energy expenditure (EE) using doubly labeled water depends on the estimate of total body water (TBW). The aims of this study were to 1) assess the accuracy of a new approach for estimating TBW and EE during high-energy turnover and 2) assess the accuracy of day-to-day assessment of EE with this new approach. EE was measured in six healthy subjects (three male) for 5 consecutive days using three doubly labeled water methods: 1) the plateau, 2) slope-intercept, and 3) overnight-slope method, with whole-room indirect calorimetry as reference method. Urine samples were collected every evening and morning. High EE (physical activity level of >2.5) was achieved by cycling 4 h·d-1. Physical activity level was 2.8 ± 0.1. TBW values were 41.9 ± 6.1, 38.4 ± 5.7, and 40.4 ± 5.8 L for the plateau, slope-intercept, and overnight-slope methods, respectively. The overnight-slope method showed the highest accuracy in estimated CO2 production, when compared with indirect calorimetry over the complete 5-d period (mean ± SD difference, 0.9% ± 1.6%). The plateau method significantly overestimated CO2 production by 4.7% ± 2.6%, whereas the slope-intercept method underestimated CO2 production (-3.4% ± 2.3%). When CO2 production was assessed per day, the overnight-slope method showed an average difference of 9.4% ± 4.5% to indirect calorimetry. The overnight-slope method resulted in a more accurate estimation of CO2 production and EE compared with the plateau or slope-intercept method over a 5-d period in high physical activity conditions. Day-to-day determination of EE using the overnight-slope method was more accurate than diet recall and several standard prediction equations in athletes.

Reduced adaptive thermogenesis during acute protein-imbalanced overfeeding is a metabolic hallmark of the human thrifty phenotype

The human thrifty phenotype is characterized by a greater decrease in 24-h energy expenditure (24EE) during fasting due to relatively higher eucaloric 24EE in sedentary conditions, both of which are indicative of greater propensity to weight gain. Thriftiness is also associated with a smaller increase in 24EE (i.e., reduced adaptive thermogenesis) during overfeeding. We investigated whether short-term measures of adaptive thermogenesis during overfeeding with low/normal/high protein content characterize thriftiness. In this secondary cross-sectional analysis of a single-arm crossover study, 24EE was measured using whole-room indirect calorimetry during energy balance, fasting, and different overfeeding conditions (low/3% protein, high/30% protein, and 3 normal/20% protein diets) with 200% of eucaloric requirements in 77 healthy individuals [63 men; BMI (in kg/m2): 26.4±4.3; body fat by DXA: 27.7%±9.4%, mean±SD] with normal glucose regulation. Relations between the 24EE during energy balance (adjusted for body composition) and 24EE during each overfeeding diet were analyzed using separate linear regression models. Participants were arbitrarily categorized as thrifty/spendthrift based on the median value (-177kcal/d) of the difference in 24EE between fasting and energy balance conditions. Differences in 24EE during low/high-protein overfeeding diets (regression line slope=0.76 and 0.68, respectively, both P<0.05 compared with slope=1) but not during the normal-protein overfeeding diets (all P>0.05 compared with slope=1) were dependent on baseline 24EE during energy balance. Specifically, individuals with higher eucaloric 24EE (thriftier phenotype) showed smaller increases in 24EE during protein-imbalanced overfeeding. Analyzed by group, thrifty individuals had smaller increases in 24EE by 42 and 237kcal/d during low- and high-protein overfeeding, respectively, compared with spendthrift individuals who showed greater increases in 24EE by 100 and 302kcal/d (P≤0.03 compared with thrifty group). During acute overfeeding conditions with low/high-protein content, thrifty participants have limited capacity to increase 24EE, indicating that impaired adaptive thermogenesis during protein-imbalanced diets further characterizes the thrifty phenotype and its susceptibility to weight gain. This trial was registered at clinicalTrials.gov as NCT00523627.

Metabolic flexibility during sleep

Known as metabolic flexibility, oxidized substrate is selected in response to changes in the nutritional state. Sleep imposes an extended duration of fasting, and oxidized substrates during sleep were assumed to progressively shift from carbohydrate to fat, thereby gradually decreasing the respiratory quotient (RQ). Contrary to this assumption, whole-room indirect calorimetry with improved time resolution revealed that RQ re-ascended prior to awakening, and nadir of RQ in non-obese young adults occurred earlier in women than men after bedtime. The transient decrease in RQ during sleep was blunted in metabolically inflexible men with smaller amplitude of diurnal rhythm in RQ. Similarly, the effect of 10 years difference in age on RQ became significant during sleep; the decrease in RQ during sleep was blunted in older subjects. Inter-individual difference in RQ become apparent during sleep, and it might serve as a window to gain insight into the early-stage pathogenesis of metabolic inflexibility.

