IMPACT OF TOTAL BODY FAT IN SEDENTARY HISPANIC ADOLESCENTS WITH NORMAL BMI

该子项目是利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得主要资金， 因此可以在其他CRISP条目中表示。列出的机构是 中心，不一定是研究者的机构。 国家健康和营养检查调查（NHANES II和III）报告称，儿童超重和肥胖以及与肥胖有关的疾病的流行率不断上升。这是一个严重的公共卫生问题，需要进行研究以确定哪些因素导致肥胖，以及可以使用哪些策略来预防和治疗肥胖及其后果。为解决这些问题而进行的大多数研究都需要对肥胖和消瘦的受试者进行比较。为了提供准确的结论，“瘦”和“肥胖”的定义必须绝对明确。区分瘦与肥胖受试者的最常用标准是体重指数（BMI），即体重（kg）/身高（m2）。然而，BMI在正常年龄范围内可能导致异质组，包括低和高体脂百分比、低和高内脏脂肪以及低和高肝脏脂肪含量的受试者。所有这些因素都可能混淆结果和结论。 在本方案中，我们将探讨是否有相关性之间的身体脂肪百分比（通过DXA测量），内脏肥胖（通过MRI测量），肝脏脂肪含量（通过MRI测量）和胰岛素敏感性（通过空腹胰岛素和口服葡萄糖耐量试验（OGTT）评估）（低于第85百分位数，即计划年龄组中的25 kg/m2），体脂百分比等于或高于女孩27%和男孩25%。这些结果将与我们正在进行的研究（H-11954）的结果进行比较，包括严格的瘦和肥胖受试者。从该拟定方案和正在进行的研究中收集的信息将使我们能够确定BMI、体脂百分比和脂肪分布对青少年胰岛素敏感性和葡萄糖稳态的影响，这反过来将为优化肥胖研究中的筛选方法提供指导。 总体假设 使用BMI作为定义瘦受试者的唯一标准导致具有正常和高体脂百分比的受试者的混合。具有高体脂百分比的受试者包含胰岛素敏感性受试者和胰岛素抗性受试者。胰岛素敏感性与内脏脂肪含量有关。 1.在具有正常BMI但高体脂百分比的青少年群体中，一些受试者将具有低内脏脂肪含量和一些高内脏脂肪含量，并且该群体将包含胰岛素敏感和胰岛素抵抗受试者。 2.在BMI正常、体脂百分比高的青少年中，胰岛素敏感性与内脏脂肪含量相关。 3.在BMI正常和体脂百分比高的青少年中，内脏脂肪与肝脏脂肪含量相关。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The National Health and Nutrition Examination Surveys, NHANES II and III, report an increasing prevalence of overweight and obesity as well as of obesity related diseases in children. This is a serious public health problem necessitating research to determine which factors lead to obesity and which strategies could be used to prevent and treat obesity and its consequences. Most of the research conducted to address these issues requires comparison between obese and lean subjects. In order to provide accurate conclusions, the definition of "lean" and "obese" must be absolutely clear. The most routinely used criteria to distinguish lean from obese subjects is body mass index (BMI) i.e. weight in kg/ height in m2. However, a BMI within the normal range for age might result in heterogeneous groups, including subjects with both low and high body fat percentage, low and high visceral fat and low and high hepatic fat content. All of these factors might confound results and conclusions. In this protocol we will explore whether there is a correlation between body fat percentage (measured by DXA), visceral adiposity (measured by MRI), hepatic fat content (measured by MRI) and insulin sensitivity (assessed by fasting insulin and an Oral Glucose Tolerance Test (OGTT)) in adolescents with normal BMI (below the 85th percentile i.e. 25 kg/m2 in the planned age group) and body fat percentage equal to or above 27% in girls and 25% in boys. These results will be compared with those of our ongoing study (H-11954) including strictly lean and obese subjects Collectively the information from this proposed protocol and the ongoing study, will enable us to define the influence of BMI, body fat percentage and fat distribution on insulin sensitivity and glucose homeostasis in adolescents, which will in turn provide guidelines for optimizing screening methods in studies on obesity. Overall hypothesis Using BMI as the only criteria to define lean subjects results in a mix of subjects with both normal and high body fat percentage. Subjects with high body fat percentage contain both insulin sensitive and insulin resistant subjects. Insulin sensitivity is related to their visceral fat content. 1.In a population of adolescents with normal BMI, but high body fat percentage, some subjects will have low and some high visceral fat content, and this population will contain both insulin sensitive and insulin resistant subjects. 2.In adolescents with normal BMI and high body fat percentage, insulin sensitivity is correlated with visceral fat content. 3.In adolescents with normal BMI and high body fat percentage, visceral fat correlates with hepatic fat content.