There are distinct gaps in our understanding of the link between obesity and/or fat distribution and increased risk of disease in adolescent children, particularly among different ethnic groups. Prior studies have not used accurate or precise techniques for measurement of body fat and fat distribution and have examined limited risk factors for obesity-related disease. We propose to recruit 200 Caucasian and African American adolescents and use state-of-the-art techniques for measuring total body fat (dual energy X-ray absorptiometry), intra-abdominal adipose tissue (computed tomography), and physical activity related energy expenditure (combination of doubly labeled water and indirect calorimetry) to examine whether there is a fat deposit in particular (i.e. intra-abdominal adipose tissue) that is more strongly related to increased risk of disease. We will examine blood pressure and circulating lipid and lipoprotein levels as risk factors for the development of cardiovascular disease and fasting insulin, glucose intolerance, and insulin sensitivity (using Bergman Minimal Model Technique) as risk factors for the development of non-insulin dependent diabetes mellitus. We hypothesize that intra-abdominal adipose tissue will be the strongest correlate of risk factors for disease and that the relationship between intra-abdominal adipose tissue and increased risk of disease will not be significantly influenced by factors such as gender, age, hormone status, ethnic background, or total body fat mass. It is also hypothesized that the effects of physical activity and physical fitness on risk of disease will be mediated through their effects on intra-abdominal adipose tissue. Finally, we will use the collected data to develop alternative clinical and research tools for estimating intra-abdominal adipose tissue in adolescents. Our unifying hypothesis is that the amount of intra-abdominal adipose tissue is the specific phenotype relating obesity to increased risk of disease in adolescents, and that the effects of ethnicity, gender, hormonal status, and physical inactivity on risk of disease are mediated through their effects on intra-abdominal adipose tissue. These findings will imply that prevention and intervention programs aimed at reducing long term risk of disease should be focused on intra-abdominal adipose tissue.
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