ADOLESCENT MEDICINE
Estimates of metabolic rate in obese and nonobese adolescents W i l l i a m H. Dietz, MD, PhD, L i n d a G. Bandini, RD, PhD, a n d D a l e A. Schoeller, PBD From the Department of Pediatric Gastroenterology and Nutrition, New England Medical Center, Boston, Massachusetts, and the Clinical Nutrition Research Unit, University of Chicago, Chicago, Illinois
To evaluate the validity of equations for the calculation of basal metabolic rate, we c o m p a r e d measured metabolic rates in a population thal included obese and nonobese adolescents with metabolic rates calculated from five equations commonly used to estimate metabolic rate. Of the available options, neither the Mayo Clinic nomogram nor the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) equations produced estimates that differed significantly from measured values. In a second cohort of severely obese adolescent girls, the FAO/WHO/UNU equation that included both height and weight provided the most accurate estimate of metabolic rate. Because of their simplicity, we recommend use of the FAO/WHO/UNU equations to estimate metabolic rate in adolescent populations (boys: BMR = 17.5 weight [kg] + 651; girls: BMR = 12.2 weight [kg] + 746). However, when obese cohorts are studied, the FAO/WHO/UNU equation that inc!udes both weight and height predicts metabolic rate most accurately (boys: BMR = 16.6 weight [kg] § 77 height [m] + 572; girls: BMR = 7.4 weight [kg] + 482 height [m] + 217). (J PEDIATR 1991;118:146-9)
Lack of validated standards for the estimation of energy requirements in both obese and nonobese children and adolescents poses a significant problem for those who care for hospitalized pediatric patients. Underestimates of energy requirements when intravenous nutrition is provided may require the malnourished or stressed patient to use limited reserves; whereas overestimates of energy needs may promote the needless use of expensive intravenous solutions. Likewise, estimates of total daily energy expenditure based on basal metabolic rate provide the basis for estimates of energy requirements for populations and, therefore, the adequacy Of energy intakes for these groups. Overestimates or
underestimates of population needs may have significant implications for program planningl We have recently studied BMRs in a group of obese and nonobese adolescents.1 These data have allowed us to compare our measured metabolic rates with those estimated from standard equations and thereby to evaluate the validity of previous estimates.
Supported by National Institutes of Health grants No. DK 26678 and No. RR 00088. Submitted for publication March 21, 1990; accepted Aug. 23, 1990. Reprint requests: William H. Dietz, MD, PhD, New England Medical Center, Box 213, Divisionof Pediatric Gastroenterology/ Nutrition, 750 Washington St., Boston, MA 02111. 9/20/24941
METHODS
146
BMR FAO/WHO/UNU
FFM
Basal metabolic rate Food and Agriculture Organization, World Health Organization, United Nations university Fat-free mass
This study was approved by the human investigations review committees of the New England Medical Center and the Massachusetts Institute of Technology. The first Cohort consisted of 54 obese and nonobese adolescents recruited for a study designed to compare BMR and total energy expenditure. Although 63 obese and nonobese adolescents were
Volume 118 Number 1
E s t i m a t e s o f B M R in adolescents
14 7
Table I, Equations for the estimation of basal or resting energy expenditure (kcal/day) in adolescents Harris-Benedict
Mayo nomogram Cunningham FAO/WHO/UNU
(Males) BEE = 66.473 + 5.003 (height [cm]) + 13.752 (weight [kg]) -6.755 (age) (Females) BEE = 655.096+ 1.850 (height [cm])+ 9.563 (weight [kg]) -4.676 (age) REE = 24 (BMR* [kcal/m2]) (surface area [m2]) BEE = 500 + 22 (lean body mass [kg]) No. 1 (Boys 10-18 yr) BEE = 17.5 weight [kg] + 651 (Girls 10-18 yr) BEE = 12.2 weight [kg] + 746 No. 2 (Boys 10-18 yr) BMR = 16.6 weight [kg] + 77 height [m] + 572 (Girls 10-18 yr) BMR = 7.4 weight [kg] + 482 height [m] + 217
BEE, Basal energyexpenditure;REE. restingenergyexpenditure.