Twenty-four hour assessments of substrate oxidation reveal differences in metabolic flexibility in type 2 diabetes that are improved with aerobic training.

The aim of this study was to assess metabolic flexibility (MetFlex) in participants with type 2 diabetes within the physiologically relevant conditions of sleeping, the post-absorptive (fasting) state and during meals using 24h whole-room indirect calorimetry (WRIC) and to determine the impact of aerobic training on these novel features of MetFlex. Normal-weight, active healthy individuals (active; n = 9), obese individuals without type 2 diabetes (ND; n = 9) and obese individuals with type 2 diabetes (n = 23) completed baseline metabolic assessments. The type 2 diabetes group underwent a 10week supervised aerobic training intervention and repeated the metabolic assessments. MetFlex was assessed by indirect calorimetry in response to insulin infusion and during a 24h period in a whole-room indirect calorimeter. Indices of MetFlex evaluated by WRIC included mean RQ and RQ kinetic responses after ingesting a standard high-carbohydrate breakfast (RQBF) and sleep RQ (RQsleep). Muscle mitochondrial energetics were assessed in the vastus lateralis muscle in vivo and ex vivo using 31P-magnetic resonance spectroscopy and high-resolution respirometry, respectively. The three groups had significantly different RQsleep values (active 0.823 ± 0.04, ND 0.860 ± 0.01, type 2 diabetes 0.842 ± 0.03; p < 0.05). The active group had significantly faster RQBF and more stable RQsleep responses than the ND and type 2 diabetes groups, as demonstrated by steeper and flatter slopes, respectively. Following the training intervention, the type 2 diabetes group displayed significantly increased RQBF slope. Several indices of RQ kinetics had significant associations with in vivo and ex vivo muscle mitochondrial capacities. Twenty-four hour WRIC revealed that physiological RQ responses exemplify differences in MetFlex across a spectrum of metabolic health and correlated with skeletal muscle mitochondrial energetics. Defects in certain features of MetFlex were improved with aerobic training, emphasising the need to assess multiple aspects of MetFlex and disentangle insulin resistance from MetFlex in type 2 diabetes. ClinicalTrials.gov NCT01911104. This study was funded by the ADA (grant no. 7-13-JF-53).

Reliability of measurements of energy expenditure and substrate oxidation using whole-room indirect calorimetry.

This analysis aimed to measure the intraparticipant reliability-the intraclass correlation coefficient-of all the components of daily energy expenditure (EE) (24-hour EE, sleep EE, resting EE, basal EE, and thermic effect of food) over a period of 3 consecutive days in 35 study participants. The components of daily EE and substrate use (respiratory exchange ratio) were measured over 3 consecutive days before and after a 3-week 1,000-kcal/d caloric restriction/weight-loss intervention. There was a high degree of reliability for sleep EE (96.8%), 24-hour EE (97.8%), basal EE (90.6%), and resting EE (93.2%) during the run-in period. The intraclass correlation coefficient for the follow-up period after weight loss (3.67 ± 1.10 kg) remained high for sleep EE (95.6%), 24-hour EE (100%), basal EE (96.1%), and resting EE (92.5%). The minimal detectable differences in EE were reduced by 30% for both 24-hour EE and sleep EE when comparing 2 days versus 1 day spent in the whole-room indirect calorimeter. The reliability of the daily components of EE is very high both prior to and after a weight-loss intervention. We here provide instrumental data for investigators to adequately power studies investigating energy metabolism using whole-room indirect calorimetry.

Metabolic Characterization of Meat, Fish, and Soda Intake in Males: Secondary Results from a Randomized Inpatient Pilot Study.

