Adult Weight Management

Healthy Non-Obese Adults (2010-2012)

Citation:

Frankenfield DC, Rowe WA, Smith JS, Cooney RN. Validation of several established equations for resting metabolic rate in obese and non-obese people. J Am Diet Assoc. 2003; 103: 1,152-1,159.

PubMed ID: 12963943
 
Study Design:
Cross-Sectional Study
Class:
D - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To test the frequency and degree of disagreement between measured and predicted resting metabolic rate using the Harris-Benedict standard and two more recently published standards by Owen and Mifflin in order to determine: 

  • What percentage of non-obese and obese subjects are correctly predicted by each equation
  • Whether errors tend to be overestimates or underestimates
  • Whether any one of these equations should be preferred over another.
Inclusion Criteria:
  1. Adults: Age minimum 18 years
  2. Healthy
  3. Non-hospitalized
  4. Volunteers
  5. Able to give consent
  6. Non-obese and obese individuals.
Exclusion Criteria:
  1. Younger individuals
  2. Inability to ambulate
  3. Steroid use
  4. Known diabetes mellitus (because of fasting state required prior to IC) or thyroid disease
  5. No exclusions on basis of gender or race.
Description of Study Protocol:

Recruitment

Subjects were recruited by:

  • Posting flyers in various locations in hospital and medical school
  • Referrals from a weight-management clinic and a surgery clinic that evaluates morbidly obese individuals for gastric surgery
  • Referrals from family members and friends.

Design

Cross-sectional study

Blinding used 

None used; not applicable

Intervention 

Not applicable

Statistical Analysis

  • Minitab used
  • Absolute percent difference between calculated and measured values as a percent of measured resting metabolic rate (RMR) to compare each equation with measured RMR
    • Percent difference was presented in absolute terms to eliminate the mathematical tendency for negative variation to offset positive variation, thus keeping the mean near zero
  • Disagreement between measured and predicted RMR: Two values being more than 10% different from each other
    • Analysis of proportions at and<0.05 to test for significant differences in the number of disagreements between measured and predicted metabolic rate.
Data Collection Summary:

Timing of measurements

One measurement time

Dependent variables

Accuracy for predicted equations: Predicted RMR within ±10% of measured RMR.

Independent variables

  • Measured resting metabolic rate (RMR)
    • IC type: Open-circuit with gas collection via a rigid plastic canopy
    • Rest before measurement: Amount of time not described
    • Measurement length: 30 minutes with first five minutes of data discarded
    • Fasting prior to measurement: 12- to 15-hour fast overnight (away from research center)
    • Exercise restriction prior to measurement: Subjects abstained from physical exercise during the 12- to 15-hour fasting period
    • Room temperature: Ambient controlled by subject (light blankets offered)
    • Number of measurements: One 30-minute
    • Coefficient of variation: Equal to 10%.
    • Calibration of IC machine: Stated calibrated
    • Training of measurer: Not described
    • Subject given prior explanation of protocol and IC to minimize anxiety: Not discussed
    • Dietary Measurements: Not done
  • Predicted RMR:
    • Harris Benedict (1917) (5% of subjects had BMI=30kg/m2
    • Variation of Harris Benedict where all subjects with BMI=30kg/m2 had an adjusted weight substituted into the equation: Adjusted wt (kg)=( (body weight - ideal weight)x0.25) + ideal weight
      • Ideal body weight was determined from body height and calculated with the Hamwi equation
    • Owen (1986) with subjects of varying weights; 30% had BMI=30kg/m2
    • Mifflin (1990); 47% of subjects were obese with maximum BMI 42kg/m2.

[Note: Owen and Mifflin do not use weight adjustments for obesity.]

Control variables

  • Body mass index: kg/m2 calculated from measured height (without shoes; Stadiometer) and weight (in light street clothes and without shoes; Detecto Scales and Scaletronix for >160kg)
    • Obesity: 30kg/m2
    • Morbid obesity: 40kg/m2.

