• To mathematically derive a predictive equation for REE based on a sample of 498 healthy normal-weight and obese individuals
• Assess the usefulness of the more recent body composition measures of body composition (%BF) and distribution (WHR) in predicting REE
• Assess the predictive value as well as overall practicality of the new equations compared with those currently being applied.

Definitions

• Percent ideal body weight: Determined by use of the 1959 Metropolitan Height-Weight tables
• Harris-Benedict equation: No definitions given
• Owen equation: No definitions given
• Mifflin-Jeor equation: Same as project defined
• Fat-free mass calculations: Wt (kg)-fat(kg) where fat (kg) is weight(kg)x%BF.

Recruitment by a 2x2x5 factorial design where sex and weight were stratified by five different age groups according to decade; bias toward the working class.

• Understand and give written consent
• Either the subject or spouse being employed at least half-time
• Good health with less than one sick day per month for the past year
• No major current illnesses or psychological problems
• Extreme underweight (less than 80%IBW) or morbidly obese (more than 180%IBW).

• Refusal to consent
• Subject or spouse not working at least part-time
• In poor health.

Anthropometric

Percent BF assessed using skinfold and circumference measurements taken at selected sites by trained technicians using Harpenden calipers and std techniques; sums of three SF thicknesses (i.e., thigh, triceps and suprailium for women) and (thigh, chest abdomen for men).

• Height measured: Yes, nearest 0.63cm
• Weight measured: Yes, nearest 0.55 with street clothes but without shoes
• Fat-free mass measured: Calculated from anthropometric measurements.

Clinical

• Monitored heart rate: Not reported
• Body temperature: Not reported.

Resting Energy Expenditure

• IC type: Metabolic measurement care with a canopy hood; standard computer programs converted O₂ and CO₂ gas exchanged into REE
• Rest before measure: Relaxed, supine position with a standardized relaxation tape
• Measurement length: Approximately 20 minutes per subject; measurements repeated on all subjects until a three-minute steady state was achieved
• Fasting length: Overnight
• Exercise conditioning 24 prior to test? Abstain from exercise 12 hours before the test
• Room temp: Not reported
• Number of measures repeated: Only one day for obtaining IC measurement, described in measurement length
• Coefficient of variation: None reported
• Equipment of calibration: “SF was key to our successful measurement by his training of our staff and high quality research methodology commitment.”
• Training of measurer: Trained and certified nutritionists using a standardized protocol
• Subject training of measuring process: None reported
• Other: Refrain from smoking more than one hour before testing, but for 12 hours if possible.

Outcome(s) and Other Measures

• Measured REE [(VO₂, L per minute), CO₂ (L per minute; ml per kg per minute), RER, ventilation (L per  minute)]
• Predicted REE using HB, Liu, WHO/FAO
• Independent variables of weight, height, age, BMI and fat-free mass.

Statistical Analysis

• Pearson correlation coefficients and simple and stepwise multiple regression analyses
• Data analysis limited in certain circumstances because of missing data for %BF and WHR measurements
• FFM regressions had N=482 of 498 subjects.

N=508 subjects enrolled; 10 dropouts due to inability to obtain REE measurements.

Final Sample

• Females
  • N=247
  • Mean: 44.6±14.0 years
  • Range: 20 to 76 years
  • 135 classified as normal weight (80 to less than 119% IBW)
  • 122 classified as obese (more than 120% IBW)
• Males
  • N=251
  • Mean: 44.4±14.3
  • Range: 19 to 78
  • 129 classified as normal weight (80 to less than 119% IBW)
  • 122 classified as obese (more than 120% IBW).

Unplanned Exposure Factor

• N=1 individual was less than 80% IBW
• N=2 were more than 180% IBW.

Anthropometric

Pearson Correlation Coefficients

REE and percentage FFM was shown to correlate most highly with REE (R=0.80) for the entire group of males and females.

• REE and weight: 0.72607
• REE and height: 0.68669
• REE and age: -0.26104
• REE and %IBW: 0.35497
• REE and WHR: 0.54599
• FFM and weight were correlated (R=0.79)
• FFM and height were correlated (R=0.81)
• Sex and FFM were correlated (R=0.83)
• The stepwise addition of weight, age, height and WHR increased the R2 value to 0.70; the remaining variables (sex, %IBW, and BMI) did not contribute further to the predictive value of the equation
• In an assessment of men and women as a single group, weight alone yielded a R2 value of 0.56
• In an assessment of men and women as a single group, FFM alone yielded a R2 value of 0.64
• The R2 value of approximately 0.7 seemed to be a barrier above which we could not more accurately predict REE to conclude that there is a variability of more than 30% in REE "that cannot be explained on the basis of the variables assessed in this study ... [possibly] due to individual differences in genetically determined or acquired metabolic efficiency”
• The effects of sex and obesity on REE were extensively explored by analyzing men and women, normal and overweight individuals separately. No significant differences were observed between simple regression lines for FFM in men and women within the range of values studied (males R2=0.44; females R2=0.36)
• A stepwise multiple-regression analyses of subsets of the population based on sex and %IBW did not reveal any relationships or equations surpassing the predictive value of the equation considering measured weight and height and age
• The R2 of 0.71 is obtained in using gender-specific equation of Mifflin-Jeor.

Clinical

• Measured REE for all women (N=247) had a mean of 1,349±214kcal per day and a range of 927 to 2,216kcal per day
• Measured REE for all men (N=251) had a mean of 1,776±297kcal per day and a range of 1,030 to 2,849kcal per day.

Correlation between Measured and Predicted

• Mifflin-St Jeor (this study) had the best predictors of REE with the Owen equations having the least mean difference from measured REE (-4% in females and 0.1% in males)
• HB significantly over-predicted REE in study populations (paired T-tests on individual means, P<0.01) by 5% and Cunningham equations significantly over-predicted REE in study population by 14% to 15% (by paired T-tests on individual means, P<0.01).

• The relationships between REE and several variables were studied to derive predictive equations for practical, clinical use in weight management today. The result of this process was to confirm EE is determined largely by FFM but is highly correlated with total body weight as well. Adding height, age and sex builds on the predictive value of weight in determining REE.
• Previous findings suggest HB equation over-predicts measured REE by an average of more than 15% in modern populations. In this study, there are marked differences between means for weights and ages.
• Equations are limited to their derivation from the study population; their clinical utility can be assessed by testing in other populations. Their strength and significance lie in:
  • Derivation from a larger, modern-day population (stratified by age, weight and sex)
  • Use of advanced equipment and technology for the measurement of actual REE
  • A reasonably high correlation between REE and weight, height, and age (R2=0.71)
• Direct metabolic measurements are preferable in individuals where a precise determination of REE is indicated. Other components of 24-EE (physical activity and thermic effect of food should be studied to assess more accurately the individual total daily caloric requirements)
• 30% unexplained variability in REE observed should be studied further.

Strengths

• Large sample size in comparison to other studies and stratified for age, sex and weight
• Standardized measurements.

Generalizability/Weaknesses

• Generalizability to study population with potential clinical utility with further validation testing
• Potential for small IC inaccuracy due to lack of subject training on the procedure.