This study aimed to evaluate whether a 12-week, weight-maintaining, macronutrient-stable dietary intervention that varies only by meat, fish, or soda consumption alters 24-hour energy expenditure (24hrEE) and substrate oxidation. Healthy males were recruited to participate in a 12-week inpatient study and were randomized to a weight-maintaining dietary intervention that contained varying combinations of meat (0% or 19%), fish (0% or 6%), or soda (0% or 14%) in a factorial design. Macronutrient composition across dietary intervention groups was as follows: 50% of energy from carbohydrates, 30% of energy from fat, and 20% of energy from protein. Whole-room indirect calorimetry at baseline and week 12 were used to measure 24hrEE and substrate oxidation. Twenty-six males (mean [SEM], age: 46.6 [10.4] years; BMI: 26.9 [4.1] kg/m2 ) completed all measurements. Fish consumption resulted in higher 24hrEE by 126 (55) kcal/d compared with no fish consumption (P = 0.03), whereas 24hrEE for soda consumption was 132 (56) kcal/d (P = 0.03) lower. Approximately 80% of the decrease in 24hrEE with soda consumption was due to lower awake-inactive energy expenditure (EE; P = 0.001). No specific EE component accounted for the differences observed with fish consumption. The data indicate that dietary sources of protein and carbohydrates appear to influence 24hrEE and inactive EE.

Metabolic Flexibility During Sleep

SummaryKnown as metabolic flexibility, oxidized substrate is selected in response to changes in the nutritional state. Sleep imposes an extended duration of fasting, and oxidized substrates during sleep were assumed to progressively shift from carbohydrate to fat, thereby gradually decreasing the respiratory quotient (RQ). Contrary to this assumption, whole-room indirect calorimetry with improved time resolution revealed that RQ re-ascended prior to awakening, and nadir of RQ in non-obese young adults occurred earlier in women than men after bedtime. The transient decrease in RQ during sleep was blunted in metabolically inflexible men with smaller amplitude of diurnal rhythm in RQ. Similarly, the effect of 10 years difference in age on RQ became significant during sleep; the decrease in RQ during sleep was blunted in older subjects. Inter-individual difference in RQ become apparent during sleep, and it might serve as a window to gain insight into the early-stage pathogenesis of metabolic inflexibility.

Sulfur amino acid restriction, energy metabolism and obesity: a study protocol of an 8-week randomized controlled dietary intervention with whole foods and amino acid supplements

BackgroundDietary sulfur amino acid (SAA) restriction is an established animal model for increasing lifespan and improving metabolic health. Data from human studies are limited. In the study outlined in this protocol, we will evaluate if dietary SAA restriction can reduce body weight and improve resting energy expenditure (REE) and parameters related to metabolic health.Method/designMen and women (calculated sample size = 60), aged 18–45 years, with body mass index of 27–35 kg/m2 will be included in a double-blind 8-week dietary intervention study. The participants will be randomized in a 1:1 manner to a diet with either low or high SAA. Both groups will receive an equal base diet consisting of low-SAA plant-based whole foods and an amino acid supplement free of SAA. Contrasting SAA contents will be achieved using capsules with or without methionine and cysteine (SAAhigh, total diet SAA ~ 50–60 mg/kg body weight/day; SAAlow, total diet SAA ~ 15–25 mg/kg body weight/day). The primary outcome is body weight change. Data and material collection will also include body composition (dual X-ray absorptiometry), resting energy expenditure (whole-room indirect calorimetry) and samples of blood, urine, feces and adipose tissue at baseline, at 4 weeks and at study completion. Measures will be taken to promote and monitor diet adherence. Data will be analyzed using linear mixed model regression to account for the repeated measures design and within-subject correlation.DiscussionThe strength of this study is the randomized double-blind design. A limitation is the restrictive nature of the diet which may lead to poor compliance. If this study reveals a beneficial effect of the SAAlow diet on body composition and metabolic health, it opens up for new strategies for prevention and treatment of overweight, obesity and its associated disorders.Trial registration ClinicalTrials.gov: NCT04701346, Registration date: January 8th, 2021

Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans.

