ENERGY EXPENDITURE, DIET AND BODY FAT IN CHILDREN

肥胖在美国印第安人儿童中非常普遍，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和减少膳食脂肪摄入量来增加能量消耗应该会减缓体脂增加的速度，但似乎儿童从青春期前到青春期后的成熟实际上减少了他们的体力活动。几项研究表明，女性活动量的下降比男性更严重，非白人比白人更严重；然而，其他研究并不支持这些发现。此外，目前还没有关于美洲印第安人儿童的数据，这是一个风险最高的群体。此外，关于体重或体脂与能量摄入量或膳食脂肪摄入量之间的关系也有不一致的报道。问题的核心是难以准确衡量自我报告的体力活动和饮食摄入量。在大规模研究中使用准确的自我报告测量是必要的，这些研究需要调查体力活动和饮食摄入与疾病之间的关系。《2000年健康人：国家健康促进和疾病预防目标》包括七项目标，强调增加儿童和青少年的体育活动。为了支持2000年的健康人，美国国立卫生研究院：国家心脏、肺和血液研究所发布了一份题为《体力活动与心肺健康》的计划公告(PA-95-004)，以征集与心血管疾病风险因素相关的体力活动领域的明确研究。本研究采用纵向和横断面相结合的研究方法，对现有的儿童青少年体力活动和膳食摄入量自报方法进行改进，并以双标记水(DLW)测量的总能量消耗(TEE)为标准评价其有效性。然后，我们将使用这些方法来测量两个年龄段的男性和女性美洲印第安人儿童(8-10岁和11-13岁)在基线和两年后的体力活动和饮食摄入量，并进行两组临时测量。TEE从基线到两年随访的变化也将使用DLW和TriTrac加速度计进行测量。估计身体脂肪百分比的公式将针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体力活动和膳食摄入量的工具来填补现有空白，并将提供这些变量随时间的变化在同一儿童中的纵向数据，并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.