0021-972X/99/$03.00/0
The Journal of Clinical Endocrinology & Metabolism
Copyright © 1999 by The Endocrine Society
Vol. 84, No. 3
Printed in U.S.A.
Pubertal African-American Girls Expend Less Energy at
Rest and During Physical Activity than Caucasian Girls*
WILLIAM W. WONG, NANCY F. BUTTE, KENNETH J. ELLIS,
ALBERT C. HERGENROEDER, REBECCA B. HILL, JANICE E. STUFF,
E. O’BRIAN SMITH
AND
United States Department of Agriculture/Agricultural Research Service Children’s Nutrition Research
Center (W.W.W., N.F.B., K.J.E., J.E.S., E.O.S.) and Texas Children’s Hospital (A.C.H., R.B.H.),
Department of Pediatrics, Baylor College of Medicine, Houston, Texas 77030
ABSTRACT
Between 1963 and 1991, the most dramatic increases in the prevalence of overweight in the United States have been reported in
African-American girls. Lower basal energy expenditure and lack of
physical activity are believed to be risk factors for excessive weight
gain. We hypothesized that energy expenditure at rest and during
physical activity are lower in pubertal African-American girls than in
Caucasian girls. Basal metabolic rate and sleeping energy expenditure of 40 Caucasian and 41 African-American pubertal girls
(matched for age, physical characteristics, body fat, and energy intake) were measured by whole-room calorimetry, energy expended for
physical activity by the doubly labeled water method, sexual maturity
by physical examination, body composition by dual-energy x-ray absorptiometry, physical fitness by treadmill testing, and energy intake
by 3-day food record. After adjusting for soft lean tissue mass, the
basal energy expenditure (1333 6 132 vs. 1412 6 132 kcal/day, P 5
0.01) and energy expended for physical activity (809 6 637 vs. 1271 6
162 kcal/day, P , 0.01) were significantly lower in the African-American girls than in the Caucasian girls. The differences remained the
same after controlling for differences in sexual maturity and/or physical fitness. The lower energy expenditure of the pubertal AfricanAmerican girls suggests that they are at a higher risk of becoming
overweight than their Caucasian counterparts. (J Clin Endocrinol
Metab 84: 906 –911, 1999)
O
BESITY is a major health problem in the United States
because of its association with increased risk of hypertension, coronary heart disease, diabetes, cancer, and
many other medical ailments (1, 2). The National Health and
Nutrition Examination Survey III (3, 4) indicated that approximately 33% of American adults and 22% of American
children and adolescents are overweight. The prevalence
of overweight in African-American women is twice that in
Caucasian women, after adjustment for socioeconomic status
(5, 6). More importantly, the most dramatic increases in the
prevalence of overweight over the past 30 yr have been
observed in African-American girls, with age range-related
increases of 80 –150%, compared with an average increase of
35% in Caucasian girls (4). Overweight children are at high
risk of becoming overweight adults (7).
The etiology of overweight is multifactorial. Lower energy
expenditure is hypothesized to be one of the contributing
factors favoring positive energy balance that leads to overweight. Three recent studies reported a lower resting metabolic rate in prepubertal African-American children than in
Caucasian children (8 –10). The relationship between lower
basal energy expenditure and excessive weight gain is controversial (11–13). Lack of physical activity, however, has
been shown to be positively correlated with future weight
gain in moderately obese women (13) and in children and
adolescents (14 –16). Because physical activity decreases
through adolescence in girls (17) and fat accumulation accelerates during puberty in girls (18), lower energy expenditure during puberty may represent a greater risk for excessive weight gain in African-American girls than in
Caucasian girls. We hypothesized that rates of energy expenditure at rest and during physical activity in pubertal
African-American girls are lower than those of Caucasian
girls.
Materials and Methods
Subjects
Forty Caucasian and 41 African-American girls (Table 1) with greater
than or equal to Tanner stage 3 of breast and pubic hair development
(19) were studied. The subjects qualified for the study when both parents
and grandparents were of the same ethnicity. All subjects were healthy
and nondiabetic at the time of the study, based on medical history, vital
signs, standard clinical blood chemistries, and physical examination.
The protocol was approved by the Human Research Committee at
Baylor College of Medicine. All subjects and their parents gave written
informed consent. Body weight and height of each subject were measured to the nearest 0.1 kg and 1 mm, respectively, by one investigator.
