- Click here for explanation of classification scheme.

To re-appraise the caloric requirements of healthy lean and obese women, some who were trained athletes, at rest and following breakfast.

 

 

• Understand and give written consent
• Eating balanced diets
• Stable weight for at least one month prior to study
• Not taking any medications
• Had no physical evidence of any physical disease
• Normal body temperatures
• Not menstruating during study periods
• Normal fasting blood-glucose concentrations
• Normal thyroid function.

Refusal to consent.

Recruitment

Specific procedures not specified.

Design

Cross-sectional study.

Statistical Analysis

• Pearson's coefficient of correlation, simple regressions and stepwise multiple regressions used to assess relationships among resting metabolic rate (RMR) and weight (WT), age, height (HT), body surface area (BSA) and measured or calculated body components
• Lean, obese and athletic women were analyzed separately and in combinations to determine the effects of body composition on RMR, thermic effect of food (TEF) and caloric storage
• T-test assuming unequal variances about the regression lines used to evaluate the derived regression lines
• Resistant-regression lines computed between RMR and WT at each point in time to analyze TEF
• Resistant-regression lines used to study the changes in carbohydrate, fat and protein oxidation before and after the breakfast mixed meal
• TEF also determined by computing the area under the four-hour RMR response curve above baseline value for each subject (the RMR measurement before the meal)
• Correlations, simple, multiple and stepwise regressions were used to study the relationships among TEF, fuel oxidation and nutrient storage vs. weight, age, BSA and measured and calculated body components.

Timing of Measurements 

• RMR: One measurement in total sample (N=44)
• TEF: Additional measurement in 32 of the 44 subjects
• Body composition studies: Additional measurements in 28 of the 32 subjects.

Dependent Variables

• Measured RMR [(VO₂, ml per minute), CO₂ (ml per minute; ml per kg per minute), RQ],  indirect calorimetry:
  • IC type: Nose clip or ventilated hood
  • Rest before measure: 30 minutes (and 240 to 360 minutes throughout)
  • Measurement length: First four to five minutes were expended to clear the machine of room air; the last five to six minutes were used for recording and calculating O₂ consumption, CO₂ production, RQ
  • Fasting length: 12 hours overnight;
  • Exercise conditioning 24 prior to test? Not reported
  • Room temp and noise: 22° to 24°C and humidity was 33%; quiet room
  • Number of measures; were they repeated? Two or three baseline values were determined at 15-minute intervals on all subjects; each value was derived from the mean of five or six one-minute values
  • Coefficient of variation? Reproducibility was studied during five different mornings for eight volunteers that underwent repeated studies to measure RMR and ranged from 0.21 to 0.061kcal per minute, and the CV was less than 4%. The CV of eight subjects between 0800 and 1,600 to 1,700 gad a CV if ±4.7%.
  • Equipment of Calibration: Yes, before and during each study by using standardized gases and a one-one syringe.
  • Training of measurer? Described in detail the validity and reliability of IC measurements
  • Subject training of measuring process? Yes
  • Intervening factor: Subjects were inconsistent about being weighed in the nude; corrections were not made for the coverings; the weight of the garments should have had an influence on results of less than 1.2% of the true value
• Predicted REE using HB, Mayo Foundation, Robertson-Reid, Cunningham
• Accuracy of prediction equations: Measured vs. predicted
• Thermic effect of food (TEF): Additional respiratory gaseous exchange rates were made every 30 minutes for four to six hours after consuming a mixed breakfast (11kcal per kg, with carbohydrate 43%, fat 42%, protein 15%) eaten during a 10-minute period
• Storage of nutrients:
  • Serum urea nitrogen, plasma total lipids, FFA, plasma
  • Urine sample: Urine alpha-amino nitrogen, urine nitrogen and elapsed time (minutes)
  • Pre- and post-prandial protein, carbohydrate and fat oxidation and storage, non-protein RQ, change in extra-cellular pool.

Independent Variables

• Age
• Weight: Measured in gown (130 to 190g) or clothes (430 to 650g)
• Height: Measured barefoot
• Body mass index (BMI): kg/m²
• Body surface area (BSA)
• Body composition: Hydrodensitometry and skinfolds
  • Fat mass: [FATMD (fat mass by densitometry), FATMSF (fat mass by skinfold thickness)]
  • Fat-free mass: [FFMD (fat mass by densitometry), FFMSF (fat mass by skinfold thickness)]
  • Lean body mass (LBM): Equation of Moore et al
  • Body cell mass (BCM).