*Age and sex specific.
originally studied, 1 duplicate measurements of BMR with the use of a ventilated hood were available from only 14 nonobese and 15 obese boys and 12 nonobese and 13 obese girls. Clinical and anthropometric data have been published elsewhere. 1 The degree of obesity ranged from mild to severe. Therefore the sample reflects the range of body composition that may be found in a normal population. A regression equation for BMR on fat-free mass was derived from the 25 obese and nonobese girls from this study and has also been published elsewhere (BMR = 25.438 + 34.913 FFM; r = 0.92) 1. The FFM and BMR were measured in a second cohort of 13 severely obese adolescent girls. Metabolic rates estimated from the standard equations found acceptable in the first population and the regression equation derived from the 25 obese and nonobese girls studied previously were compared with metabolic rates measured in the severely obese cohort. All subjects entered the Massachusetts Institute of Technology Clinical Research Center the night before the study. After the consent form was signed, a standard medical history was obtained and a physical examination was performed. Aside from their obesity, all subjects were in good health. One girl was taking oral contraceptives. Two obese subjects and one nonobese subject had abnormal glucose tolerance test findings. Total body water was measured overnight with the use of H20 is, as we have described elsewhere. 2 The BMR was studied by means of an opencircuit indirect calorimeter. After an overnight fast, subjects were awakened to void. Thereafter they lay quietly in bed for approximately 30 minutes. Subsequently the metabolic rate was measured for 30 minutes. Metabolic rate measured in the first cohort (n = 54) was compared with the metabolic rate estimated from five equations commonly used to estimate metabolic rate in adolescents. These included the Harris-Benedict equation,3 the Mayo Clinic nomogram,4 an equation developed by Cunningham,5 and two sets of equations developed by the Food and Agriculture Organization, World Health Orga-
nization, and United Nations University.6 These equations are summarized in Table I. The terms used in Table I are those used by the authors of the equations and refer to the conditions under which metabolic rate was measured. Under optimal circumstances, the measurements of basal energy expenditure and metabolic rate a t rest are equivalent to basal metabolic rate, measured under standardized conditions. The term "resting energy expenditure" is equivalent to resting metabolic rate. Because we measured basal metabolic rate, we will refer to our measurements throughout as BMR. The Harris-Benedict equation3 was derived from indirect calorimetric studies of 239 normal subjects, most of whom were adults, and is probably the most widely used equation for estimation of energy requirements. The equation relies on the use of height, weight, and age multiplied by genderspecific constants. The Mayo Clinic nomogram4 was derived from the study of a large sample of normal persons, including children and adolescents, by indirect calorimetry. The equation itself involves the multiplication of surface area, calculated from stature and weight, by a constant that differs for age and gender. These data were subsequently used to establish a gender- and age-specific nomogram. Cunningham's equation 5 relied on reanalysis of the original Harris-Benedict data. Because FFM, or lean body mass, is the active metabolic tissue of the body, Cunningham estimated lean body mass on the basis of gender, age, height, and weight, and entered these values in a regression equation. His results suggested that BMR could best be estimated from a simple linear equation that included lean body mass and was comparable for both male and female subjects. The F A O / W H O / U N U equations were based on equations derived from studies of metabolic rate in more than 7000 persons] Mean scores and standard deviations from an additional group of 4000 subjects provided observations to validate the equations derived from individual data. The majority of the studies that provided the data were performed before 1940 with the use of either Douglas
14 8
Dietz, Bandini, and Schoeller
The Journal of Pediatrics January 1991
Table II. Comparison of measured basal metabolic rate results with BMR estimated from standard predictive equations in a population of male and female adolescents
Method Measured BMR Harris-Benedict Mayo Clinic nomogram Cunningham FAO/WHO/UNU No. 1 FAO/WHO/UNU No. 2
Measured or predicted (kcal/day)
Measured/ predicted (%)
1859 _+ 405 1780 • 370 1941 __+346 1594 • 249 1883 • 469