Body mass index (BMI) was calculated as:
Received September 30, 1998. Revision received November 9, 1998.
Accepted November 16, 1998.
Address all correspondence and requests for reprints to: William W.
Wong, Ph.D., United States Department of Agriculture/Agricultural
Research Service Children’s Nutrition Research Center, 1100 Bates
Street, Houston, Texas 77030. E-mail: [email protected].
* This work was funded, in part, with federal funds from the US
Department of Agriculture, Agricultural Research Service, under Cooperative Agreement No. 58 –7MNI-6 – 001. Disclaimer: The contents
of this publication do not necessarily reflect the views or policies of the
US Department of Agriculture, nor does mention of trade names, commercial products, or organization imply endorsement by the US
Government.
BMI~kg/m2! 5
Weight
Height2
(1)
Breast and pubic hair development was determined by a physician
according to the Tanner stages of classification (19).
906
RACIAL DIFFERENCES IN ENERGY EXPENDITURE
907
TABLE 1. Age, physical characteristics, sexual maturity, and energy intake of Caucasian and African-American subjects
Caucasian
n 5 40
Age, yr
Weight, kg
Height, cm
BMI, kg/m2
Sexual maturityb
Tanner stage 3
Tanner stage 4
Tanner stage 5
Energy intake, kcal/day
Protein, %d
Fat, %d
Carbohydrate, %d
African-American
n 5 41
13.6 6 1.7
53.2 6 10.6
159.4 6 7.0
20.9 6 3.9
13.4 6 1.7
57.5 6 13.9
159.7 6 7.5
22.5 6 4.9
40.0% (27.5%)
30.0% (52.5%)
30.0% (20.0%)
1858 6 512
14.1 6 2.9
35.5 6 4.7
51.8 6 6.7
31.7% (19.5%)
7.3% (36.6%)
61.0% (43.9%)
1745 6 541
13.8 6 3.0
35.0 6 5.5
52.2 6 6.8
a
a
P
0.63
0.12
0.87
0.11
,0.01 (0.07)c
0.38
0.59
0.70
0.77
Mean 6 SD.
Percentage of subjects within each Tanner stage of breast (pubic hair) development.
c
P values by chi-square testing.
d
As percentage of total energy intake.
a
b
Cardiorespiratory fitness
The aerobic capacity of each girl (V̇O2max) was measured on a motorized treadmill until volitional exhaustion (20). Oxygen consumption
rate (V̇O2) and carbon dioxide production rate (V̇CO2) were measured
continuously by electronic metabolic analyzers, with the treadmill speed
and elevation increased at 3-min intervals. V̇O2max was achieved when
V̇O2 reached a plateau value and the respiratory exchange ratio exceeded 1.05 or when the heart rate was within 95% of the age-predicted
maximum.
Whole-room indirect calorimetry
Four room respiration calorimeters were used in the study (21). Each
subject entered the respiration chamber at 0800 h and ate breakfast at
0830 h, lunch at 1200 h, and dinner at 1730 h. All subjects received a
standardized diet consisting of approximately 30% fat, 50% carbohydrate, and 20% protein. Their energy requirements during the calorimetric visit were estimated to be 1.5 times their predicted basal metabolic
rates according to their ages, body weights, and heights, using the
Schofield’s equations (22). No food or drink other than water was allowed after 1900 h. All subjects remained awake until bedtime, at 2200 h.
Sleeping energy expenditure was measured between 2200 h and 0650 h
the next morning. At 0650 h the next morning, the subject was awakened,
urinated, and returned to bed. At 0720 h, the subject was reawakened
if she was asleep, and instructed to find a comfortable position in bed
and to refrain from movement for the next 40 min. To eliminate the
contribution of any physical activity to basal metabolic rate, only the V̇O2
and V̇CO2 data with activity counts #50 (Doppler microwave sensor
D9/50, Microwave Sensors, Ann Arbor, MI) during the 40-min measurement period were converted to basal metabolic rate, as (23): basal
metabolic rate (kcal/day) 5 (3.941 3 V̇O2) 1 (1.106 3 V̇CO2). Sleeping
energy expenditure was measured to obtain a longer and more accurate
estimate of basal energy expenditure, because basal metabolic rate can
be affected by a child’s state, i.e. anxiety, impatience, and ability to stay
motionless for 40 min. The Weir equation (23) also was used to convert
the V̇O2 and V̇CO2 measurements during sleep into sleeping energy
expenditure. A 24-h urine sample was collected from each subject while
she was in the calorimeter, to determine the urinary nitrogen excretion
rate.