 

Description of Actual Data Sample:
  • Initial N: Not given
  • Attrition N (final N): N=130 (54 male, 76 female) non-hospitalized adult volunteers
  • Age: 18 years (by BMI group shown below)
  • Ethnicity: Sample was 98% Caucasian (5% from Australia or Europe, in US for at least one year to study)
  • Anthropometrics: Range of BMI18.8-96.8kg/m
    • Description of three BMI groups:
      • Non-obese
        • N=83
        • Men: Age mean: 41±2.9 SEM (Range 20-78)
        • Women: Age mean: 38±2.2 SEM (Range: 22-74)
        • Height (cm): Range 146-192
        • Weight (kg): Range 39-103
        • BMI (kg/m2): Range 15.9-29.6
        • RMR (kcal per day): Range 990-2,090
      • Obese
        • N=20
        • Men: Age mean: 39±4 SEM (Range 18-62)
        • Women: Age mean: 44±4 SEM (Range 26-69)
        • Height (cm): Range 154-189
        • Weight (kg): Range 77-133
        • BMI (kg/m2): Range 30.5-39.9
        • RMR (kcal per day): Range 1,214-2,654
      • Morbid Obese
        • N=27
        • Men: Age mean: 41±3 SEM (Range 28-57)
        • Women: Age mean: 37±2 SEM (Range 25-52)
        • Height (cm): Range 145-192
        • Weight (kg): Range 109-330
        • BMI (kg/m2): Range 40.1-96.8
        • RMR (kcal per day): Range 1,679-4,533
  • Location: Milton S. Hershey Medical Center, United States.
Summary of Results:

Major Results

Subject characteristics

  • The groups were evenly matched for height and age
  • BMI was normally distributed within the obesity groupings, but skewed toward a high BMI in the overall sample
  • BMI was greater than 30kg/m2 in 36% of subjects with 57% of those having BMI in excess of 40kg/m2
  • 56% of subjects had sedentary lifestyles; the remainder undertook physical activity for recreation rather than occupational reasons
  • Subjects whose predicted RMR was inaccurately predicted did not differ in height or age from those whose RMR was accurately predicted.

Prediction of RMR by four equations

  • For the sample as a whole, the Mifflin equation was accurate more often (78%) than either the Harris Benedict (67%, P=0.05) or Owen equations (65%, P=0.02)
  • Harris Benedict was significantly less accurate (69%) than Mifflin (82%) and Owen (73%) in non-obese subjects
  • Owen was significantly less accurate than Mifflin in all obese subjects grouped together, with the errors concentrated in the morbid obese group
    • The Mifflin equation inaccurately predicted RMR in only 25% of men and women with BMI>40kg/m2
  • When errors occurred, they tended to be overestimates for the Harris Benedict equation (using actual body weight) and underestimates for all other equations
    • Focusing on morbidly obese individuals in this study, use of Harris Benedict equation indicated a 12% overestimation using actual body weight and 22% underestimation using adjusted body weight (compared to 15% and 27%, respectively found in one validation study) 
      • Harris-Benedict overestimated RMR in 67% of men with BMI>50kg/m2
      • In women with BMI>50kg/m2, Harris-Benedict inaccurately predicted RMR in only 13%
    • The effect of using adjusted body weight in the Harris-Benedict resulted in 100% incidence of underestimation of RMR in subjects with a BMI40 kg/m2

    • Consistent underestimation was noted for the Owen equation in women with BMI40kg/m2 (92% of women).

 

Agreement between measured and predicted RMR in non-obese and obese men and women

Equation and Group Percent of subjects within±10% of RMR Percent of subjects above±10% of RMR Percent of subjects below±10% of RMR
Harris-Benedict
     
Not obese: (BMI<30), N=83 69a 27 4

All obese:

BMI30), N=47

BMI 30-40 (N=20)

BMI>40 N=27

 

64b

50

74c,d

 

30

40

22

 

6

10

4

Adjusted Harris-Benedict      

All obese (BMI 30), N=47

BMI 30-40 (N=20

BMI40 N=27

26

60

0

2

5

0

72

35

100

Owen      

Not obese (BMI <30), N=83

73 6 21

All obese (BMI30), N=83

BMI 30-40, N=20

BMI>40, N=27

51e

75

33a

6

5

7

43

20

60

Mifflin      
Not obese (BMI <30), N=83 82 10 8

All obese (BMI30), N=47

BMI 30-40, N=20

BMI>40, N=27

70

70

70

9

10

7

21

20

23

aP<0.05 vs. Mifflin of same group 

bP<0.05 vs. Harris Benedict with adjusted weight of same group 

cP<0.05 vs. Owen equation of same group 

dP<0.05 vs. Mifflin morbidly obese group

Mean percent difference between calculated and measured RMR with inaccurate predictions of RMR (i.e., calculated >10% of measured). Mean values ±SEM shown:

 Harris Benedict

  • Not obese: 13.3±0.8
  • All obese: 20.0±1.9 (P<0.05 not obese of same equation, vs. Mifflin of the same group)
  • Obese: 16.4±1.4
  • Morbid obese: 26.2±1.6 (P<0.05 not obese of the same equation, vs. Mifflin of the same group, vs. BMI 30-40 of the same equation, vs. Owen of the same group).

