Energy Expenditure and Physical Activity
Adriaens MP, Schoffelen PF, Westerterp KR. Intra-individual variation of basal metabolic rate and the influence of daily habitual physical activity before testing. Br J Nutr. 2003;90(2):419-423.
- 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.
- Steady state: Not defined
- BMR: Equivalent to project’s definition of RMR.
- 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.
- Refusal to consent
- Not meeting inclusion criteria.
- 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.
- Ht measured? Yes
- Wt measured? Yes
- Fat-free mass measured? Underwater weighing; 3-compartment Siri.
- 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.
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.
- N=19 volunteers (8M 11F)
- Mean age, y: 23.6±7.5 SD.
- 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.
Fat mass, kg
Fat-free mass, kg
Fat mass, kg
Fat-free mass, kg
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.
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.”
- 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.
- “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
|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|
|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|