Doubly labeled water method (2H218O)
The total energy expenditure of each subject under free-living conditions, which could not be measured by whole-room indirect calorimetry, was estimated using the 2H218O method. After each subject exited
the calorimeter, baseline plasma and saliva samples were collected. Each
subject then received, by mouth, 100 mg 2H2O and 125 mg 18O as H218O
(Isotec Inc., Miamisburg, OH) per kilogram body weight. The container
holding the 2H218O was rinsed three times with 50 mL of water, and the
subject ingested all the rinses. The subject collected one daily saliva
sample at home for the next 10 days. Immediately before her departure,
a 3-h postdose plasma sample was collected. To minimize fluctuation in
the basal 2H and 18O abundance in body water, all subjects resumed their
usual diets at home and refrained from travel for the next 10 days.
Plasma and saliva samples were prepared for hydrogen and oxygen
isotope ratio measurements by gas-isotope-ratio mass spectrometry (24,
25). The isotope dilution spaces for 2H (NH) and 18O (NO) were calculated
as follows:
NH or NO ~mol! 5
D 3 A 3 Ea
a 3 Ed 3 18.02
(2)
where D is the dose of 2H2O or H218O in grams; A is the amount of
laboratory water, in grams, used in the dose dilution; a is the amount
of 2H2O or H218O, in grams, added to the laboratory water in the dose
dilution; Ea is the rise in 2H or 18O abundance, per mil, in the laboratory
water after the addition of the isotopic water; Ed is the rise in 2H or 18O
abundance, per mil, in the 3-h postdose plasma sample. V̇CO2 was
calculated from the fractional turnover rates of 2H (kH) and 18O (kO) and
the isotope dilution spaces as follows (26, 27): V̇CO2 (mol/day) 5
0.4584 3 [(kO 3 NO) 2 (kH 3 NH)]. The V̇CO2 was converted to freeliving energy expenditure as follows (23): free-living energy expenditure
(kcal/day) 5 (3.941 3 V̇O2) 1 (1.106 3 V̇CO2) 2 (2.17 3 UN), where V̇O2,
in liters, is calculated from the 24-h respiratory quotient (RQ), measured
by calorimetry, using the relationship V̇O2 5 V̇CO2/RQ (28), and UN is
the 24-h urinary nitrogen excretion in grams. Energy expended for
physical activity was calculated by subtracting basal metabolic rate and
diet-induced thermogenesis from free-living energy expenditure. Dietinduced thermogenesis was assumed to be 10% of free-living energy
expenditure.
Body composition measurement
A Hologic QDR-2000 instrument (Hologic, Inc., Waltham, MA) was
used to assess the body composition of each subject. The scanning
software (version 5.56) is appropriate for the weight range of our study
subjects, and the accuracy of the fat mass and bone mineral content
measurements is independent of pubertal development (29). Fat-free
mass, in kilograms, was the difference between body weight and fat
mass. Because skeletal bone mass, a nonmetabolic component of fat-free
mass, is higher in African-American girls than in Caucasian girls (30),
soft lean tissue mass was obtained by subtracting bone mass from
fat-free mass as follows (31): soft lean tissue mass (kg) 5 (fat-free mass)
2 (1.9 3 bone mineral content).
Energy intake
At the laboratory, each subject received instructions from a dietitian
on the appropriate completion of a 3-day food record at home, including
one weekend day. Each subject practiced the procedure during her stay
in the respiration chamber. These instructions also were given to the
parent(s). Energy intake was calculated from the food records using the
908
JCE & M • 1999
Vol 84 • No 3
WONG ET AL.
Minnesota Nutrition Data System (ND 2.4, Nutrition Coordinating Center, University of Minnesota, MN, 1993).
Statistical analyses
Because soft lean tissue mass has been shown to be the major determinant of energy expenditure in children, adolescents, and adults,
whereas fat mass was only a minor contributor to energy expenditure
in obese subjects (32, 33), all energy expenditure measurements were
normalized to soft lean tissue mass (the mathematical ratio method)
before statistical analysis. A t test was used to compare ethnic groups,
with respect to age, physical characteristics, body composition, V̇O2max,
energy intake, and all measures of energy expenditure. Because Tanner
stages of pubertal development are not continuous variables, x-square
was used to compare groups on sexual maturity. Because the mathematical ratio method has been shown to yield erroneous conclusions,
regarding differences in energy expenditure (34), analysis of covariance
also was used to determine the effect of race on all measures of energy
expenditure, while controlling for soft lean tissue mass. Interactions
between covariates and race were assessed. All statistical analyses were
performed using standardized software (SPSS for Windows, version
7.5.1, SPSS, Inc., Chicago, IL).