100 104.6 + 8.9* 96.0 +_ 7.7 116.0 +_ 12.9" 99.7 • 9.2
1818 _+ 439
103.0 _+ 10.1
Table IV. Comparisons of measured basal metabolic rate to BMR estimated from fat free mass, the Mayo Clinic nomogram, and the F A O / W H O / U N U equations in 13 severely obese female adolescents
Method
Measured or predicted (kcal/day)
Measured/ predicted (%)
Measured FFM regression (n = 25) Mayo Clinic nomogram FAO/WHO/UNU No. 1 FAO/WHO/UNU No. 2
1794 + 225 1890 +_ 294 1974 _+ 177 1985 _+ 239 1756 _+ 158
95.6 _+ 7.2 90.9 • 7.8* 90.5 _+ 6.2* 102.0 _+ 7.0
Values are expressed as means + SD. *p
Estimates of metabolic rate in obese and nonobese adolescents W i l l i a m H. Dietz, MD, PhD, L i n d a G. Bandini, RD, PhD, a n d D a l e A. Schoeller, PBD From the Department of Pediatric Gastroenterology and Nutrition, New England Medical Center, Boston, Massachusetts, and the Clinical Nutrition Research Unit, University of Chicago, Chicago, Illinois
To evaluate the validity of equations for the calculation of basal metabolic rate, we c o m p a r e d measured metabolic rates in a population thal included obese and nonobese adolescents with metabolic rates calculated from five equations commonly used to estimate metabolic rate. Of the available options, neither the Mayo Clinic nomogram nor the Food and Agriculture Organization/World Health Organization/United Nations University (FAO/WHO/UNU) equations produced estimates that differed significantly from measured values. In a second cohort of severely obese adolescent girls, the FAO/WHO/UNU equation that included both height and weight provided the most accurate estimate of metabolic rate. Because of their simplicity, we recommend use of the FAO/WHO/UNU equations to estimate metabolic rate in adolescent populations (boys: BMR = 17.5 weight [kg] + 651; girls: BMR = 12.2 weight [kg] + 746). However, when obese cohorts are studied, the FAO/WHO/UNU equation that inc!udes both weight and height predicts metabolic rate most accurately (boys: BMR = 16.6 weight [kg] § 77 height [m] + 572; girls: BMR = 7.4 weight [kg] + 482 height [m] + 217). (J PEDIATR 1991;118:146-9)
Lack of validated standards for the estimation of energy requirements in both obese and nonobese children and adolescents poses a significant problem for those who care for hospitalized pediatric patients. Underestimates of energy requirements when intravenous nutrition is provided may require the malnourished or stressed patient to use limited reserves; whereas overestimates of energy needs may promote the needless use of expensive intravenous solutions. Likewise, estimates of total daily energy expenditure based on basal metabolic rate provide the basis for estimates of energy requirements for populations and, therefore, the adequacy Of energy intakes for these groups. Overestimates or
underestimates of population needs may have significant implications for program planningl We have recently studied BMRs in a group of obese and nonobese adolescents.1 These data have allowed us to compare our measured metabolic rates with those estimated from standard equations and thereby to evaluate the validity of previous estimates.
Supported by National Institutes of Health grants No. DK 26678 and No. RR 00088. Submitted for publication March 21, 1990; accepted Aug. 23, 1990. Reprint requests: William H. Dietz, MD, PhD, New England Medical Center, Box 213, Divisionof Pediatric Gastroenterology/ Nutrition, 750 Washington St., Boston, MA 02111. 9/20/24941
METHODS
146
BMR FAO/WHO/UNU
FFM
Basal metabolic rate Food and Agriculture Organization, World Health Organization, United Nations university Fat-free mass
This study was approved by the human investigations review committees of the New England Medical Center and the Massachusetts Institute of Technology. The first Cohort consisted of 54 obese and nonobese adolescents recruited for a study designed to compare BMR and total energy expenditure. Although 63 obese and nonobese adolescents were
Volume 118 Number 1
E s t i m a t e s o f B M R in adolescents
14 7
Table I, Equations for the estimation of basal or resting energy expenditure (kcal/day) in adolescents Harris-Benedict
Mayo nomogram Cunningham FAO/WHO/UNU
(Males) BEE = 66.473 + 5.003 (height [cm]) + 13.752 (weight [kg]) -6.755 (age) (Females) BEE = 655.096+ 1.850 (height [cm])+ 9.563 (weight [kg]) -4.676 (age) REE = 24 (BMR* [kcal/m2]) (surface area [m2]) BEE = 500 + 22 (lean body mass [kg]) No. 1 (Boys 10-18 yr) BEE = 17.5 weight [kg] + 651 (Girls 10-18 yr) BEE = 12.2 weight [kg] + 746 No. 2 (Boys 10-18 yr) BMR = 16.6 weight [kg] + 77 height [m] + 572 (Girls 10-18 yr) BMR = 7.4 weight [kg] + 482 height [m] + 217
BEE, Basal energyexpenditure;REE. restingenergyexpenditure.
