Effect of inpatient versus outpatient measurement protocol on resting metabolic rate and respiratory exchange ratio

No Difference in Young Adult Athletes’ Resting Energy Expenditure When Measured Under Inpatient or Outpatient Conditions

Low energy availability can place athletes at increased risk of injury and illness and can be detected by a lower metabolic rate. The lowest metabolic rate is captured at the bedside, after an overnight fast and termed inpatient resting energy expenditure (REE). Measurements done in a laboratory with a shorter overnight fast are termed outpatient REE. Although important to know what the lowest energy expenditure, a bedside measure and/or 12-hr fast is not always practical or logistically possible particularly when you take into account an athlete’s training schedule. The aim of this investigation was to compare a bedside measure of resting metabolism with a laboratory measure in athletes following an 8-hr fast. Thirty-two athletes (24 females and eight males) underwent measures of resting metabolism using indirect calorimetry once at their bedside (inpatient) and once in a simulated laboratory setting (outpatient). Paired t test was used to compare the mean ± SD differences between the two protocols. Inpatient REE was 7,302 ± 1,272 kJ/day and outpatient REE was 7,216 ± 1,116 kJ/day (p = .448). Thirteen participants repeated the outpatient protocol and 17 repeated the inpatient protocol to assess the day-to-day variation. Reliability was assessed using the intraclass correlation coefficient and typical error. The inpatient-protocol variability was 96% with a typical error of 336.2 kJ/day. For the outpatient protocol, the intraclass correlation coefficient and typical error were 87% and 477.6 kJ/day, respectively. Results indicate no difference in REE when measured under inpatient and outpatient conditions; however, the inpatient protocol has greater reliability.

How long does it take to achieve steady state for an accurate assessment of resting VO₂ in healthy men?

The time necessary to obtain a steady state for an accurate and reliable assessment of resting [Formula: see text] remains unclear and was the purpose of this study. Thirty healthy men, aged 17-28 years, visited the laboratory twice for the assessment of resting [Formula: see text], which was assessed as follows: (a) 24 h abstention from physical exercise, alcohol, soft drinks and caffeine, (b) fasting for at least 8 h, (c) an acclimation period of 10 min, and (d) 60 min assessment in a supine position. Resting [Formula: see text] significantly changed during the 60 min (F = 37.4, P < 0.001), exhibiting a monoexponential decrease before reaching an asymptote. Post hoc pairwise comparisons showed that significant differences existed between consecutive means until the 30 min time point, after which there were no significant differences. The [Formula: see text] response across trials exhibited high test-retest reliability, with within-subject coefficients of variations at each time point ranging from 2.8 to 7.0 % and intraclass correlation coefficients ranging from 0.90 to 0.99. The reliability was higher from the 25 min time point onwards. Based on these findings, the following recommendations are made to promote accurate assessment of resting [Formula: see text]: (a) initiate the resting [Formula: see text] measurement with 10 min of acclimation to the assessment apparatus, (b) determine resting [Formula: see text] for a minimum of 30 min, until an apparent [Formula: see text] steady state has been achieved; and (c) determine resting [Formula: see text] for a further 5 min, with the average of this last 5 min of data being regarding as the resting [Formula: see text].

Resting metabolic rate in old-old women with and without frailty: variability and estimation of energy requirements

OBJECTIVES

To measure resting metabolic rate (RMR) in old-old adults living in the community and examine the association between measured RMR and frailty status and compare it with expected RMR generated by a predictive equation.

DESIGN

Physiological substudy conducted as a home visit within an observational cohort study.

SETTING

Baltimore City and County, Maryland.

PARTICIPANTS

Seventy-seven women aged 83 to 93 enrolled in the Women's Health and Aging Study II.

MEASUREMENTS

Resting metabolic rate with indirect calorimetry, frailty status, fat-free mass, ambient and body temperature, expected RMR according to the Mifflin-St. Jeor equation.