Results
Age, physical characteristics, sexual maturity, and energy
intake of study subjects
Age, physical characteristics, sexual maturity, and energy
intake of the two groups are given in Table 1. The AfricanAmerican and Caucasian girls were well matched for age,
body weight, height, and BMI. The African-American girls,
however, were sexually more mature than the Caucasian
girls. Neither the total energy intake, estimated from the
3-day food records, nor the calorie intakes of the macronutrients (expressed as percentages of total energy intake) were
significantly different between the two groups.
V̇O2max and body composition of study subjects
As shown in Table 2, the V̇O2max of the African-American
girls was significantly lower than those of the Caucasian
girls. However, the bone mineral content, bone mass, fat-free
mass, and soft lean tissue mass of the African-American girls
were significantly higher than those of the Caucasian girls.
No difference in fat mass, expressed either in absolute kilograms or in percentage of body weight, was observed between the two groups.
Differences in rates of energy expenditure, at rest, between
the African-American and Caucasian girls
Sleeping energy expenditure and basal metabolic rate of
the African-American and Caucasian girls are summarized
in Table 3. All calorimetric measures of energy expenditure,
after normalization to soft lean tissue mass (by the mathematical ratio method) or after adjustment for soft lean tissue
mass (by analysis of covariance), were significantly lower in
the African-American girls than in the Caucasian girls. The
racial differences in the calorimetric measures of energy expenditure remained significant after inclusion of sexual maturity and/or V̇O2max in the analysis of covariance. Fat mass
was not included in the analysis because it was not different
between the two groups, one of the criteria considered as a
covariate. No significant interactions were observed between
race and any of the covariates in the analyses, indicating that
the racial differences in basal energy expenditure were not
affected by the size of soft lean tissue mass, the stages of
pubertal development, or physical fitness.
Differences in free-living energy expenditure and energy
expended for physical activity, between the AfricanAmerican and Caucasian girls
Total energy expenditure and energy expended for physical activity under free-living conditions (measured by the
doubly labeled water method) are summarized in Table 4.
The isotope dilution spaces (NH, NO) were higher in the
African-American girls than in the Caucasian girls, whereas
the fractional turnover rates of 2H and 18O were higher
among the Caucasian girls than in the African-American
girls. No significant differences were observed in the 24-h RQ
or UN rate between the two groups. Total energy expenditure
and energy expended for physical activity under free-living
conditions, after normalization to soft lean tissue mass (by
the mathematical ratio method) or after adjustment for soft
lean tissue mass (by analysis of covariance), were significantly lower in the African-American girls than in the Caucasian girls. The racial differences in total energy expenditure
and energy expended for physical activity remained significant after inclusion of sexual maturity and/or V̇O2max in the
analysis. Again, no significant interactions were observed
between race and any of the covariates in the analyses.
Discussion
Based on the weights and heights of children and adolescents reported in the National Health Examination Survey,
Cycle II (1963–1965) and the latest data recorded by the
National Health and Nutrition Examination Survey (1988 –
1991), the most dramatic increases in overweight have occurred in African-American girls (4). From 1963 to 1991, a
TABLE 2. V̇O2 max and body composition of Caucasian and African-American subjects
V̇O2 max, mL/kg z min
Body composition
Bone mineral content, kg
Bone mass, kg
Fat mass, kg
Fat mass, %
Fat-free mass, kg
Soft lean tissue mass, kg
a
Mean 6
SD.
