There are distinct gaps in our understanding of the link between obesity and/or fat distribution and increased disease risk in adolescent children. We are conducting a 5-year longitudinal study to examine the temporal relationships between changes in body fat, body fat pattern, insulin sensitivity, lipid profile, physical activity, and sex hormones during adolescent growth. We have recruited a cohort of 120 African-American and Caucasian children and are performing annual measures of total body fat (4-compartment model), body fat pattern (dual energy X-ray absorptiometry, computed tomography), physical activity (combination of doubly labeled water and indirect calorimetry), whole-body insulin sensitivity (Bergman minimal model) as well as blood pressure and circulating lipid and lipoprotein levels as risk factors for cardiovascular disease. The hypotheses of the study are that: 1) The relationship between obesity and disease risk in Caucasian and African American adolescents is due specifically to the accumulation of visceral fat; 2) Physical inactivity, total body fat, and sex hormone levels contribute to the development of visceral fat during adolescence, which leads to the development of insulin resistance which in turn leads to the development of dyslipidemia. The strength of these cause and effect relationships will not be significantly influenced by ethnicity, or gender; and, 3) Visceral fat can be accurately predicted from anthropometry, and more accurate equations can be developed by inclusion of total abdominal fat by dual energy X-ray absorptiometry. Initial cross-sectional analysis have characterized visceral fat in pre- pubertal children and examined the influence of gender ethnicity, and body composition. In the next year we will continue to collect longitudinal data on this cohort and begin to analyze the cross-sectional and longitudinal hypothesis laid out above.
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