Harris Benedict (adjusted weight)

  • All obese: 25.0±1.3 (P<0.05 vs. Mifflin of the same group)
  • Obese: 19.5±2.1
  • Morbid obese: 26.7±1.2 (P<0.05 vs. Mifflin of the same group, vs. BMI 30-40 of the same equation, vs. Owen of the same group.

Owen

  • Not obese: 15.4±1.1
  • All obese: 16.3±1.0
  • Obese: 21.4±2.4
  • Morbid obese: 16.0±1.3.

Mifflin

  • Not obese: 13.7±1.0
  • All obese: 13.6±0.8
  • Obese: 17.4±1.6
  • Morbid obese: 13.0±1.3.

 


 

Author Conclusion:
  • Of the equations tested, the Mifflin equation provided an accurate estimate of actual RMR in the largest percentage of non-obese and obese people, with a low rate of overestimation
  • Among morbidly obese people whose RMR was not accurately predicted, the magnitude of error was smaller for the Mifflin equation than for the other equations.
  • Thus, the Mifflin equation deserves consideration as the standard for calculation of RMR in obese and non-obese individuals
  • The clinician can expect disagreement between measured and predicted RMR to be more common in obese individuals than in non-obese individuals, but those individuals who do not conform to standard cannot be identified without actually measuring RMR
  • The usual clinical maneuver of inserting an adjusted body weight into the Harris Benedict equations corrects the tendency of that equation to overestimate RMR but replaces it with a tendency to underestimate RMR
  • Although error was more likely in obese than non-obese people for all equations, there were no clinically applicable markers to identify those people whose predicted RMR should be questioned
  • Using adjusted body weight in the Harris Benedict equation caused underestimation of RMR in obesity, with the magnitude of the error increasing as BMI increased. Thus, the use of adjusted body weight is not a reasonable maneuver in the clinical setting.
  • In morbid obese individuals, the Harris Benedict equation tended to overestimate, while errors in the Owen and Mifflin equations tended to be underestimates.
Funding Source:
University/Hospital: Pennsylvania State University
Reviewer Comments:

Strengths

Wide range of BMI.

Limitations

  • Self-selection bias: Convenience sample with volunteers
  • Limited generalizability: 98% Caucasian; not representative of general population
  • Traveling to research center before measurement rather than spending night in facility (?); might affect RMR; did not discuss length of time of rest before measurement (was it long enough?)
  • Did the researchers control for physical activity (56% had sedentary lifestyles and 46% had recreational physical activity; intensity??)
  • Small sample sizes when divided into groups
  • Limitations of study not discussed.
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
  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
  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
  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
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
  1. Was the research question clearly stated? Yes
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.1. 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
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
  1.3. Were the target population and setting specified? Yes
  2. Was the selection of study subjects/patients free from bias? Yes
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? 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? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
  3. Were study groups comparable? ???
3. Were study groups comparable? ???
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) 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? ???
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? ???
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) 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? ???
  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? ???
  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.) ???
  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.) ???
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? 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. Was method of handling withdrawals described? No
  4.1. Were follow-up methods described and the same for all groups? ???
  4.1. Were follow-up methods described and the same for all groups? ???
  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%.) ???
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  4.4. Were reasons for withdrawals similar across groups? 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
  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? N/A
5. Was blinding used to prevent introduction of bias? N/A
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? N/A
  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
  5.2. 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
  5.3. 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
  5.4. 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
  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. 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
  6.1. 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? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? Yes
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  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
  6.4. 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? 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
  6.6. 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
  6.7. 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
  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. 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
  7.1. 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
  7.2. 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
  7.3. 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
  7.4. 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
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.6. Were other factors accounted for (measured) that could affect outcomes? No
  7.7. Were the measurements conducted consistently across groups? 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. 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
  8.1. 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
  8.2. 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
  8.3. 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
  8.4. 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
  8.5. 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
  8.6. 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
  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? No
9. Are conclusions supported by results with biases and limitations taken into consideration? No
  9.1. Is there a discussion of findings? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? No
  9.2. Are biases and study limitations identified and discussed? No
  10. Is bias due to study's funding or sponsorship unlikely? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes
  10.2. Was the study free from apparent conflict of interest? Yes