Caucasian
n 5 40
African-American
n 5 41
P
38.0 6 7.1a
32.3 6 6.0a
,0.01
1.75 6 0.32
3.32 6 0.61
15.4 6 7.1
27.9 6 7.4
35.6 6 4.6
32.3 6 4.0
1.95 6 0.43
3.70 6 0.81
17.1 6 9.1
28.2 6 8.0
38.3 6 5.7
34.5 6 5.2
0.02
0.02
0.35
0.84
0.03
0.03
RACIAL DIFFERENCES IN ENERGY EXPENDITURE
909
TABLE 3. Energy expenditure measured by whole-room indirect calorimetry of Caucasian and African-American subjectsa
Variablesb
Total sleeping energy expenditure
kcal/kg sltm z d
kcal/d adjusted for sltmc
Basal metabolic rate
kcal/kg sltm z d
kcal/d adjusted for sltmc
a
b
c
Caucasian
n 5 40
African-American
n 5 41
P
40.2 6 4.7
1306 6 123
37.0 6 4.0
1244 6 123
,0.01
0.03
43.5 6 5.0
1412 6 132
39.7 6 4.3
1333 6 132
,0.01
0.01
Values are mean 6 SD and P value by Student t test unless indicated otherwise.
Abbreviations: sltm, soft lean tissue mass.
Mean 6 SD and P value after adjusting for soft lean tissue mass by analysis of covariance.
TABLE 4. Total energy expenditure and energy expended for physical activity under free-living conditions measured by the doubly
labeled water methoda
Variablesb
Caucasian
n 5 40
African-American
n 5 41
P
NH, mol
NO, mol
kH, d21
kO, d21
RQ
UN, g/day
Free-living energy expenditure
kcal/kg sltm z d
kcal/d adjusted for sltmc
Energy expended for physical activity
kcal/kg sltm z d
kcal/d adjusted for sltmc
1634 6 234
1597 6 236
0.0885 6 0.0308
0.1211 6 0.0358
0.894 6 0.033
9.0 6 2.1
1765 6 296
1710 6 285
0.0735 6 0.0195
0.1018 6 0.0240
0.890 6 0.025
8.2 6 2.7
,0.04
,0.06
,0.02
0.01
0.45
0.17
84.9 6 22.0
2818 6 721
72.4 6 19.1
2408 6 722
,0.02
,0.03
36.5 6 18.4
1271 6 632
25.6 6 16.5
809 6 637
,0.03
,0.02
Values are mean 6 SD and P value by Student t test unless indicated otherwise.
Abbreviations: NH, hydrogen isotope dilution space; NO, oxygen isotope dilution space; kH, fractional turnover rate of hydrogen; kO, fractional
turnover rate of oxygen; RQ, respiratory quotient; UN, urinary nitrogen excretion rate; sltm, soft lean tissue mass.
c
Mean 6 SD and P value after adjusting for soft lean tissue mass by analysis of covariance.
a
b
150% increase in overweight was observed in African-American girls between 6 and 11 yr of age, and an 80% increase was
reported for African-American girls between 12 and 17 yr of
age. During the same period, there was a significantly lower
(35%) increase in overweight among Caucasian girls 6 –17 yr
of age. Because overweight children are at high risk of becoming overweight adults (7), a request for proposal (HL98 – 010) was released by the National Heart, Lung, and Blood
Institute on April 17, 1998 to look for ways to prevent excessive weight gain during adolescence in African-American
girls through modifications in diet and physical activity.
Our data (Table 3), together with those reported recently
by Kaplan et al. (8), Morrison et al. (9), and Yanovski et al. (10),
clearly demonstrate the existence of a lower basal energy
expenditure in prepubertal and pubertal African-American
girls, compared with Caucasian girls. In this study, the sleeping energy expenditure and basal metabolic rate of the
African-American girls were 62 and 78 kcal/day, respectively, lower than those of the Caucasian girls. Although
Ravussin et al. (12) observed a direct relationship between a
lower resting metabolic rate and later weight gain in 95
southwestern American Indian adults, over a period of 2– 4
yr, the same group reported that a low resting metabolic rate
was not related to later weight gain in a larger study of 130
southwestern American Indian adults (11). In a study of 24
moderately obese women, over a period of 4 yr, Weinsier et
al. (13) reported that the small differences in basal energy
expenditure recorded were insufficient to account for later
weight gain. However, the authors (13) were able to detect
a significant relationship between lower self-reported physical activity and weight gain in these women.
