ENERGY EXPENDITURE, DIET AND BODY FAT IN CHILDREN

肥胖在美国印第安儿童中非常普遍，增加了他们患心血管疾病、高血压和糖尿病的风险。虽然通过增加体力活动来增加能量消耗和减少饮食中脂肪的摄入应该会减缓身体脂肪增加的速度，但似乎随着儿童从青春期前到青春期后的成熟，他们的体力活动实际上会减少。几项研究表明，女性活动的减少比男性更大，非白人比白人更大；然而，其他研究并不支持这些发现。此外，没有关于美国印第安儿童的数据，这是一个风险最大的人群。此外，关于体重或体脂与能量摄入或膳食脂肪摄入之间的关系也有不一致的报道。问题的核心是难以准确测量自我报告的身体活动和饮食摄入量。准确的自我报告测量在大规模研究中是必要的，这些研究需要调查身体活动与饮食摄入和疾病之间的关系。《2000年健康人：全国促进健康和预防疾病目标》包括强调增加儿童和青少年体育活动的七项目标。为了支持“2000年健康人群”计划，美国国立卫生研究院：国家心脏、肺和血液研究所发布了一项题为“体育活动与心肺健康”的计划公告（PA-95- 004），征求在与心血管疾病风险因素相关的体育活动领域进行明确界定的研究。本研究采用纵向和横断面相结合的设计，对现有儿童和青少年体育活动和饮食摄入自我报告的最佳方法进行修改，并以双标签水（DLW）测量的总能量消耗（TEE）为标准评估其有效性。然后，我们将使用这些方法测量两个年龄组的美国印第安儿童（8-10岁和11-13岁）在基线和两年后的身体活动和饮食摄入量，并采用两组中期测量。从基线到两年随访的TEE变化也将使用DLW和TriTrac加速度计进行测量。估计体脂百分比的公式将对这一人群进行交叉验证。拟议的研究将通过改进现有的测量儿童和青少年身体活动和饮食摄入的工具来填补现有的空白，并将提供这些变量随时间变化的纵向数据，以及提供每个年龄和性别群体的横截面数据，以与现有文献进行比较。

Obesity is highly prevalent in American Indian children, increasing their risk for the development of cardiovascular disease, hypertension and diabetes. Although increasing energy expenditure, through increasing physical activity, and decreasing dietary fat intake should slow the rate of body fat gain, it appears that children actually decrease their physical activity as they mature from pre-to post-pubescence. Several studies have shown that the decline in activity is greater in females than in males, and greater in non-whites than in whites; however, other studies have not supported these findings. Further, there are no data available in American Indian children, which is a population at greatest risk. Additionally, inconsistencies have been reported with respect to the relationship between body weight or body fat and energy intake or dietary fat intake. At the heart of the problem is the difficulty in measuring self-reported physical activity and dietary intake accurately. Accurate self- report measures are necessary for use in the large scale studies that are required to investigate relationships between physical activity and dietary intake and disease. The Healthy People 2000: National Health Promotion and Disease Prevention Objectives include seven objectives emphasizing increasing physical activity in children and adolescents. In support of Healthy People 2000, the National Institutes of Health: National Heart, Lung and Blood Institute has published a Program Announcement (PA-95- 004)entitled, Physical Activity and Cardiopulmonary Health, to solicit well-defined studies in the area of physical activity related to cardiovascular disease risk factors. This study is a combined longitudinal and cross-sectional design in which we will modify the best existing methods for the self-report of physical activity and dietary intake in children and adolescents, and evaluate their validity using total energy expenditure (TEE) measured by doubly labeled water (DLW) as the criterion. We will then use these methods to measure physical activity and dietary intake in two age cohorts of male and female American Indian children (8-10-years and 11-13-years) at baseline and two years later, with two sets of interim measurements. Change in TEE from baseline to the two-year follow-up will also be measured using DLW and the TriTrac accelerometer. Equations for the estimation of percent body fat will be cross-validated for this population. The proposed study will fill an existing gap by improving existing instruments for the measurement of physical activity and dietary intake in children and adolescents, and will provide longitudinal data on change in these variables in the same children over time, plus provide cross-sectional data for each age and gender group to compare to the existing literature.