*Age and sex specific.
originally studied, 1 duplicate measurements of BMR with the use of a ventilated hood were available from only 14 nonobese and 15 obese boys and 12 nonobese and 13 obese girls. Clinical and anthropometric data have been published elsewhere. 1 The degree of obesity ranged from mild to severe. Therefore the sample reflects the range of body composition that may be found in a normal population. A regression equation for BMR on fat-free mass was derived from the 25 obese and nonobese girls from this study and has also been published elsewhere (BMR = 25.438 + 34.913 FFM; r = 0.92) 1. The FFM and BMR were measured in a second cohort of 13 severely obese adolescent girls. Metabolic rates estimated from the standard equations found acceptable in the first population and the regression equation derived from the 25 obese and nonobese girls studied previously were compared with metabolic rates measured in the severely obese cohort. All subjects entered the Massachusetts Institute of Technology Clinical Research Center the night before the study. After the consent form was signed, a standard medical history was obtained and a physical examination was performed. Aside from their obesity, all subjects were in good health. One girl was taking oral contraceptives. Two obese subjects and one nonobese subject had abnormal glucose tolerance test findings. Total body water was measured overnight with the use of H20 is, as we have described elsewhere. 2 The BMR was studied by means of an opencircuit indirect calorimeter. After an overnight fast, subjects were awakened to void. Thereafter they lay quietly in bed for approximately 30 minutes. Subsequently the metabolic rate was measured for 30 minutes. Metabolic rate measured in the first cohort (n = 54) was compared with the metabolic rate estimated from five equations commonly used to estimate metabolic rate in adolescents. These included the Harris-Benedict equation,3 the Mayo Clinic nomogram,4 an equation developed by Cunningham,5 and two sets of equations developed by the Food and Agriculture Organization, World Health Orga-
nization, and United Nations University.6 These equations are summarized in Table I. The terms used in Table I are those used by the authors of the equations and refer to the conditions under which metabolic rate was measured. Under optimal circumstances, the measurements of basal energy expenditure and metabolic rate a t rest are equivalent to basal metabolic rate, measured under standardized conditions. The term "resting energy expenditure" is equivalent to resting metabolic rate. Because we measured basal metabolic rate, we will refer to our measurements throughout as BMR. The Harris-Benedict equation3 was derived from indirect calorimetric studies of 239 normal subjects, most of whom were adults, and is probably the most widely used equation for estimation of energy requirements. The equation relies on the use of height, weight, and age multiplied by genderspecific constants. The Mayo Clinic nomogram4 was derived from the study of a large sample of normal persons, including children and adolescents, by indirect calorimetry. The equation itself involves the multiplication of surface area, calculated from stature and weight, by a constant that differs for age and gender. These data were subsequently used to establish a gender- and age-specific nomogram. Cunningham's equation 5 relied on reanalysis of the original Harris-Benedict data. Because FFM, or lean body mass, is the active metabolic tissue of the body, Cunningham estimated lean body mass on the basis of gender, age, height, and weight, and entered these values in a regression equation. His results suggested that BMR could best be estimated from a simple linear equation that included lean body mass and was comparable for both male and female subjects. The F A O / W H O / U N U equations were based on equations derived from studies of metabolic rate in more than 7000 persons] Mean scores and standard deviations from an additional group of 4000 subjects provided observations to validate the equations derived from individual data. The majority of the studies that provided the data were performed before 1940 with the use of either Douglas
14 8
Dietz, Bandini, and Schoeller
The Journal of Pediatrics January 1991
Table II. Comparison of measured basal metabolic rate results with BMR estimated from standard predictive equations in a population of male and female adolescents
Method Measured BMR Harris-Benedict Mayo Clinic nomogram Cunningham FAO/WHO/UNU No. 1 FAO/WHO/UNU No. 2
Measured or predicted (kcal/day)
Measured/ predicted (%)
1859 _+ 405 1780 • 370 1941 __+346 1594 • 249 1883 • 469
100 104.6 + 8.9* 96.0 +_ 7.7 116.0 +_ 12.9" 99.7 • 9.2
1818 _+ 439
103.0 _+ 10.1
Table IV. Comparisons of measured basal metabolic rate to BMR estimated from fat free mass, the Mayo Clinic nomogram, and the F A O / W H O / U N U equations in 13 severely obese female adolescents
Method
Measured or predicted (kcal/day)
Measured/ predicted (%)
Measured FFM regression (n = 25) Mayo Clinic nomogram FAO/WHO/UNU No. 1 FAO/WHO/UNU No. 2
1794 + 225 1890 +_ 294 1974 _+ 177 1985 _+ 239 1756 _+ 158
95.6 _+ 7.2 90.9 • 7.8* 90.5 _+ 6.2* 102.0 _+ 7.0
Values are expressed as means + SD. *p