Although soft lean tissue mass is the major determinant
of energy expenditure (32, 33), Tanner stages of pubertal
development were included in the analysis because the
African-American girls were sexually more mature than the
Caucasian girls, in spite of their similar chronological ages
and physical characteristics (Table 1). The advanced sexual
maturation of the African-American girls is consistent with
earlier studies showing that the mean age of onset of breast
and pubic hair development is 1–2 yr earlier in AfricanAmerican girls than in Caucasian girls (35). More importantly, the magnitude of the differences in energy expenditure between the two ethnic groups in this study remained
unchanged when sexual maturity was included in the analysis. This is in agreement with the observation by Molnar and
Schutz (32) that pubertal development has no effect on energy expenditure in children and adolescents after controlling for fat-free mass. As shown in Table 2, the V̇O2max of the
African-American girls was 15% lower than that of the Caucasian girls. This result is similar to that reported by Trowbridge et al. (36). Inclusion of V̇O2max in the analysis did not
change the outcome, confirming that soft lean tissue mass is
the major determinant of energy expenditure. The lower
V̇O2max observed in the African-American girls might be
related to a lower percentage of type I fibers in their skeletal
muscle, compared with Caucasians. African-American men
have been shown to have a lower percentage of type I fibers
than Caucasian men (37), and their V̇O2max has been shown
910
JCE & M • 1999
Vol 84 • No 3
WONG ET AL.
to be highly correlated with the percentage of type I fibers in
their skeletal muscle (38). However, a muscle biopsy, which
was not done in this study, would be required to confirm this
relationship in African-American girls. Our results (Table 4)
clearly demonstrated that energy expended for physical activity under free-living conditions was significantly lower in
the African-American girls than in the Caucasian girls.
Therefore, the lower level of physical activity in the AfricanAmerican girls might have contributed to their lower aerobic
fitness level.
As shown in Table 4, the average total energy expenditure
and energy expended by pubertal African-American girls for
physical activity under free-living conditions were, respectively, 410 and 462 kcal/day lower than the Caucasian girls’
rates, after adjustment of soft lean tissue mass, by analysis of
covariance. The magnitude of the difference was approximately 6-fold higher than that of the basal metabolic rate.
This is in contrast to the study by Trowbridge et al. (36),
showing no difference in total energy expenditure and energy expended for physical activity, under free-living conditions, between prepubertal African-American and Caucasian girls. Their inability to detect a significant difference
between the two ethnic groups might have been attributable
to an insufficient number of study subjects (18 Caucasian and
27 African-American girls).
Because a lack of physical activity has a positive correlation with excessive weight gain (13, 39), and greater increases
in adiposity have been documented in pubertal AfricanAmerican girls than in Caucasian girls (40), the substantially
lower total energy expended for physical activity, under
free-living conditions, in the pubertal African-American girls
suggests that they are at increased risk of excessive fat gain,
compared with the Caucasian girls. Therefore, any programs
to minimize or prevent overweight in African-American
women must take into account the lower energy expenditure
for physical activity in this population during childhood, as
well as in adulthood. Specifically, this study suggests that
greater caloric restriction and physical activity are indicated
for African-American girls than for Caucasian girls. Our
subjects were recruited from middle-income families. It has
been shown that children of low socioeconomic status have
lower levels of physical activity and higher body weight (41).
Therefore, it is possible that energy expenditure for physical
activity under free-living conditions is further reduced in
African-American girls in low-income families. In other
words, the risk of excessive weight gain might be highest
among African-American girls in low-income families. Longitudinal studies, particularly in African-American girls of
low socioeconomic status, are needed to evaluate the efficacy
of increasing physical activity to control excessive weight
gain and the ability to sustain positive physical activity behavior from childhood into adulthood.
Acknowledgments
The authors are indebted to the volunteers; to the staff of the Metabolic Research Unit, for meeting the needs of the subjects during the
study; to Dr. J. Hoyle in the Pediatric Department of Kelsey-Seybold
West Clinic; Dr. M. desVignes-Kendrick, Director of the City of Houston
Health and Human Services Department; Ms. X. Earlie, Director of
Sciences of the Aldine Independent School District; Ms. S. Wooten,
principal at the Teague Middle School; Dr. B. Shargey, dean of instruction, and Ms. C. C. Collins, principal at the High School for Health
Professions; and Ms. K. Wallace for subject recruitment; Dr. J. Moon, Mr.
M. Puyau, and Mr. F.A. Vohra, for the calorimetric measurements; Mr.
R. J. Shypailo and Ms. J. Pratt, for the body composition measurements;
Mrs. L. L. Clarke and Mr. S. Zhang, for the isotope ratio measurements;
and to Ms. L. Loddeke, for editorial assistance in the preparation of the
manuscript.
References
1. van Itallie TB. 1985 Health implications of overweight and obesity in the
United States. Ann Intern Med. 103:983–988.
