OBESITY is a major health problem in the United States

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1 X199/$03.00/0 The Journal of Clinical Endocrinology & Metabolism Coyright 1999 by The Endocrine Society Vol. 84, No.3 Printed in U.S.A. Pubertal African-American Girls Exend Less Energy at Rest and During Physical Activity than Girls* WILLIAM W. WONG, NANCY F. BUTTE, KENNETH J. ELLIS, ALBERT C. HERGENROEDER, REBECCA B. HILL, JANICE E. STUFF, AND E. O'BRIAN SMITH United States Deartment ofagriculture /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 Hosital (A.C.H., R.B.H.), Deartment ofpediatrics, Baylor College of Medicine, Houston, Texas ABSTRACT by hysical examination, body comosition by dual-energy x-ray ab Between 1963 and 1991, the most dramatic increases in the rev sortiometry, hysical fitness by treadmill testing, and energy intake alence of overweight in the United States have been reorted in by 3-day food record. After adjusting for soft lean tissue mass, the African-American girls. Lower basal energy exenditure and lack of basal energy exenditure (1333 ::':: 132 us ::':: 132 kcavday, P = hysical activity are believed to be risk factors for excessive weight 0.01) and energy exended for hysical activity (809 ::':: 637 us ::':: gain. We hyothesized that energy exenditure at rest and during 162 kcavday, P < 0.01) were significantly lower in the African-Amerhysical activity are lower in ubertal African-American girls than in ican girls than in the girls. The differences remained the girls. Basal metabolic rate and sleeing energy exendi same after controlling for differences in sexual maturity and/or hysture of 40 and 41 African-American ubertal girls ical fitness. The lower energy exenditure of the ubertal African (matched for age, hysical characteristics, body fat, and energy in American girls suggests that they are at a higher risk of becoming take) were measured by whole-room calorimetry, energy exended for overweight than their counterarts. (J Clin Endocrinol hysical activity by the doubly labeled water method, sexual maturity Metab 84: , 1999) OBESITY is a major health roblem in the United States because of its association with increased risk of hyertension, coronary heart disease, diabetes, cancer, and many other medical ailments (1, 2). The National Health and Nutrition Examination Survey III (3, 4) indicated that aroximately 33% of American adults and 22% of American children and adolescents are overweight. The revalence of overweight in African-American women is twice that in women, after adjustment for socioeconomic status (5, 6). More imortantly, the most dramatic increases in the revalence of overweight over the ast 30 yr have been observed in African-American girls, with age range-related increases of %, comared with an average increase of 35% in girls (4). Overweight children are at high risk of becoming overweight adults (7). The etiology of overweight is multifactorial. Lower energy exenditure is hyothesized to be one of the contributing factors favoring ositive energy balance that leads to overweight. Three recent studies reorted a lower resting metabolic rate in reubertal African-American children than in Received Setember 30, Revision received November 9,1998. Acceted November 16, Address all corresondence and requests for rerints to: William W. Wong, PhD., United States Deartment of Agriculture/Agricultural Research Service Children's Nutrition Research Center, 1100 Bates Street, Houston, Texas wwong@bcm.tmc.edu. This work was funded, in art, with federal funds from the US Deartment of Agriculture, Agricultural Research Service, under Cooerative Agreement No. 58-7MNI Disclaimer: The contents of this ublication do not necessarily reflect the views or olicies of the US Deartment of Agriculture, nor does mention of trade names, commercial roducts, or organization imly endorsement by the US Government. children (8-10). The relationshi between lower basal energy exenditure and excessive weight gain is controversial (11-13). Lack of hysical activity, however, has been shown to be ositively correlated with future weight gain in moderately obese women (13) and in children and adolescents (14-16). Because hysical activity decreases through adolescence in girls (17) and fat accumulation accelerates during uberty in girls (18), lower energy exenditure during uberty may reresent a greater risk for excessive weight gain in African-American girls than in girls. We hyothesized that rates of energy exenditure at rest and during hysical activity in ubertal African-American girls are lower than those of girls. Subjects Materials and Methods Forty and 41 African-American girls (Table 1) with greater than or equal to Tanner stage 3 of breast and ubic hair develoment (19) were studied. The subjects qualified for the study when both arents and grandarents 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 hysical examination. The rotocol was aroved by the Human Research Committee at Baylor College of Medicine. All subjects and their arents gave written informed consent. Body weight and height of each subject were measured to the nearest 0.1 kg and 1 mm, resectively, by one investigator. Body mass index (BMI) was calculated as: 2 Weight BMl(kg/m ) = Height2 (1) Breast and ubic hair develoment was determined by a hysician according to the Tanner stages of classification (19). 906

