Energy Expenditure and Physical Activity

Citation:

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.

 
Study Design:
Repeat measures
Class:
C - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:
  1. To determine the reproducibility or intra-individual variability of BMR after 3 repeated measurements, using an outpt protocol
  2. To study the effect of the within-machine variability
  3. 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:
  1. Understand and give written consent
  2. Good health with absence of metabolic diseases:
  3. No use of medication that could have affected metabolic rate
  4. Weight stability during the last 6 mos (±3 kg)
  5. Not on any special diets or participating in exercise programmes.
Exclusion Criteria:
  1. Refusal to consent
  2. 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

  1. Measured REE [(VO2, l/min), VCO2 (l/min; ml/kg/min)
  2. Physical activity with a tri-axial accelerometer for movement
  3. Total body water (H2 dilution method)
  4. 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
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