ObjectiveEating earlier in the daytime to align with circadian rhythms in metabolism enhances weight loss. However, it is unknown whether these benefits are mediated through increased energy expenditure or decreased food intake. We therefore performed the first randomized trial to determine how meal timing affects 24-hour energy metabolism when food intake and meal frequency are matched.MethodsEleven overweight adults practiced both early time-restricted feeding (eTRF; eating from 8 am-2 pm) and a control schedule (eating from 8 am-8 pm) each for four days. On the fourth day, 24-hour energy expenditure and substrate oxidation were measured by whole-room calorimetry, in conjunction with appetite and metabolic hormones.ResultseTRF did not affect 24-hour energy expenditure (Δ=10±16 kcal/day; p=0.55). Despite the longer daily fast (intermittent fasting), eTRF decreased mean ghrelin levels by 32±10 pg/ml (p=0.006), made hunger more even-keeled (p=0.006), and tended to increase fullness (p=0.06-0.10) and decrease the desire to eat (p=0.08). eTRF also increased metabolic flexibility (p=0.0006) and decreased the 24-hour non-protein respiratory quotient (Δ=−0.021±0.010; p=0.05).ConclusionsMeal timing interventions facilitate weight loss primarily by decreasing appetite rather than by increasing energy expenditure. eTRF may also increase fat loss by increasing fat oxidation.

Hydration biomarkers and copeptin: relationship with ad libitum energy intake, energy expenditure, and metabolic fuel selection.

Background/ObjectiveEvidence from non-human species indicate that hydration and arginine vasopressin (AVP) influence fuel selection, energy expenditure (EE), and food intake, but these relationships are unclear in humans. We sought to assess whether hydration biomarkers [24-h urine volume (UVol) and urine urea nitrogen concentration (UUN)] and copeptin (a surrogate for AVP) are associated with 24-h EE, respiratory quotient (RQ), and daily energy intake (DEI).Subjects/MethodsIn a secondary analysis of collected data, we selected healthy adults (Group 1, n = 177) who had 24-h whole-room indirect calorimetry measurements in energy balance with 24-h urine collection and fasting copeptin measurements (n=117), followed by 3 days ad libitum food intake. A separate group (Group 2, n=284) with hydration markers and calorimetry measurements was also studied. The main outcome measures were 24-h RQ, 24-h EE, DEI, substrate oxidation.ResultsIn Group 1, lower 24-h UVol and higher 24-h UUN, indicating lower hydration, were correlated with lower 24-h RQ (r = 0.35, p <0.0001, and r = −0.29, p = 0.0001, respectively; results similar in Group 2) and predicted subsequent reduced DEI (r = 0.20, p = 0.01, and r = −0.27, p = 0.0003, respectively), adjusted for confounders. Copeptin was independently associated with 24-h lipid oxidation (r = −0.23, p = 0.01). In Group 2, lower hydration was associated with reduced 24-h EE (24-h UVol: r = 0.29, p <0.0001; 24-h UUN: r = −0.25, p <0.0001).ConclusionsHydration biomarkers were associated with metabolic differences characterized by altered food intake, fuel selection, and possibly EE. Independently, copeptin was associated with higher lipid oxidation.

Norepinephrine and T4 Are Predictors of Fat Mass Gain in Humans With Cold-Induced Brown Adipose Tissue Activation.

In healthy adults with detectable cold-induced brown adipose tissue activation (CIBA), the relationships between sympathetic nervous system (SNS) or thyroid activity during energy balance (EBL) with CIBA and body composition change are undetermined. To investigate the relationships between CIBA and thermoneutral catecholamines and thyroid hormones measured during EBL and to determine if CIBA, catecholamines, or thyroid hormones predict body composition changes. Twelve healthy volunteers (seven male and five female) with positive CIBA [>2 standardized uptake value (g/mL)] had 24-hour energy expenditure (24hEE) assessed during EBL via whole-room indirect calorimetry while residing on a clinical research unit. Positron emission tomography/computed tomography scans were performed after exposure to 16°C for 2 hours to quantify CIBA. CIBA, 24hEE during EBL, and thermoneutrality with concomitant measurement of urinary catecholamines and plasma free T3 and free T4. Body composition at baseline and 6 months by dual-energy X-ray absorptiometry. Lower urinary norepinephrine and free T4 were associated with higher CIBA (r = -0.65, P = 0.03; and r = -0.75, P < 0.01, respectively), but CIBA was not associated with 24hEE at thermoneutrality (P = 0.77). Lower CIBA (β = -3.5 kg/standardized uptake value; P < 0.01) predicted fat mass gain, whereas higher urinary norepinephrine and free T4 predicted future fat mass gain at 6 months (β = 3.0 kg per twofold difference in norepinephrine, P = 0.03; and β = 1.2 kg per 0.1-ng/dL difference in free T4, P = 0.03, respectively). Lower SNS and free thyroid measurements at baseline indicate a greater capacity for CIBA, which may be predictive against fat mass gain.