RESULTS

Average RMR was 1,119 ± 205 kcal/d (range 595-1,560 kcal/d). Agreement between observed and expected RMR was biased and poor (between-subject coefficient of variation 38.0%, 95% confidence interval = 35.1-40.8). Variability of RMR was greater in frail individuals (heteroscedasticity F-test P = .02). Low and high RMR were associated with being frail (odds ratio 5.4, P = .04) and slower self-selected walking speed (P < .001) after adjustment for covariates.

CONCLUSION

Equations to predict RMR that are not validated in old-old adults appear to correlate poorly with measured RMR. RMR is highly variable in old-old women, with deviations from the mean predicting clinical frailty. These exploratory findings suggest a pathway to clinical frailty through high or low RMR.

Effect of exercise intensity, duration and mode on post-exercise oxygen consumption

In the recovery period after exercise there is an increase in oxygen uptake termed the 'excess post-exercise oxygen consumption' (EPOC), consisting of a rapid and a prolonged component. While some studies have shown that EPOC may last for several hours after exercise, others have concluded that EPOC is transient and minimal. The conflicting results may be resolved if differences in exercise intensity and duration are considered, since this may affect the metabolic processes underlying EPOC. Accordingly, the absence of a sustained EPOC after exercise seems to be a consistent finding in studies with low exercise intensity and/or duration. The magnitude of EPOC after aerobic exercise clearly depends on both the duration and intensity of exercise. A curvilinear relationship between the magnitude of EPOC and the intensity of the exercise bout has been found, whereas the relationship between exercise duration and EPOC magnitude appears to be more linear, especially at higher intensities. Differences in exercise mode may potentially contribute to the discrepant findings of EPOC magnitude and duration. Studies with sufficient exercise challenges are needed to determine whether various aerobic exercise modes affect EPOC differently. The relationships between the intensity and duration of resistance exercise and the magnitude and duration of EPOC have not been determined, but a more prolonged and substantial EPOC has been found after hard- versus moderate-resistance exercise. Thus, the intensity of resistance exercise seems to be of importance for EPOC. Lastly, training status and sex may also potentially influence EPOC magnitude, but this may be problematic to determine. Still, it appears that trained individuals have a more rapid return of post-exercise metabolism to resting levels after exercising at either the same relative or absolute work rate; however, studies after more strenuous exercise bouts are needed. It is not determined if there is a sex effect on EPOC. Finally, while some of the mechanisms underlying the more rapid EPOC are well known (replenishment of oxygen stores, adenosine triphosphate/creatine phosphate resynthesis, lactate removal, and increased body temperature, circulation and ventilation), less is known about the mechanisms underlying the prolonged EPOC component. A sustained increased circulation, ventilation and body temperature may contribute, but the cost of this is low. An increased rate of triglyceride/fatty acid cycling and a shift from carbohydrate to fat as substrate source are of importance for the prolonged EPOC component after exhaustive aerobic exercise. Little is known about the mechanisms underlying EPOC after resistance exercise.

Resting energy expenditures in Asian women measured by indirect calorimetry are lower than expenditures calculated from prediction equations

OBJECTIVE

Measured resting energy expenditure (REE) and REEs calculated using the Harris-Benedict equation, Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) equations (FAO equations), and the Liu equation were compared in Asian women.

DESIGN

REEs were measured using indirect calorimetry in the morning after an overnight fast and compared with REEs calculated using the Harris-Benedict equation, the FAO equations, and the Liu equation. Height, weight, and 3-day diet records were also obtained.

SUBJECTS

Thirty-six healthy, free-living Asian women aged 19 to 52 years and living in the United States were recruited from Washington State University, Pullman, and completed the study.

STATISTICAL ANALYSES

Paired t tests, stepwise regression, one-way analysis of variance, and Pearson correlation coefficients were used for the statistical analyses. Significance was set at P < or = .05.

RESULTS

A significant correlation was found between measured REE and REE derived from the Harris-Benedict equation (R = 0.67, P < .0001), the FAO equations (R = 0.70, P < .0001), and the Liu equation (R = 0.70, P < .0001). However, measured REE was significantly lower than REE calculated using the Harris-Benedict and FAO equations by 8.5% (P < .001) and 5.4% (P < .01), respectively. No significant difference was noted between measured REE and REE derived from the Liu equation.