 

• Attrition (final N): N=44 females
• Age: 35±12.2 years (range: 18 to 65).

Anthropometrics

All Women (N=44)	Mean±SD	Range
Weight, kg	74.9±24.6	43.1 to 143.3
Height, cm	164.0±6.8	150 to 180
BMI	27.8±8.6	18.2 to 49.6
BSA, m2	1.79±0.27	1.37 to 2.45
LBM, kg	45.0.0±6.8	32.7 to 58.2
BCM, kg	22.3±3.4	16.4 to 29.3
Sub-sample (N=31)
FFMD, kg	66.0±11.0	45.2 to 97.9
FATMD, kg (N=31)	20.6±15.5	3.9 to 89.9
Sub-sample (N=28)
FFMSF, kg	47.6±9.1	35.0 to 76.9
FATMSF, kg (N=28)	22.4±16.7	6.1 to 66.4

BSA=body surface area; BMI=body mass index; LMB=lean body mass, BCM=body cell mass, FFMD=fat-free mass by densitometry, FATMD=fat mass by densitometry, FFMSF=fat-free mass by skinfolds, FATMSF=fat mass by skinfolds, A:H ratio=abdominal:hip ratio.

Location

Temple  University, Philadelphia, PA.

Validity, Accuracy and Reproducibility of Indirect Calorimetry 

• The mean±SEM of the differences between mouthpiece-noseclip and the ventilated hood results was 0.003±0.54kcal per minute. The paired T-test was not statistically significant (P=0.95). The differences between the two techniques is less than 1% of the RMR mean.
• There were no significant changes in RMR (of eight subjects) while fasting and lying quietly in a comfortable position on a bed between 08:00 hours and 16:00 to 17:00 hours. The coefficient of variation during 20 different times and measuring period over approximately eight hours was ±4.7%.

RMR, Body Composition and Anthropometric Measurements

• The measured RMR varied from 870 to 2,074kcal per 24 hours and were related to body size
• Pearson Correlation Coefficients (all women)
  • RMR and age: 0.06
  • RMR and weight: 0.74
  • RMR & height: 0.41
  • RMR and BSA: 0.77
  • RMR and BMI: 0.67
  • RMR and LBM: 0.77
  • RMR and BCM: 0.77
  • RMR and FFMD: 0.71
  • RMR and FATMD: 0.66
  • RMR and FFMSF: 0.78
  • RMR and FATMSF: 0.69.
• Body weight was the most accurately and easily determined variable and was highly correlated with other measurements of active protoplasmic tissue (R>0.84); and highly correlated with RMR (R=0.74)
• Body composition variables reflecting active protoplasmic tissue such as WT, BSA, FFMSF FFMD, LBM and BCM were all highly interrelated (R>0.80)
• The highest correlation (R=0.79) was a combination of BSA and AGE but it was not statistically different from the correlation (R=0.74) for WT alone
• FFMSF and FFMD did not more accurately predict RMR when used individually and in combination. 

Measured vs. Predicted Values (kcal per 24 hours)

Predicted to mRMR	Mean ±SD	Range
Owen et al	0±152	-236 to 487
Harris-Ben	-171±158	-515 to 150
Mayo	-172±165	-172 to 15
Robertson-Reid	-91±148	-91 to 148
Cunningham	-133±154	-133 to 154

• Our measured mean ±1SD vs. predicted RMR was 0.0±152kcal per 24 hours. However, the HB, May Foundation, Robertson-Reid and Cunningham regression formulas or tables systematically overestimated RMR by 171±158, 172±165, 133±154 and 91±148kcal per 24 hours respectively.
• Stepwise regression analysis resulted in regression line slopes for the RMR and WT for non-athletic lean and obese women to be statistically indistinguishable. Both non-athletic groups of women had wide 95% confidence limits and in the resultant equation:
  • RMR (kcal per 24 hours)=795+7.18kg WT
• The regression line for athletic women (N=8) was RMR=50.4+21.1kg WT and the 95% confidence limits for the regression line was more narrow and statistically different from the non-athletic women (P<0.05)
• The regression line RMR vs. WT for the lean women alone was not significantly different from either the regression line for athletic or for the obese... testing for equality of variance among these groups clearly showed athletes to be much more predictable (i.e., less variable) than the lean women (P<0.05).