Response of skeletal muscle UCP2-expression during metabolic adaptation to caloric restriction.

Spendthrift vs. thrifty individuals expend more energy and experience greater weight loss during caloric restriction (CR). Adaptive mechanisms in skeletal muscle, adipose tissue, and on hormone level modulate energy expenditure (EE) during weight loss. Metabolic mechanisms underlying the variability in EE during CR are unclear. The present study explored whether during long-term CR (i) gene expression changes in skeletal muscle and adipose tissue relate with the individual EE response and weight loss, and (ii) altered catecholamine and FGF21-concentrations are associated with measures of metabolic adaptation. In a 10-week inpatient study, 24-h EE was measured before and after 6 weeks of 50% CR in 12 subjects using whole-room indirect calorimetry. Weight loss was assessed and repeated hormone measurements performed. Muscle and adipose tissue biopsies were taken before and after CR, and gene expression was assessed (RNA-Seq). Genes showing the most significant changes after CR were tested for association with EE and followed-up for further association with metabolic measures in a separate phenotyping study (n = 103). Muscle UCP2 showed the strongest change after CR (log2-fold change = -1.57, false discovery rate = 0.10) and was considered the best gene for exploration of metabolic adaptive processes. A greater decrease in UCP2-expression was associated with less weight loss (P = 0.03, r = 0.77) and relatively lower 24-h EE after CR (P = 0.001, r = -0.96). Post-CR changes in FGF21-plasma concentrations correlated with UCP2-expression change (P = 0.02, r = -0.89) and weight loss (P = 0.003, r = -0.83). In a separate metabolic phenotyping study, muscle UCP2-expression correlated with respiratory quotient and macronutrient oxidation. In adipose tissue, no candidate genes for metabolic exploration were found. Changes in muscle UCP2-expression reflect an inter-individual metabolic response to long-term CR and may influence EE and weight loss via modulation of substrate oxidation.

A High-Fat Compared with a High-Carbohydrate Breakfast Enhances 24-Hour Fat Oxidation in Older Adults

BackgroundThe ability to oxidize fat is associated with a lower risk of chronic metabolic disease. Preclinical data in mice showed that a high-fat “breakfast” increased 24-h fat oxidation relative to a high-carbohydrate breakfast. ObjectiveThe objectives of this study were to determine whether the timing of macronutrient intake in humans affects daily fuel utilization and to examine associations between fuel utilization and metabolic indexes. MethodsParticipants were 29 healthy sedentary men and women (aged 55–75 y) with a body mass index (kg/m2) between 25 and 35. Participants were randomly assigned to receive either a high-fat breakfast (FB; 35% carbohydrate, 20% protein, 45% fat; n = 13) or a high-carbohydrate breakfast (CB; 60% carbohydrate, 20% protein, 20% fat; n = 16) for 4 wk while consuming a “neutral” lunch and dinner. Twenty-four-hour and postprandial respiratory quotients (RQs) were measured by whole-room indirect calorimetry. Insulin and glucose measures including insulin sensitivity were determined by an oral-glucose-tolerance test. Measures were taken at baseline and after the 4-wk intervention. Group-by-time interactions were determined by 2-factor repeated-measures mixed-model ANOVA. Pearson’s correlation analyses were used to determine associations of 24-h RQs with metabolic measures after the intervention. ResultsThere was a significant group-by-time interaction for change in the 24-h RQ [FB (mean ± SD): 0.88 ± 0.02 to 0.86 ± 0.02; CB: 0.88 ± 0.02 for both; P < 0.05], breakfast RQ (FB: 0.88 ± 0.03 to 0.86 ± 0.03; CB: 0.89 ± 0.02 to 0.90 ± 0.02; P < 0.01), and lunch RQ (FB: 0.089 ± 0.03 to 0.85 ± 0.03; CB: 0.89 ± 0.03 for both; P < 0.01). In the CB group at follow-up, 24-h RQ was positively associated with fasting glucose (r = 0.66, P < 0.05), glucose area under the curve (AUC) (r = 0.51, P < 0.05), and insulin AUC (r = 0.52, P < 0.05) and inversely associated with insulin sensitivity (r = –0.51, P < 0.05). ConclusionsThe macronutrient composition of breakfast affects substrate utilization throughout the day in older adults. The consumption of a high-fat, lower-carbohydrate breakfast may reduce the risk of metabolic disease. This trial was registered at www.clinicaltrials.gov as NCT03164200.

