Overall Goal: Project 1 will determine ethnic differences in body fat distribution, insulin resistance, insulin-like growth factors and binding proteins, inflammatory markers and oxidative stress in overweight African American and Hispanics children during the critical period of adolescent growth. Thereafter, we will examine the impact of strength training as a therapeutic intervention to improve these risk factors. We build upon previous work to hypothesize that hyperinsulinemia in African American youth is associated with important metabolic differences that could increase long-term cancer risk. Specific Aims: (1) To determine the contribution of body fat compartments (visceral fat, muscle fat and liver fat) and adipokines to insulin resistance in African American and Hispanic youth;(2) To examine differences in metabolic compensation to insulin resistance between African American and Hispanic youth;(3) To examine the influence of body fat, insulin resistance and ethnicity on markers of lipid peroxidation and oxidative stress, and (4) To determine the effects of a randomized strength training intervention on potential mechanistic factors linking obesity to cancer risk. Design: Crosssectional (40 African-Americans vs 40 Hispanics) and 16-week strength training program in which obese adolescents are randomly assigned to nutrition education or nutrition education plus supervised strength training. Dependent Variables: Major outcome variables include: Insulin sensitivity and insulin response to glucose by intravenous glucose tolerance test;whole body composition by (dual energy Xray absorptiometry);visceral fat, liver fat and muscle fat by magnetic resonance spectroscopy;blood draws for measures of oxidative stress, lipid peroxidaton, plasma lipids and genetic admixture;physical activity by accelerometry. Significance: Project 1 will shed new light on differences in metabolic risk factors for cancer between African Americans and Hispanics as well as their response to strength training. The contrast between African Americans and Hispanics is of particular interest because these groups share similar pre-disposition to obesity, greater insulin resistance and risk for type 2 diabetes, but for the major types of cancer, African Americans have substantially greater risk than Hispanics. Furthermore, this study will provide new information regarding the impact of strength training as an anti-obesity and anti-carcinogenic intervention in "at risk" minority adolescents.