Effect of diet on insulin sensitivity and energy balance

描述(由申请人提供)：这项研究提案的广泛、长期目标是通过降低患2型糖尿病的风险来改善老年人的健康和福祉。该项目的具体目的是检查随机12周的低脂肪/简单碳水化合物饮食，包括有氧运动训练和不进行有氧运动训练，对糖耐量受损的老年受试者的体重、能量平衡和胰岛素敏感性的影响。初步数据表明，在没有限制能量的情况下，食用低脂肪/复合碳水化合物饮食会导致体重减轻和胰岛素敏感性的改善。我们假设，用简单的碳水化合物而不是复杂的碳水化合物取代膳食脂肪将在健康方面产生类似的改善。36名年龄在55-80岁之间、糖耐量受损的超重男性和女性将被随机分为三组。第1组将接受控制饮食(类似于基线摄入量)，第2组将接受低脂/简单碳水化合物饮食(17%脂肪、16%蛋白质、67%碳水化合物、9g纤维/1000kcal)，第3组将接受相同的低脂饮食并加入有氧运动训练计划(每周4d，80%VO2，)。身体成分将使用空气置换体积描记仪测量，能量和常量营养素代谢将使用全房量热法和从头脂肪生成来测量，胰岛素敏感性将使用正常血糖-高胰岛素钳进行测量。鉴于2型糖尿病在美国老年人群中的患病率越来越高，该项目的完成将更清楚地确定对老年人健康具有最大潜在积极影响的具体饮食和运动干预措施。

DESCRIPTION (provided by applicant): The broad, long-term objective of this research proposal is to improve the health and well being of the elderly via decreased risk for type 2 diabetes. The specific aim of the project is to examine the influence of an ad libitum 12- week low-fat/simple-carbohydrate diet, with and without aerobic exercise training, on body mass, energy balance, and insulin sensitivity in older subjects with impaired glucose tolerance. Preliminary data indicate that consumption of a low-fat/complex-carbohydrate diet, with no attempt at energy restriction, results in loss of body weight and improvement in insulin sensitivity. We hypothesize that replacement of dietary fat with simple rather than complex-carbohydrates will result in similar improvements in health. Thirty-six overweight men and women aged 55-80 years with impaired glucose tolerance will be randomized into one of three groups. Group 1 will receive a control diet (similar to baseline intake), group 2 will receive a low-fat/simple-carbohydrate diet (17% fat, 16% protein, 67% carbohydrate, 9g fiber/1000kcal), and group 3 will receive an identical low-fat diet and be placed in an aerobic exercise training program (4d/week, 80% VO2ma,). Body composition will be measured using air displacement plethysmography, energy and macronutrient metabolism will be measured using whole room calorimetry and de novo lipogenesis, and insulin sensitivity will be measured using a euglycemic-hyperinsulinemic clamp. Given the increasing prevalence of type 2 diabetes in the elderly U.S. population, completion of this project will more clearly define the specific dietary and exercise interventions that have the greatest potential positive impact on health in older individuals.