Energy Expenditure and Physical Activity
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
- To determine the reproducibility or intra-individual variability of BMR after 3 repeated measurements, using an outpt protocol
- To study the effect of the within-machine variability
- To assess the inter-individual variability of BMR and explain differences between subjects by differences in physical characteristics.
Definitions
- Steady state: Not defined
- BMR: Equivalent to project’s definition of RMR.
Inclusion Criteria:
- Understand and give written consent
- Good health with absence of metabolic diseases:
- No use of medication that could have affected metabolic rate
- Weight stability during the last 6 mos (±3 kg)
- Not on any special diets or participating in exercise programmes.
Exclusion Criteria:
- Refusal to consent
- Not meeting inclusion criteria.
Description of Study Protocol:
- BMR measured 3 times at 2-week intervals; measurements were repeated at the same time and day of the week for each subject.
- Physical activity: Estimated 3 days before each measurement. Order of measures on day of BMR: BMR, est body weight; underwater weighing.
ANTHROPOMETRIC
- Ht measured? Yes
- Wt measured? Yes
- Fat-free mass measured? Underwater weighing; 3-compartment Siri.
CLINICAL:
- Monitored heart rate? Yes, through a polarized chest belt
- Body temperature? No
- Medications administered? Excluded.
Resting energy expenditure
- IC type: Omnical
- Equipment of Calibration: Yes
- Coefficient of variation using std gases: Yes
- Rest before measure (state length of time rested if available): 10 minutes
- Measurement length: Entire 45 mins; eliminated first 10 and last 15 mins
- Steady state: Eliminated last 15 mins due to restlessness at end of measure.
- Fasting length: Yes, 12 hours
- Exercise restrictions XX hr prior to test? Yes
- Room temp: 22-24 C
- No. of measures within the measurement period: 1
- Were some measures eliminated? Yes
- Were a set of measurements averaged? 15 one-minute measures
- Training of measurer? Not specified
- Subject training of measuring process? Trained of procedures.
DIETARY
- None.
Data Collection Summary:
Outcome(s) and other measures
- Measured REE [(VO2, l/min), VCO2 (l/min; ml/kg/min)
- Physical activity with a tri-axial accelerometer for movement
- Total body water (H2 dilution method)
- Independent variables: weight, height, age,and fat-free mass, fat mass.
Blinding used: No.
Description of Actual Data Sample:
- N=19 volunteers (8M 11F)
- Mean age, y: 23.6±7.5 SD.
Statistical tests
- Mean values and SD;
- One-way factor ANOVA for repeat measures; use of sex as a between-subject variable
- Coefficient of variation, mean differences between the measures and coefficient of correlation wer used to compare the BMR values between the three visits for each visit; The intra- and inter-variability of BMR measures uwere assess via multiple and simple liniear regression analyses, p values <0.05 were significant.
Summary of Results:
ANTHROPOMETRIC
Men | Mean (±SD) |
Age, y |
23±5 |
Wt, kg |
78.6±14.3 |
Ht, m |
1.86±0.1 |
Fat mass, kg |
14.4±5.9 |
Fat-free mass, kg |
64.3±10.3 |
Women |
|
Age, y |
24±9 |
Wt, kg |
61.7±7.2 |
Ht, m |
1.73±0.1 |
Fat mass, kg |
18.2±5.9 |
Fat-free mass, kg |
43.6±3.7 |
BMR COEFFICIENT OF VARIATION
- The mean intra-individual CV was 3.3±2.1 %
- Range, CV: 0.4-7.2%.
Kcal differences between the three measures
- 0.3±0.3 MJ /24 (72±72 kcals/d) between measure 1 and 2
- 0.2±0.2 MJ/24 hr (48±48 kcals/d) between measure 2 and 3
- 0.3±0.2 MJ/24 hr between measure 1 and 3 (72±48 kcals/d)
- The coefficient of correlation was 0.939 between measure 1 and 2;
- 0.918 between measure 1 and 3
- 0.980 between measure 2 and 3.
PHYSICAL ACTIVITY COEFFICIENT OF VARIATION
- The mean intra-individual CV for physical activity was 21±18% and it ranged from 0 to 65%.
- Differences between BMR could not be explained by differences in physical activity the day before testing or by changes in body mass.
INTER-INDIVIDUAL CV OF BMR MEASURES
- Mean inter-individual CV of BMR was 18.0±1.6. Most of this variation was explained by FFM differences between the subjects.
Author Conclusion:
As stated by the author in body of report:
- “Intra-individual CV was 3.3±2.1% with a range from 0.4 to 7.2% and similar results observed by others [studies in adults] (Fredrix et al. 1990).”
- “The present study quantified potential factors affecting the reproducibility of BMR values, including the habitual physical activity the day before and non-compliance to fasting ... and with-machine variability was larger than 7.5 ml/min for CO2 or 11 ml/min for (2. The correction for within machine variability reduced the CV from 5.7% to 5.2%.”
- “After exclusion of noncompliance measures, the CV decreased from 5.2 to 3.3%.”