Nature and Quantity of Fuels Oxidized and TEF

• The nature and quantity of fuels oxidized by athletes and non-athletes were similar
• Dietary-induced thermogenesis was directly related to weight (R=0.66). Adding more variables did not improve the model.
• Peak oxidation rates were delayed, broadened and multiple in obese compared to lean women, and the TEF were as great, if not greater, in obese as in lean women
• Before breakfast, 22±13, 60±8 and 18±1% of the RMR were derived from the oxidation of carbohydrate, lipid and protein, respectively.
• There was a three-fold post-cibal increase on average (P<0.001) in carbohydrate oxidation rate and a slight but significant increase in protein oxidation (P<0.001). The increased postprandial oxidation rates for carbohydrate and protein were progressively delayed as body weight (and food intake) increased.
• A reciprocal relationship between carbohydrate and lipid postprandial-oxidation rates developed; simultaneously, as post-cibal carbohydrate oxidation increased, lipid oxidation decreased and vice versa.

Fasting and Four-hour Postprandial Plasma Values of Fuels

	Fasting	Four-hour Postprandial
Plasma glucose, mmol per L (mg per dL)	5.14±0.08 (92.0±2.0)	5.13+0.08 (92.0±1.0)
Urea nitrogen, mmol per L (mg per dL)	11.07±0.36(15.5±0.5)	10.60±0.28 (14.9±0.4)
Total lipid, mg per ml	4.9±0.2	5.0±0.2
Plasma α-amino nitrogen, mmol per L (mg per dL)	3.41±0.11 (4.78±0.15)	3.96±0.14 (5.54±0.19)*
Plasma FFA, μ-nik per k	643+31	304±25*

* P<0.001.

Postprandial Storage of Nutrients

• The percentage of caloric intake that was disposed of by mechanisms other than oxidation was proportional to body weight. Therefore, the heaviest individual stored the greatest number of calories in tissue deposits.
• Following a mixed meal containing enough calories to be an anabolic challenge:
  • Glucose storage was best represented by a linear function with a positive slope
  • Lipid storage was best represented by an increasing quadratic function
  • Protein storage or repletion was best represented by a decreasing square-root function.

 

As stated by the author in body of report:

• In our study, the measured RMRs for normal women were less than their predicted RMRs based on results from [available] published reports a...current regression equations overestimate the RMR of healthy women
• Due to the large variations in measured RMR, predicted RMR may over- or underestimate the measured RMR of non-athletes by 21% to 33%; the predicted RMR of a well-trained, competitive athlete estimates RMR within 8% to 10%
• The usefulness of any RMR prediction equation derived from a population with large 95% confidence limits is questionable and the metabolic requirements of humans should be measured rather than predicted
• Our data did not support the frequently made claim that RMR correlates best with LBM
• Although the absolute RMR was greater, the heavier the woman, energy expenditure per kg body weight for lean and obese non-athletic and for athletic women decreased as weight increased
• Large variances in body weight occur... a major portion of the RMR in adults women is relatively constant because of brain and liver metabolism, but the increases in RMR per kg body weight depend primarily on other body components (i.e., skeletal muscle and adipose tissue)
• RMRs of healthy women are lower than previously recognized; 2) increased metabolic efficiency should no longer be considered as an important cause of obesity in women.

Government:	US PHS, NIH
University/Hospital:	Temple University School of Medicine, Temple University

Strengths 

 

• Researchers have best described indirect calorimetry methods as any other; include validity and reliability procedures."
• Researchers also reported missing data and weighing procedure inconsistencies that helps assure weight accuracy interpretations.”

Generalizability/Weaknesses 

• Limited older women (i.e., only N=1 of more than 60 years) and unable to generalize
• Do not describe ethnic or nationalities of sample
• Convenience sample most likely highly disciplined in order to be able to relax with a patent cannula in a peripheral upper extremity vein
• The athlete subpopulation only contained eight persons and yet the 95% CI was smaller than larger sample; need to cross-validate regression equation for this population in order to establish assurance of ability to generalize to all women athletes
• An intervening variable not addressed was smoking
• Did not analyze measured versus predicted differences by weight classification. Group mean error differences excluding obese weight classifications were recalculated and found at the end of the Evidence Summary.