Oxygen Consumption during Viniyoga Practice in Adults.

Context:The purpose of this study was to measure the oxygen consumption (V̇O2) during Viniyoga yoga movements (asanas) and to compare V̇O2 walking among adults.Methods:Yoga practitioners (n = 10) were recruited to measure V̇O2 while at rest (30 min), practicing yoga (16 movements with different variations), and treadmill walking at 2 mph (10 min) and 3 mph (10 min). V̇O2 was measured using a whole-room indirect calorimetry. Each yoga movement was categorized by body orientation as standing, lying, and sitting. The differences in V̇O2 between yoga and walking were examined using Pearson's correlations. Differences in V̇O2 between poses (standing, sitting, and lying) were examined using linear regression models. V̇O2.Results:Mean yoga-V̇O2 for the entire yoga session was 3.7 (standard deviation [SD] 0.43, range: 4.4–8.9) ml/kg/min. Yoga-V̇O2 varied by body orientation: standing = 7.5 (SD = 1.5) ml/kg/min, lying = 5.3 (SD = 1.0) ml/kg/min, and sitting = 5.4 (SD = 1.1) ml/kg/min. After adjusting for body mass, frequency of yoga practice, and resting energy expenditure, female gender was negatively associated with mean yoga V̇O2 for standing (B = −112.19, P < 0.05), lying (B = −141.87, P < 0.05), and sitting (B = −129.96, P < 0.05). Mean V̇O2 for walking 2 mph was comparable with sitting (r = 0.836, P < 0.05) and lying (r = 0.735, P < 0.05) whereas walking at 3 mph was comparable with standing (r = 0.718, P < 0.05) and sitting (r = 0.760, P < 0.05).Conclusion:We conclude that V̇O2 during yoga practice is comparable to V̇O2 during slow treadmill walking and may vary based on gender and body orientation.

Daytime bright light exposure, metabolism, and individual differences in wake and sleep energy expenditure during circadian entrainment and misalignment

Daytime light exposure has been reported to impact or have no influence on energy metabolism in humans. Further, whether inter-individual differences in wake, sleep, 24 h energy expenditure, and RQ during circadian entrainment and circadian misalignment are stable across repeated 24 h assessments is largely unknown. We present data from two studies: Study 1 of 15 participants (7 females) exposed to three light exposure conditions: continuous typical room ~100 lx warm white light, continuous ~750 lx warm white light, and alternating hourly ~750 lx warm white and blue-enriched white light on three separate days in a randomized order; and Study 2 of 14 participants (8 females) during circadian misalignment induced by a simulated night shift protocol. Participants were healthy, free of medical disorders, medications, and illicit drugs. Participants maintained a consistent 8 h per night sleep schedule for one week as an outpatient prior to the study verified by wrist actigraphy, sleep diaries, and call-ins to a time stamped recorder. Participants consumed an outpatient energy balance research diet for three days prior to the study. The inpatient protocol for both studies consisted of an initial sleep disorder screening night. For study 1, this was followed by three standard days with 16 h scheduled wakefulness and 8 h scheduled nighttime sleep. For Study 2, it was followed by 16 h scheduled wake and 8 h scheduled sleep at habitual bedtime followed by three night shifts with 8 h scheduled daytime sleep. Energy expenditure was measured using whole-room indirect calorimetry. Constant posture bedrest conditions were maintained to control for energy expenditure associated with activity and the baseline energy balance diet was continued with the same exact meals across days to control for thermic effects of food. No significant impact of light exposure was observed on metabolic outcomes in response to daytime light exposure. Inter-individual variability in energy expenditure was systematic and ranged from substantial to almost perfect consistency during both nighttime sleep and circadian misalignment. Findings show robust and stable trait-like individual differences in whole body 24 h, waking, and sleep energy expenditure, 24 h respiratory quotient—an index of a fat and carbohydrate oxidation—during repeated assessments under entrained conditions, and also in 24 h and sleep energy expenditure during repeated days of circadian misalignment.