- “No evidence is found for an important influence of the intra-individual variability of non-exercise activity on the reproducibility of BMR measurements.”
- “BMR measurements performed with a standard outpatient protocol results in highly reproducible BMR values; specifically, if corrected for non-compliance to the protocol (i.e., fasting) and for within-machine variability (>7.5 ml/min for CO2 or >11 ml/min for O2... the actual recommendation to refrain from exercise is sufficient to ensure accurate measures as well as weekly methanol calibration.”
Funding Source:
University/Hospital: | Maastricht University |
Reviewer Comments:
Strengths
- Provided discussion of IC measurement protocol
- Measured and discussed primary components that affect RMR: fasting, physical activity, FFM, machine reliability
- Measured every 2 weeks
- Proper use of statistics.
Generalizability/Weaknesses
- “Generalizable to nonbese and obese adult males and females."
- Generalizable to outpatient measurement protocols
- Unable to generalize to older and very old adults.
- Additional detail on “steady state” and quantifying rest longer than 10 minutes before 1st measure.
Quality Criteria Checklist: Primary Research
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Relevance Questions | |||
1. | Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) | Yes | |
2. | Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? | Yes | |
3. | Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? | Yes | |
4. | Is the intervention or procedure feasible? (NA for some epidemiological studies) | Yes | |
Validity Questions | |||
1. | Was the research question clearly stated? | Yes | |
1.1. | Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? | N/A | |
1.2. | Was (were) the outcome(s) [dependent variable(s)] clearly indicated? | N/A | |
1.3. | Were the target population and setting specified? | N/A | |
2. | Was the selection of study subjects/patients free from bias? | Yes | |
2.1. | Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? | N/A | |
2.2. | Were criteria applied equally to all study groups? | N/A | |
2.3. | Were health, demographics, and other characteristics of subjects described? | N/A | |
2.4. | Were the subjects/patients a representative sample of the relevant population? | N/A | |
3. | Were study groups comparable? | N/A | |
3.1. | Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) | N/A | |
3.2. | Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? | N/A | |
3.3. | Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) | N/A | |
3.4. | If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? | N/A | |
3.5. | If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) | N/A | |
3.6. | If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? | N/A | |
4. | Was method of handling withdrawals described? | No | |
4.1. | Were follow-up methods described and the same for all groups? | N/A | |
4.2. | Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) | N/A | |
4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | N/A | |
4.4. | Were reasons for withdrawals similar across groups? | N/A | |
4.5. | If diagnostic test, was decision to perform reference test not dependent on results of test under study? | N/A | |
5. | Was blinding used to prevent introduction of bias? | No | |
5.1. | In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? | N/A | |
5.2. | Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) | N/A | |
5.3. | In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? | N/A | |
5.4. | In case control study, was case definition explicit and case ascertainment not influenced by exposure status? | N/A | |
5.5. | In diagnostic study, were test results blinded to patient history and other test results? | N/A | |
6. | Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? | Yes | |
6.1. | In RCT or other intervention trial, were protocols described for all regimens studied? | N/A | |
6.2. | In observational study, were interventions, study settings, and clinicians/provider described? | N/A | |
6.3. | Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? | N/A | |
6.4. | Was the amount of exposure and, if relevant, subject/patient compliance measured? | N/A | |
6.5. | Were co-interventions (e.g., ancillary treatments, other therapies) described? | N/A | |
6.6. | Were extra or unplanned treatments described? | N/A | |
6.7. | Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? | N/A | |
6.8. | In diagnostic study, were details of test administration and replication sufficient? | N/A | |
7. | Were outcomes clearly defined and the measurements valid and reliable? | No | |
7.1. | Were primary and secondary endpoints described and relevant to the question? | N/A | |
7.2. | Were nutrition measures appropriate to question and outcomes of concern? | N/A | |
7.3. | Was the period of follow-up long enough for important outcome(s) to occur? | N/A | |
7.4. | Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? | N/A | |
7.5. | Was the measurement of effect at an appropriate level of precision? | N/A | |
7.6. | Were other factors accounted for (measured) that could affect outcomes? | N/A | |
7.7. | Were the measurements conducted consistently across groups? | N/A | |
8. | Was the statistical analysis appropriate for the study design and type of outcome indicators? | Yes | |
8.1. | Were statistical analyses adequately described and the results reported appropriately? | N/A | |
8.2. | Were correct statistical tests used and assumptions of test not violated? | N/A | |
8.3. | Were statistics reported with levels of significance and/or confidence intervals? | N/A | |
8.4. | Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? | N/A | |
8.5. | Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? | N/A | |
8.6. | Was clinical significance as well as statistical significance reported? | N/A | |
8.7. | If negative findings, was a power calculation reported to address type 2 error? | N/A | |
9. | Are conclusions supported by results with biases and limitations taken into consideration? | Yes | |
9.1. | Is there a discussion of findings? | N/A | |
9.2. | Are biases and study limitations identified and discussed? | N/A | |
10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
10.1. | Were sources of funding and investigators' affiliations described? | N/A | |
10.2. | Was the study free from apparent conflict of interest? | N/A | |