APPLICATIONS

Caution must be taken when predicting REE of Asian women using the Harris-Benedict equation or the FAO equation. Indirect calorimetry or an equation specific to Asians, such as the Liu equation, is recommended when an accurate estimate is necessary.

Influence of moderate daily wine consumption on body weight regulation and metabolism in healthy free-living males

OBJECTIVE

Although previous studies have clearly demonstrated that energy from alcohol may not be efficiently utilized to maintain body weight when it comprises 20% or more of the daily caloric intake, there is considerable debate regarding the influence of moderate alcohol consumption (< or = 5% of the total daily caloric intake) upon metabolism, substrate utilization and body weight regulation. Consequently, the objectives of this study were to determine whether moderate alcohol consumption could influence body weight via changes in substrate utilization, oxygen consumption or alterations in dietary macronutrient content.

METHODS

Fourteen male subjects (mean age = 32.1 years) participated in a 12-week, free-living, crossover trial in which they either drank red wine (270 ml; 13% v/v ethanol) daily for 6 weeks and then abstained for the next 6 weeks or vice-versa.

RESULTS

Whether wine was imbibed or not, no significant differences (p > 0.05) were demonstrated for any of the following variables: body weight, body fat percentage, skinfold thickness, resting metabolic rate, respiratory quotient, caloric intake, dietary macronutrient content, or fasting insulin or glucose concentrations.

CONCLUSIONS

In free-living subjects over a 6-week period, the addition of two glasses of red wine to the evening meal does not appear to influence any measured variable which may adversely affect body weight or promote the development of obesity during this time period.

Relationship between maximum aerobic power and resting metabolic rate in young adult women

The literature is inconclusive as to the chronic effect of aerobic exercise on resting metabolic rate (RMR), and furthermore there is a scarcity of data on young women. Thirty-four young women exhibiting a wide range of aerobic fitness [maximum aerobic power (VO2max) = 32.3-64.8 ml.kg-1.min-1] were accordingly measured for RMR by the Douglas bag method, treadmill VO2max, and fat-free mass (FFM) by using Siri's three-compartment model. The interclass correlation (n = 34) between RMR (kJ/h) and VO2max (ml.kg-1.min-1) was significant (r = 0.39, P < 0.05). However, this relationship lost statistical significance when RMR was indexed to FFM and when partial correlation analysis was used to control for FFM differences. Furthermore, multiple linear-regression analysis indicated that only FFM emerged as a significant predictor of RMR (kJ/h). When high- (n = 12) and low-fitness (n = 12) groups were extracted from the cohort on the basis of VO2max scores, independent t-tests revealed significant between-group differences (P < 0.05) for RMR (kJ.kg-1.h-1) and VO2max (ml.kg-1.min-1) but not for RMR (kJ/h), RMR (kJ.kg FFM-1.h-1), and FFM. Analysis of covariance of RMR (kJ/h) with FFM as the covariate also showed no significant difference (P = 0.56) between high- and low-fitness groups. Thus the results suggest that 1) FFM accounts for most of the differences in RMR between subjects of varying VO2max values and 2) the RMR per unit of FFM in young healthy women is unrelated to VO2max.

Postexercise energy expenditure in response to acute aerobic or resistive exercise

Postexercise energy metabolism was examined in male subjects age 22-35 years in response to three different treatments: a strenuous bout of resistive exercise (REx), a bout of stationary cycling (AEx) at 50% peak VO2, and a control condition (C) of quiet sitting. Resting metabolic rate (RMR) was measured the morning of and the morning following each condition. Recovery oxygen consumption (RcO2) was measured for 5 hr following each treatment. Total 5-hr RcO2 was higher for the REx treatment relative to both AEx and C, with the largest treatment differences occurring early during recovery. There were no large treatment differences in postexercise respiratory exchange ratio values, except for the first hour of recovery following REx. RMR measured 14.5 hr postexercise for the REx condition was significantly elevated compared to C. These results suggest that strenuous resistive exercise results in a greater excess postexercise oxygen consumption compared to steady-state endurance exercise of similar estimated energy cost.