2. Bray GA. 1985 Complications of obesity. Ann Intern Med. 103:1052–1062.
3. Kuczmarski RJ, Flegal KM, Campbell SM, Johnson CL. 1994 Increasing
prevalence of overweight among US adults. The National Health and Nutrition
Examination Survey, 1960 to 1991. JAMA. 272:205–211.
4. Troiano RP, Flegal KM, Kuczmarski RJ, Campbell SM, Johnson CL. 1995
Overweight prevalence and trends for children and adolescents. Arch Pediatr
Adolesc Med. 149:1085–1091.
5. Kumanyika S. 1987 Obesity in black women. Epidemiol Rev. 9:31–50.
6. Kumanyika SK. 1994 Obesity in minority populations: an epidemiologic assessment. Obes Res. 2:166 –182.
7. Serdula MK, Ivery D, Coates RJ, Freedman DS, Williamson DF, Byers T. 1993
Do obese children become obese adults? A review of the literature. Prev Med.
22:167–177.
8. Kaplan AS, Zemel BS, Stallings VA. 1996 Differences in resting energy expenditure in prepubertal black children and white children. J Pediatr.
129:643– 647.
9. Morrison JA, Alfaro MP, Khoury P, Thornton BB, Daniels SR. 1996 Determinants of resting energy expenditure in young black girls and young white
girls. J Pediatr. 129:637– 642.
10. Yanovski SZ, Reynolds JC, Boyle AJ, Yanovski JA. 1997 Resting metabolic
rate in African-American and Caucasian girls. Obes Res. 5:321–325.
11. Bogardus C, Lillioja S, Ravussin E, et al. 1986 Familial dependence of the
resting metabolic rate. N Engl J Med. 315:96 –100.
12. Ravussin E, Lillioja S, Knowler WC, et al. 1988 Reduced rate of energy
expenditure as a risk factor for body-weight gain. N Engl J Med. 318:467– 472.
13. Weinsier RL, Nelson KM, Hensrud DD, Darnell BE, Hunter GR, Schutz Y.
1995 Metabolic predictors of obesity. Contribution of resting energy expenditure, thermic effect of food, and fuel utilization to four-year weight gain of
post-obese and never-obese women. J Clin Invest. 95:980 –985.
14. Dietz WH, Gortmaker SL. 1985 Do we fatten our children at the television
set? Obesity and television viewing in children and adolescents. J Pediatr.
75:807– 812.
15. DeStefano R, Caprio S, Fahey J, Tamborlane WV, Goldberg B. 1997 Beneficial
effects of supervised physical activity in the management of overweight boys.
Obes Res. 5:9S.
16. Johnson ML, Burke BS, Mayer J. 1956 Relative importance of inactivity and
overeating in the energy balance of obese high school girls. Am J Clin Nutr.
4:37– 44.
17. Barsony N, Bandini LG, Must A, Dietz WH. 1997 Is adolescence a vulnerable
period for the development of a sedentary lifestyle? Obes Res. 5:3S.
18. Malina RM, Bouchard C. 1991 Adipose tissue changes during growth. In:
Growth, maturation, and physical activity. Champaign, IL: Human Kinetics
Books; 133–149.
19. Tanner JM, Whitehouse RH. 1982 Variations of growth and development at
puberty. In: Atlas of children’s growth, normal variation and growth disorders.
New York: Academic Press; 122–127.
20. Bruce RA, Kusumi F, Hosmer D. 1973 Maximal oxygen intake and nomographic assessment of functional aerobic impairment in cardiovascular disease. Am Heart J. 85:546 –562.
21. Moon JK, Vohra FA, Jimenez OSV, Puyau MR, Butte NF. 1995 Closed-loop
control of carbon dioxide concentration and pressure improves response of
room respiration calorimeters. J Nutr. 125:220 –228.
22. Schofield WN. 1995 Predicting basal metabolic rate, new standards and review
of previous work. Hum Nutr :Clin Nutr. 39C:5– 41.
23. Weir JB. 1949 New methods for calculating metabolic rate with special reference to protein metabolism. J Physiol. 109:1–9.
24. Wong WW, Lee LS, Klein PD. 1987 Deuterium and oxygen-18 measurements
on microliter samples of urine, plasma, saliva, and human milk. Am J Clin
Nutr. 45:905–913.