Measurement Of Daily Energy Expenditure In Humans Using A Body-worn Calorimter

PURPOSE: Previous approaches using body-worn devices to measure free-living daily EE in humans using direct calorimetry have been limited by the inability to accurately measure evaporative heat loss. The Personal Calorie Meter (PCM) is a device that uses a heat flow gauge embedded in a permeable membrane, permitting the measurement of both dry and evaporative heat loss. Total heat flux and estimated body surface area are then used to estimate minute by minute EE. In this ongoing study, we are comparing daily EE measured using the PCM with simultaneous measurements using whole-room indirect calorimetry (WRC). METHODS: Subjects were studied on two separate days under low and high physical activity levels (PAL, ~1.4 and 1.7 x resting metabolic rate, respectively) in the WRC. During the low PAL condition, subjects performed 20 minutes of various housecleaning activities. During the high PAL condition, subjects performed 30 minutes of walking on a treadmill, 30 minutes of stationary cycling, and resistance exercises using dumbbells. Daytime EE was calculated as the total EE from the time the subject entered the WRC until bedtime. RESULTS: 14 subjects (10 F/4 M, 44±18 yrs., body mass index=26±6 kg.m2, mean±SD) have completed at least one study visit in the room calorimeter. During the low PAL condition (N=11), average daytime EE measured by the PCM (1369±220 kcal, mean±SD) did not differ from WRC (1304±757 kcal), but the range of intra-individual differences was large (-899 to +452 kcal). Five measurements were within ±150 kcal, and the minute-to-minute values corresponded closely in these cases. During the high PAL condition (N=9), average daytime EE measured by the PCM (1834±344 kcal) did not differ from WRC (1880±757 kcal), but there was a wider range of intra-individual differences than during the low PAL condition (-1188 to +1075 kcal). CONCLUSION: These preliminary data demonstrate the feasibility of measuring EE in humans using portable direct calorimetry. Further studies and refinements are needed to improve the accuracy of the PCM on an individual level.

Characterization of wrist-wearable activity measurement using whole body calorimetry in semi-free living conditions.

Physical activity (PA) is a significant factor in a number of health conditions and monitoring PA can play a significant role in the treatment of, or research into, these conditions. For longitudinal monitoring of PA, unobtrusive devices are often used and there is a need for the development of energy expenditure (EE) estimation techniques from single-device systems. This paper presents an experiment designed to characterize the relationship between a previously described technique, the activity score (AS) and EE obtained from whole-room indirect calorimetry. The study used 8 participants over a 24-hr period with interspersed exercise periods to observe physical movement with wearable devices and EE in 5 minute epochs. Results show that AS and EE are correlated with a Spearman's rank correlation coefficient of 0.775 with p <; 0.001.

Postprandial thermogenesis and substrate oxidation are unaffected by sleep restriction

Background/ObjectivesThe extent to which alterations in energy expenditure (EE) in response to sleep restriction contribute to the short sleep-obesity relationship is not clearly defined. Short sleep may induce changes in resting metabolic rate (RMR), thermic effect of food (TEF), and postprandial substrate oxidation.Subjects/MethodsTen females (age and BMI: 22-43 y and 23.4-28 kg/m2) completed a randomized, crossover study assessing the effects of short (4 h/night) and habitual (8 h/night) sleep duration on fasting and postprandial RMR and respiratory quotient (RQ). Measurements were taken after 3 nights using whole-room indirect calorimetry. The TEF was assessed over a 6-h period following consumption of a high-fat liquid meal.ResultsShort vs. habitual sleep did not affect RMR (1.01 ± 0.05 and 0.97 ± 0.04 kcal/min; p=0.23). Fasting RQ was significantly lower after short vs. habitual sleep (0.84 ± 0.01 and 0.88 ± 0.01; p=0.028). Postprandial EE (short: 1.13 ± 0.04 and habitual: 1.10 ± 0.04, p=0.09) and RQ (short: 0.88 ± 0.01 and habitual: 0.88 ± 0.01, p=0.50) after the high-fat meal were not different between conditions. TEF was similar between conditions (0.24 ± 0.02 kcal/min in both; p=0.98), as was the ~6-h incremental area under the curve (1.16 ± 0.10 and 1.17 ± 0.09 kcal/min x 356 min after short and habitual sleep, respectively; p=0.92).ConclusionsCurrent findings observed in non-obese healthy premenopausal women do not support the hypothesis that alterations in TEF and postprandial substrate oxidation are major contributors to the higher rate of obesity observed in short sleepers. In exploring a role of sleep duration on EE, research should focus on potential alterations in physical activity to explain the increased obesity risk in short sleepers.