Energy balance, body composition, and puberty in children and adolescents: importance of ethnicity Barbara A. Gower, PhD, and Paul B. Higgins, BS Among children and adolescents in the United States, both obesity and type 2 diabetes are more prevalent in black and Hispanic subjects. This review summarizes research to date regarding ethnic differences in body composition, body fat distribution, metabolism, pubertal timing, and endocrine status that may contribute to observed disparities in obesity and associated diseases. Research indicates that black children and adolescents have greater bone mineral content and bone mineral density than their white, Hispanic, and Asian counterparts. Similar results have been found at and during puberty. Cross-sectional studies have yielded discrepant results regarding ethnic differences in soft tissue mass. It appears that white children have greater intra-abdominal adipose tissue than black children. Studies on differences in adiposity between black and white subjects report conflicting results. Data do indicate greater fat mass among Hispanic children and adolescents versus white and black subjects. In most studies undertaken, circulating insulin-like growth factor I levels are elevated in black versus white and Hispanic prepubertal children. However, variation in circulating insulin-like growth factor I (free or bound) does not explain ethnic differences in body composition. Insulin, particularly after a glucose challenge, is higher among black versus white subjects, and may be responsible for lower rates of lipolysis and perhaps greater adipose tissue accrual among black subjects. Limited data suggest that estradiol is higher in black versus white subjects. Numerous data indicate that resting energy expenditure is lower among black versus white subjects. Data regarding physical activity are less clear but indicate that at least some populations of black children are less physically active than white children. Whether ethnic differences in resting or physical activity-related energy expenditure contribute to differences in obesity or disease risk remains to be determined. Curr Opin Endocrinol Diabetes 2003, 10:9–22 © 2003 Lippincott Williams & Wilkins, Inc. Among children and adolescents in the United States, both obesity [1] and type 2 diabetes [2] are more preva- lent among certain ethnic minorities, such as black people and people of Hispanic or Latin descent. The reasons for the increasing rate of obesity among all US children are not entirely clear and will not be discussed in depth in this review. However, children of different ethnic backgrounds have been observed to differ with respect to body composition, body fat distribution, me- tabolism (resting energy expenditure [REE] and maxi- mal oxygen consumption), pubertal timing, and endo- crine status (concentrations of certain hormones). These differencesmaycontributetoobservedethnicdisparities inobesity,disease,anddiseaseriskfactors.Furthermore, the dramatic hormonal and metabolic changes that occur duringthepubertaltransitionmaymagnifyorexacerbate aspects of physiology that contribute to risk for obesity and disease, and that may differ with ethnicity. The goal of this review article is to summarize what has been published regarding ethnic differences in body composition, ethnic differences in aspects of the endo- crine system that may affect body composition, and eth- nicdifferencesinthecomponentsofenergybalance(en- ergy intake and energy expenditure) that may affect the risk for obesity. Particular attention is paid to the effect of puberty and associated physiologic changes on these measures. Because white and black people have been better represented in research studies than other ethnic groups, proportionately more information is available on these two groups and is included in this review; infor- mationonotherethnicgroupsisincludedwhenavailable and relevant. Body composition Growth velocity is greatly increased at puberty, precipi- tated by elevations in growth hormone, insulin, and an- drogen concentrations. As a result, significant changes in gross body composition and in the distribution of tissue massoccur.Increasesinshouldercircumferenceoccurin boys, and increases in hip circumference are observed in Department of Nutrition Sciences, Division of Physiology and Metabolism; and Clinical Nutrition Research Center, University of Alabama at Birmingham, Birmingham, Alabama, USA. Correspondence to University of Alabama at Birmingham, Department of Nutrition Sciences, 423 Webb Building, 1675 University Blvd., Birmingham, AL 35294-3360, USA; e-mail: bgower@uab.edu Current Opinion in Endocrinology & Diabetes 2003, 10:9–22 Abbreviations ABMD areal bone mineral density BMAD bone mineral apparent density BMC bone mineral content BMD bone mineral density BMI body mass index DXA dual-energy x-ray absorptiometry FFM fat-free mass IGF insulin-like growth factor IGFBP insulin-like growth factor binding protein IVGTT intravenous glucose tolerance test QCT quantitative CT REE resting energy expenditure Si insulin sensitivity VBMD volumetric bone mineral density ISSN 1068–3097 © 2003 Lippincott Williams & Wilkins, Inc. 9