2 RACIAL DIFFERENCES IN ENERGY EXPENDITURE 907 TABLE 1. Age, hysical characteristics, sexual maturity, and energy intake of and African-American subjects African-American Age, yr 13.6 ::':: ::':: Weight, kg 53.2::':: ::':: Height, cm ::':: ::':: BMI, kg/m ::':: ::':: Sexual maturity" <0.01 (0.07)C Tanner stage % (27.5%) 31.7% (19.5%) Tanner stage % (52.5%) 7.3% (36.6%) Tanner stage % (20.0%) 61.0% (43.9%) Energy intake, kcal/day 1858 ::':: ::':: Protein, %d 14.1::':: ::':: Fat, %d 35.5::':: ::':: Carbohydrate, %d 51.8 ::':: ::':: Mean::':: SD. b Percentage of subjects within each Tanner stage of breast (ubic hair) develoment. CP values by chi-square testing. d As ercentage of total energy intake. Cardioresiratory fitness The aerobic caacity of each girl (V0 2max ) was measured on a motorized treadmill until volitional exhaustion (20). Oxygen consumtion rate (V02) and carbon dioxide roduction rate (Ve0 2 ) were measured continuously by electronic metabolic analyzers, with the treadmill seed and elevation increased at 3-min intervals. V0 2max was achieved when 11'0 2 reached a lateau value and the resiratory exchange ratio exceeded 1.05 or when the heart rate was within 95% of the age-redicted maximum. Whole-room indirect calorimetry Four room resiration calorimeters were used in the study (21). Each subject entered the resiration 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 aroximately 30% fat, 50% carbohydrate, and 20% rotein. Their energy requirements during the calorimetric visit were estimated to be 1.5 times their redicted 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. AU subjects remained awake until bedtime, at 2200 h. Sleeing energy exenditure 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 aslee, and instructed to find a comfortable osition in bed and to refrain from movement for the next 40 min. To eliminate the contribution of any hysical activity to basal metabolic rate, only the 11'0 2 and ve02 data with activity counts ~ 50 (Doler microwave sensor 09/50, Microwave Sensors, Ann Arbor, MI) during the 40-min measurement eriod were converted to basal metabolic rate, as (23): basal metabolic rate (kcal/day) = (3.941 x 11'02) + (1.106 x Ve02). Sleeing energy exenditure was measured to obtain a longer and more accurate estimate of basal energy exenditure, because basal metabolic rate can be affected by a child's state, i.e. anxiety, imatience, and ability to stay motionless for 40 min. The Weir equation (23) also was used to convert the 11'0 2 and ve02 measurements during slee into sleeing energy exenditure. A 24-h urine samle was collected from each subject while she was in the calorimeter, to determine the urinary nitrogen excretion rate. Doubly labeled water method (2H/ B O) The total energy exenditure of each subject under free-living conditions, which could not be measured by whole-room indirect calorimetry, was estimated using the 2H method. After each subject exited the calorimeter, baseline lasma and saliva samles were collected. Each subject then received, by mouth, 100 mg 2H 2 0 and 125 mg 18 0 as H (Isotec Inc., Miamisburg, OH) er kilogram body weight. The container holding the 2H was rinsed three times with 50 ml of water, and the subject ingested all the rinses. The subject collected one daily saliva samle at home for the next 10 days. Immediately before her dearture, a 3-h ostdose lasma samle was collected. To minimize fluctuation in the basal 2 H and 18 0 abundance in body water, all subjects resumed their usual diets at home and refrained from travel for the next 10 days. Plasma and saliva samles were reared for hydrogen and oxygen isotoe ratio measurements by gas-isotoe-ratio mass sectrometry (24, 25). The isotoe dilution saces for 2H (NH) and 18 0 (No) were calculated as follows: o x A x Ea NHor No (mol) = Ci X Ed x (2) where 0 is the dose of 2H 2 0 or H in grams; A is the amount of laboratory water, in grams, used in the dose dilution; Ci is the amount of 2H20 or H2 18 0, in grams, added to the laboratory water in the dose dilution; E" is the rise in 2H or 18 0 abundance, er mil, in the laboratory water after the addition of the isotoic water; Ed is the rise in 2H or 18 0 abundance, er mil, in the 3-h ostdose lasma samle. ve0 2 was calculated from the fractional turnover rates of 2H (kh) and 18 0 (ko) and the isotoe dilution saces as follows (26, 27): ve0 2 (mol/day) = x [(ko x No) - (kh x NH)] The ve0 2 was converted to freeliving energyexenditure as follows (23): free-living energy exenditure (kcal/day) = (3.941 x 11'02) + (1.106 x Ve02) - (2.17 x UN), where VOz, in liters, is calculated from the 24-h resiratory quotient (RQ), measured by calorimetry, using the relationshi 11'02 = Ve0 2/RQ (28), and UN is the 24-h urinary nitrogen excretion in grams. Energy exended for hysical activity was calculated by subtracting basal metabolic rate and diet-induced thermogenesis from free-living energy exenditure. Oietinduced thermogenesis was assumed to be 10% of free-living energy exenditure. Body comosition measurement A Hologic QOR-2000 instrument (Hologic, Inc., Waltham, MA) was used to assess the body comosition of each subject. The scanning software (version 5.56) is aroriate for the weight range of our study subjects, and the accuracy of the fat mass and bone mineral content measurements is indeendent of ubertal develoment (29). Fat-free mass, in kilograms, was the difference between body weight and fat mass. Because skeletal bone mass, a nonmetabolic comonent of fat-free mass, is higher in African-American girls than in girls (30), soft lean tissue mass was obtained by subtracting bone mass from fat-free mass as follows (31): soft lean tissue mass (kg) = (fat-free mass) - (1.9 x bone mineral content). Energy intake At the laboratory, each subject received instructions from a dietitian on the aroriate comletion of a 3-day food record at home, including one weekend day. Each subject racticed the rocedure during her stay in the resiration chamber. These instructions also were given to the arent(s). Energy intake was calculated from the food records using the

3 908 WONGETAL. JCE & M 1999 Vol 84 No 3 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 exenditure in children, adolescents, and adults, whereas fat mass was only a minor contributor to energy exenditure in obese subjects (32, 33), all energy exenditure measurements were normalized to soft lean tissue mass (the mathematical ratio method) before statistical analysis. A f test was used to comare ethnic grous, with resect to age, hysical characteristics, body comosition, V0 2max ' energy intake, and all measures of energy exenditure. Because Tanner stages of ubertal develoment are not continuous variables, x-square was used to comare grous on sexual maturity. Because the mathematical ratio method has been shown to yield erroneous conclusions, regarding differences in energy exenditure (34), analysis of covariance also was used to determine the effect of race on all measures of energy exenditure, while controlling for soft lean tissue mass. Interactions between covariates and race were assessed. All statistical analyses were erformed using standardized software (SPSS for Windows, version 7.5.1, SPSS, Inc., Chicago, IL). Results Age, hysical characteristics, sexual maturity, and energy intake of study subjects Age, hysical characteristics, sexual maturity, and energy intake of the two grous are given in Table 1. The African American and girls were well matched for age, body weight, height, and BM!. The African-American girls, however, were sexually more mature than the girls. Neither the total energy intake, estimated from the 3-day food records, nor the calorie intakes of the macronutrients (exressed as ercentages of total energy intake) were Significantly different between the two grous. V0 2mox and body comosition of study subjects As shown in Table 2, the Y0 2max of the African-American girls was significantly lower than those of the 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 girls. No difference in fat mass, exressed either in absolute kilograms or in ercentage of body weight, was observed between the two grous. Differences in rates ofenergy exenditure, at rest, between the African-American and girls Sleeing energy exenditure and basal metabolic rate of the African-American and girls are summarized in Table 3. All calorimetric measures of energy exenditure, 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 girls. The racial differences in the calorimetric measures of energy exenditure remained significant after inclusion of sexual maturity and/or Y0 2max in the analysis of covariance. Fat mass was not included in the analysis because it was not different between the two grous, 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 exenditure were not affected by the size of soft lean tissue mass, the stages of ubertal develoment, or hysical fitness. Differences in free-living energy exenditure and energy exended for hysical activity, between the African American and girls Total energy exenditure and energy exended for hysical activity under free-living conditions (measured by the doubly labeled water method) are summarized in Table 4. The isotoe dilution saces (NH' No) were higher in the African-American girls than in the girls, whereas the fractional turnover rates of 2H and 18 0 were higher among the girls than in the African-American girls. No significant differences were observed in the 24-h RQ or UN rate between the two grous. Total energy exenditure and energy exended for hysical 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 girls. The racial differences in total energy exenditure and energy exended for hysical activity remained significant after inclusion of sexual maturity and/or Y0 2max 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 reorted in the National Health Examination Survey, Cycle II ( ) and the latest data recorded by the National Health and Nutrition Examination Survey ( ), the most dramatic increases in overweight have occurred in African-American girls (4). From 1963 to 1991, a TABLE max and body comosition of and African-American subjects African -American max' mukg. min 38.0:!:: :!:: <0.01 Body comosition Bone mineral content, kg 1.75 :!:: :!:: Bone mass, kg 3.32 :!:: :!:: Fat mass, kg 15.4 :!:: :!:: Fat mass, % 27.9:!:: :!:: Fat free mass, kg 35.6:!:: :!:: Soft lean tissue mass, kg 32.3 :!:: :!:: o Mean :!:: SD.

4 RACIAL DIFFERENCES IN ENERGY EXPENDITURE 909 TABLE 3. Energy exenditure measured by whole-room indirect calorimetry of and African-American subjects a Variables b African-American Total sleeing energy exenditure kcaukg sltm. d 40.2:!: :!: 4.0 <0.01 kcavd adjusted for sltm C 1306:!: :!: Basal metabolic rate kcaukg sltm. d 43.5:!: :!: 4.3 < 0.01 kcavd adjusted for sltm C 1412 :!: :!: " Values are mean:!: SD and P value by Student t test unless indicated otherwise. b Abbreviations: sltm, soft lean tissue mass. C Mean :!: SD and P value after adjusting for soft lean tissue mass by analysis of covariance. TABLE 4. Total energy exenditure and energy exended for hysical activity under free-living conditions measured by the doubly labeled water method" Variables b African-American NH,mol 1634 :!: :!: 296 <0.04 No, mol 1597 :!: :!: 285 <0.06 kh' d :!: :!: <0.02 ko,d :!: :!: RQ :!: :!: UN' g/day 9.0:!: :!: Free-living energy exenditure kcaukg sltm. d 84.9:!: :!: 19.1 < 0.02 kcavd adjusted for sltm C 2818 :!: :!: 722 < 0.03 Energy exended for hysical activity kcaukg sltm. d 36.5:!: :!: 16.5 <0.03 kcavd adjusted for sltm C 1271 :!: :!: 637 < 0.02 a Values are mean :!: SD and P value by Student t test unless indicated otherwise. b Abbreviations: NH, hydrogen isotoe dilution sace; No, oxygen isotoe dilution sace; kh' fractional turnover rate ofhydrogen; ko, fractional turnover rate of oxygen; RQ, resiratory quotient; UN, urinary nitrogen excretion rate; sltm, soft lean tissue mass. C Mean :!: SD and P value after adjusting for soft lean tissue mass by analysis of covariance. 150% increase in overweight was observed in African-American girls between 6 and 11 yr of age, and an 80% increase was reorted for African-American girls between 12 and 17 yr of age. During the same eriod, there was a Significantly lower (35%) increase in overweight among girls 6-17 yr of age. Because overweight children are at high risk of becoming overweight adults (7), a request for roosal (HL ) was released by the National Heart, Lung, and Blood Institute on Aril 17, 1998 to look for ways to revent excessive weight gain during adolescence in African-American girls through modifications in diet and hysical activity. Our data (Table 3), together with those reorted recently by Kalan et ai. (8), Morrison et ai. (9), and Yanovski et at. (10), clearly demonstrate the existence of a lower basal energy exenditure in reubertal and ubertal African-American girls, comared with girls. In this study, the sleeing energy exenditure and basal metabolic rate of the African-American girls were 62 and 78 kcal!day, resectively, lower than those of the girls. Although Ravussin et at. (12) observed a direct relationshi between a lower resting metabolic rate and later weight gain in 95 southwestern American Indian adults, over a eriod of 2-4 yr, the same grou reorted 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 eriod of 4 yr, Weinsier et ai. (13) reorted that the small differences in basal energy exenditure recorded were insufficient to account for later weight gain. However, the authors (13) were able to detect a significant relationshi between lower self-reorted hysical activity and weight gain in these women. Although soft lean tissue mass is the major determinant of energy exenditure (32, 33), Tanner stages of ubertal develoment were included in the analysis because the African-American girls were sexually more mature than the girls, in site of their similar chronological ages and hysical 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 ubic hair develoment is 1-2 yr earlier in African American girls than in girls (35). More imortantly, the magnitude of the differences in energy exenditure between the two ethnic grous 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 ubertal develoment has no effect on energy exenditure in children and adolescents after controlling for fat-free mass. As shown in Table 2, the V0 2max of the African-American girls was 15% lower than that of the girls. This result is similar to that reorted by Trowbridge et ai. (36). Inclusion of V0 2max in the analysis did not change the outcome, confirming that soft lean tissue mass is the major determinant of energy exenditure. The lower V0 2max observed in the African-American girls might be related to a lower ercentage of tye I fibers in their skeletal muscle, comared with s. African-American men have been shown to have a lower ercentage of tye I fibers than men (37), and their V0 2max has been shown

5 910 WONGETAL. JCE & M 1999 Vol 84 No 3 to be highly correlated with the ercentage of tye I fibers in their skeletal muscle (38). However, a muscle biosy, which was not done in this study, would be required to confirm this relationshi in African-American girls. Our results (Table 4) clearly demonstrated that energy exended for hysical activity under free-living conditions was significantly lower in the African-American girls than in the girls. Therefore, the lower level of hysical activity in the African American girls might have contributed to their lower aerobic fitness level. As shown in Table 4, the average total energy exenditure and energy exended by ubertal African-American girls for hysical activity under free-living conditions were, resectively, 410 and 462 kcal!day lower than the girls' rates, after adjustment of soft lean tissue mass, by analysis of covariance. The magnitude of the difference was aroximately 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 exenditure and energy exended for hysical activity, under free-living conditions, between reubertal African-American and girls. Their inability to detect a significant difference between the two ethnic grous might have been attributable to an insufficient number of study subjects (18 and 27 African-American girls). Because a lack of hysical activity has a ositive correlation with excessive weight gain (13, 39), and greater increases in adiosity have been documented in ubertal African American girls than in girls (40), the substantially lower total energy exended for hysical activity, under free-living conditions, in the ubertal African-American girls suggests that they are at increased risk of excessive fat gain, comared with the girls. Therefore, any rograms to minimize or revent overweight in African-American women must take into account the lower energy exenditure for hysical activity in this oulation during childhood, as well as in adulthood. Secifically, this study suggests that greater caloric restriction and hysical activity are indicated for African-American girls than for girls. Our subjects were recruited from middle-income families. It has been shown that children of low socioeconomic status have lower levels of hysical activity and higher body weight (41 ). Therefore, it is ossible that energy exenditure for hysical 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, articularly in African-American girls of low socioeconomic status, are needed to evaluate the efficacy of increasing hysical activity to control excessive weight gain and the ability to sustain ositive hysical 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. ]. Hoyle in the Pediatric Deartment of Kelsey-Seybold West Clinic; Dr. M. desvignes-kendrick, Director of the City of Houston Health and Human Services Deartment; Ms. X. Earlie, Director of Sciences of the Aldine Indeendent School District; Ms. S. Wooten, rincial at the Teague Middle School; Dr. B. Shargey, dean of instruction, and Ms. C. C. Collins, rincial 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. ShyaiJo-and Ms.]. Pratt, for the body comosition measurements; Mrs. L. L. Clarke and Mr. S. Zhang, for the isotoe ratio measurements; and to Ms. L. Loddeke, for editorial assistance in the rearation of the manuscrit. References 1. van Hallie TB Health imlications of overweight and obesity in the United States. Ann Intern Med. 103: Bray GA Comllcations of obesity. Ann Intern Med. 103: Kuczmarski RJ, Flegal KM, Cambell SM, Johnson CL Inc reasing revalence of overweight among US adults.the National Health and Nutrition Examination Survey, 1960 to JAMA. 272: Troiano RP, Flegal KM, Kuczmarski RJ, Cambell SM, Johnson CL Overweight revalence and trends for children and adolescents. Arch Pediatr Adolesc Med. 149: Kumanyika S Obesity in black women. Eidemiol Rev. 9: Kumanyika SK Obesity in minority oulations: an eidemiologic assessment. Obes Res. 2: Serdula MK, Ivery D,Coates RJ, Freedman OS, Williamson OF, Byers T Do obese children become obese adults? A review of the literature. 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New York: Academic Press; Bruce RA, Kusumi F, Hosmer D Maximal oxygen intake and nomograhic assessment of functional aerobic imairment in cardiovascular disease. Am Heart J. 85: Moon JK, Vohra FA, Jimenez OSV, Puyau MR, Butte NF Closed-loo control of carbon dioxide concentration and ressure imroves resonse of room resiration calorimeters. J Nutr. 125: Schofield WN Predicting basal metabolic rate, new standards and review of revious work. Hum Nutr :Clin Nutr. 39C: Weir JB New methods for calculating metabolic rate with secial reference to rotein metabolism. J Physio!. 109: Wong WW, Lee LS, Klein PD Deuterium and oxygen-18 measurements on microliter samles of urine, lasma, saliva, and human milk. Am J Clin Nutr. 45: Wong WW, Clarke LL, Llaurador M, Klein PD A new zinc roduct for the reduction of water in hysiological fluids to hydrogen gas for 2H / IH isotoe ratio measurements. 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6 RACIAL DIFFERENCES IN ENERGY EXPENDITURE Jensen CL, Butte NF, Wong WW, Moon JK Determining energy exenditure in re term infants: comarison of 2H2 'B O method and indirect calorimetry. Am J Physiol. 263:R685--R Shyailo RJ, Posada JKJ, Ellis KJ Whole-body hantoms with anthroomorh.ic-shaed skeletons for evaluation of dual-energy x-ray absortiometry measurements. Al Radiat [sot. 49: Ellis KJ, Abrams SA, Wong WW Body comosition of a young, multiethnic female oulation. Am J Clin Nutr. 65:724-73l. 3l. Snyder WS, Cook MJ, Nasset ES, Karhausen LR, Howells GP, Titon IH Weights of organs and tissues of reference man. In: Reort of the Task Grou on Reference Man. 1st ed. New York: Pergamon Press; Molnar D, Schutz Y The effect of obesity, age, uberty and gender on resting metabolic rate in children and adolescents. Eur J Fediatr. 156:376-38l. 33. Cunningham JJ Body comosition as a determinant of energy exenditure: a synthetic review and a roosed general rediction equation. Am J Clin Nutr. 54: Poehlman ET, Toth MJ Mathematical ratios lead to surious conclusions regarding age- and sex-related differences in resting metabolic rate. Am JClin Nutr. 61: Herman-Giddens ME, Siora EJ, Wasserman RC, et at 1997 Secondary sexual characteristics and menses in young girls seen in office ractice: a study from the Pediatric Research in Office Settings Network. Pediatrics. 99: Trowbridge CA, Gower BA, Nagy TR, Hunter GR, Treuth MS, Goran MJ Maximal aerobic caacity in African-American and reubertal children. Am J Physiol. 273:E809-E Ama PFM, Simoneau JA, Boulay MR, Serresse 0, Theriault G, Bouchard C Skeletal muscle characteristics in sedentary Black and males. J Al Physiol. 61: l. 38. Ivy JL, Costill DL, Maxwell BD Skeletal muscle determinants of maximum aerobic ower in man. Eur J Al Physiol. 44: Dietz WH, Gortmaker SL Factors within the hysical environment associated with childhood obesity. Am J Clin Nutr. 39: Kimm SYS, Barton BA, Obarzanek E, Crawford P Changes in adiosity in a biracial cohort during uberty: NHLBI growth and health study. Can J Cardiol. 13:218B. 4l. Filozof C, Zuckerfeld R, Berguella AM, Saenz S, Veiga G, Gonzalez C Higher relative weight in kids of lower socioeconomic grous is associated with lower levels of hysical activity and higher erceived stress. Obes Res. 5:115. Euroean Federation of Endocrine Societies 3rd Postgraduate Course in Molecular and Cellular Endocrinology July 7-11, 1999 Munster, Germany Toics: Introductory lectures on hormone action, selected endocrine toics, endocrinology and reroduction and develoment, workshos on molecular and cellular techniques in endocrinology, technology lectures. Deadline for registration: May 1, Number of registrations will be limited to 120 on a first-comefirst-serve-basis. Registration fee: 150 EURO/294 DM. The final rogramme and the registration form are available at the Course Secretariat: Institute of Reroductive Medicine, Domagkstr. 11 D Miinster, Germany. Tel: +49/ ; Fax: +49/ ; Bbahnes@uni-muenster.de