25. Wong WW, Clarke LL, Llaurador M, Klein PD. 1992 A new zinc product for
the reduction of water in physiological fluids to hydrogen gas for 2H/1H
isotope ratio measurements. Eur J Clin Nutr. 46:69 –71.
26. Wong WW, Cochran WJ, Klish WJ, Smith EO, Lee LS, Klein PD. 1988 In vivo
isotope-fractionation factors and the measurement of deuterium- and oxygen18-dilution spaces from plasma, urine, saliva, respiratory water vapor, and
carbon dioxide. Am J Clin Nutr. 47:1– 6.
27. Wong WW. 1994 Energy expenditure of female adolescents. J Am Coll Nutr.
13:332–337.
RACIAL DIFFERENCES IN ENERGY EXPENDITURE
28. Jensen CL, Butte NF, Wong WW, Moon JK. 1992 Determining energy expenditure in preterm infants: comparison of 2H218O method and indirect
calorimetry. Am J Physiol. 263:R685–R692.
29. Shypailo RJ, Posada JKJ, Ellis KJ. 1998 Whole-body phantoms with anthropomorphic-shaped skeletons for evaluation of dual-energy x-ray absorptiometry measurements. Appl Radiat Isot. 49:503–505.
30. Ellis KJ, Abrams SA, Wong WW. 1997 Body composition of a young, multiethnic female population. Am J Clin Nutr. 65:724 –731.
31. Snyder WS, Cook MJ, Nasset ES, Karhausen LR, Howells GP, Tipton IH.
1981 Weights of organs and tissues of reference man. In: Report of the Task
Group on Reference Man. 1st ed. New York: Pergamon Press; 325–328.
32. Molnar D, Schutz Y. 1997 The effect of obesity, age, puberty and gender
on resting metabolic rate in children and adolescents. Eur J Pediatr.
156:376 –381.
33. Cunningham JJ. 1991 Body composition as a determinant of energy expenditure: a synthetic review and a proposed general prediction equation. Am J
Clin Nutr. 54:963–969.
34. Poehlman ET, Toth MJ. 1995 Mathematical ratios lead to spurious conclusions
regarding age- and sex-related differences in resting metabolic rate. Am J Clin
Nutr. 61:482– 485.
35. Herman-Giddens ME, Slora EJ, Wasserman RC, et al. 1997 Secondary
36.
37.
38.
39.
40.
41.
911
sexual characteristics and menses in young girls seen in office practice: a
study from the Pediatric Research in Office Settings Network. Pediatrics.
99:505–512.
Trowbridge CA, Gower BA, Nagy TR, Hunter GR, Treuth MS, Goran MI.
1997 Maximal aerobic capacity in African-American and Caucasian prepubertal children. Am J Physiol. 273:E809 –E814.
Ama PFM, Simoneau JA, Boulay MR, Serresse O, Theriault G, Bouchard C.
1986 Skeletal muscle characteristics in sedentary Black and Caucasian males.
J Appl Physiol. 61:1758 –1761.
Ivy JL, Costill DL, Maxwell BD. 1980 Skeletal muscle determinants of maximum aerobic power in man. Eur J Appl Physiol. 44:1– 8.
Dietz WH, Gortmaker SL. 1984 Factors within the physical environment
associated with childhood obesity. Am J Clin Nutr. 39:619 – 624.
Kimm SYS, Barton BA, Obarzanek E, Crawford P. 1997 Changes in adiposity
in a biracial cohort during puberty: NHLBI growth and health study. Can
J Cardiol. 13:218B.
Filozof C, Zuckerfeld R, Berguella AM, Saenz S, Veiga G, Gonzalez C. 1997
Higher relative weight in kids of lower socioeconomic groups is associated
with lower levels of physical activity and higher perceived stress. Obes Res.
5:11S.
European Federation of Endocrine Societies
3rd Postgraduate Course in Molecular and Cellular Endocrinology July 7–11, 1999
Münster, Germany
Topics: Introductory lectures on hormone action, selected endocrine topics, endocrinology and reproduction
and development, workshops on molecular and cellular techniques in endocrinology, technology lectures.
Deadline for registration: May 1, 1999. Number of registrations will be limited to 120 on a first-comefirst-serve-basis. Registration fee: 150 EURO/294 DM.
The final programme and the registration form are available at the Course Secretariat: Institute of Reproductive Medicine, Domagkstr. 11 D-48129 Münster, Germany. Tel: 149/251-835 6097; Fax: 149/251-835
6093; E-mail: [email protected]