EAL

AWM: Estimating Resting Metabolic Rate (RMR) (2014)

Citation:

Ruiz JR, Ortega FB, Rodriguez G, Alkorta P, Labayen I. Validity of resting energy expenditure predictive equations before and after an energy-restricted diet intervention in obese women. PLoS One. 2011; 6(9): e23759.

PubMed ID: 21909404

Study Design:

Diagnostic, Validity or Reliability Study

Class:

C - Click here for explanation of classification scheme.

Quality Rating:

NEUTRAL: See Quality Criteria Checklist below.

Research Purpose:

To investigate the validity of REE predictive equations before and after a 12-week energy restricted diet intervention in Spanish obese women (BMI higher than 30kg/m²).

Inclusion Criteria:

Obese (BMI inclusion criteria 30 to 39.9)
Pre-menopausal Caucasian women from Victoria (North Spain) aged between 19 and 49 years
Non-physically active (less than 20 minutes on less than three days per week)
Weight stable (body weight changes less than 3kg over the last three months)
Provided written informed consent.

Exclusion Criteria:

History of:
- Diabetes
- Cardiovascular disease
- Pregnancy
- Total cholesterol levels higher than 300mg per dL
- Levels of triglycerides higher than 300mg per dL
- Blood pressure higher than 140/90mm Hg.
Women under medication for:
- Hypertension
- Hyperlipidemia
- Hyperuricemia
- Other illness.

Description of Study Protocol:

Recruitment

Women were volunteer participants fora 12-week energy-restricted diet intervention.

Design

Validity and reliability study.

Blinding Used

Implied with measurements.

Intervention

12-week energy-restricted diet intervention
Body weight reduction was induced by a low-energy mixed (55% carbohydrates, 30% fat, 15% protein) diet providing 600kcal less than individually estimated energy requirements based on measured REE
Individual energy requirements were estimated by indirect calorimetry using a ventilated hood system at baseline and multiplied by a factor of 1.3 for low level of physical activity
Energy content and macronutrient composition of the diet were based on American Diabetes Association nutrition recommendations
Dietary instructions were reinforced weekly by a dietitian; the consultation included both nutritional assessment and weighing
A three-day weighed food record of two weekdays and one weekend day was performed before the study and during the last week of the intervention, while one-day weighed food records were completed in weeks two, five and seven. Dietary records were analyzed by the Alimentacion y Salud food nutrient database (BitASDE General Medica Farmaceutica, Albocacer, Valencia, Spain).

Statistical Analysis

Data were analyzed using PASW (Predictive Analytics Software version 18.0)
Paired T-tests to analyze differences in changes on body weight, BMI, FM and FFM after a 12-week energy restricted diet intervention
The root mean sum of squared means were calculated and an accurate estimation when the equation predicted between 90% and 110% of the measured REE was also calculated
The agreement between REE predicted equations and measured REE was graphically examined by plotting the difference between the predicted and the measured REE
The mean difference 95% confidence intervals of the difference and the 95% limits of heteroscedasticity, that is the association between the magnitude of the measurement and the difference between the predicted and measured REE, were examined by regression analysis.

Data Collection Summary:

Timing of Measurements

Measurements made before and after the 12-week intervention.

Dependent Variables

REE was estimated by indirect calorimetry. Respiratory exchange measurements were determined by means of an open-circuit computerised indirect calorimeter (Vmax, Sensormedics) using a transparent, ventilated hood system and after daily calibration of a reference gas mixture.
Urine was collected in the post-absorptive state to determine nitrogen output
Body weight was measured after voiding using a digital integrating scale (SECA 760)
Height was measured to the nearest 5mm using a stadiometer at the start of the study
Dual Energy X-ray absorptiometry (DXA) measurements were performed within ±3 days of the pre- and post-intervention examinations
Validity of 10 REE predictive equations, based on body weight, height, sex and FM and FFM, and developed in adults. Equations derived for elderly patients, patients or athletes were excluded. Equations included:
- Harris-Benedict 1919
- Owen et al (weight)
- Owen et al (fat free mass)
- Mifflin-St. Jeor (weight)
- Mifflin-St. Jeor (fat free mass)
- FAO/OMS/UNU (weight)
- FAO/OMS/UNU (weight and height)
- Weijs and Vansant (weight and height)
- Bernstein et al (weight)
- Bernstein et al (fat free mass, fat mass).

Independent Variables

Twelve-week energy-restricted diet intervention:
- Body weight reduction was induced by a low-energy mixed (55% carbohydrates, 30% fat, 15% protein) diet providing 600kcal less than individually estimated energy requirements based on measured REE
- Individual energy requirements were estimated by indirect calorimetry using a ventilated hood system at baseline and multiplied by a factor of 1.3 for low level of physical activity
- Energy content and macronutrient composition of the diet were based on American Diabetes Association nutrition recommendations
- Dietary instructions were reinforced weekly by a dietitian; the consultation included both nutritional assessment and weighing
- A three-day weighed food record of two weekdays and one weekend day was performed before the study and during the last week of the intervention, while one-day weighed food records were completed in weeks two, five and seven. Dietary records were analyzed by the Alimentacion y Salud food nutrient database (BitASDE General Medica Farmaceutica, Albocacer, Valencia, Spain).

Description of Actual Data Sample:

Initial N: 86 women
Attrition (final N): 78 women total (dropout rate of 6%)
Age: Mean age 36.6 years
Ethnicity: Caucasian
Other relevant demographics: Mean fat mass 37.8kg
Anthropometrics: Mean BMI (kg/m²) 33.9
Location: Spain.

Summary of Results:

Key Findings

At baseline, the most accurate equation was the Mifflin et al when using weight (bias -0.2%, P=0.982), 74% of accurate predictions
This level of accuracy was not reached after the diet intervention (24% accurate prediction)
After the intervention, the lowest bias was found with the Owen et al equation when using weight (bias -1.7%, P=0.044), 81% accurate prediction, yet it provided 53% accurate predictions at baseline.

Author Conclusion:

There is a wide variation in the accuracy of REE predictive equations before and after weight loss in non-morbid obese women. The results acquire special relevance in the context of the challenging weight regain phenomenon for the overweight and obese population.

Funding Source:

University/Hospital:

University of the Basque Country

Reviewer Comments:

Questionable validity of indirect calorimeter
The authors acknowledge that they did not measure sex hormone levels to ensure that women were at the same phase of the menstrual phase.

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?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		No
	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?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	No
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?		Yes
	4.1.	Were follow-up methods described and the same for all groups?	Yes
	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	4.4.	Were reasons for withdrawals similar across groups?	Yes
	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?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	No
	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.)	Yes
	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?	Yes
	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?	Yes
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	Yes
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	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?		Yes
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	Yes
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
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?	Yes
	8.2.	Were correct statistical tests used and assumptions of test not violated?	Yes
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	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)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	Yes
	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?	Yes
	9.2.	Are biases and study limitations identified and discussed?	Yes
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes