DIETARY COMPOSITION, OBESITY, AND CARDIOVASCULAR RISK

冠心病（CHD）是导致人类死亡和残疾的主要原因之一。肥胖通过对血糖、脂蛋白和血压产生不利影响而增加冠心病的风险。人们一致认为，限制饮食中的饱和脂肪和胆固醇(C)有利于降低低密度脂蛋白（LDL）和降低冠心病风险，但对饮食的其他方面存在争议。我们拟对80名男性和女性（男性大于等于50岁，小于65岁）在空腹和非空腹状态（餐后4小时）检查符合国家胆固醇教育计划第二步饮食标准的三种饮食对体重和组成以及冠心病危险因素（LDL C、HDL C、残余脂蛋白C、Lp(a) C、胰岛素、糖化血红蛋白、葡萄糖和血压）的影响。绝经后年龄小于65岁的女性，低密度脂蛋白C值大于等于130 mg/dI，体重指数大于等于28小于38 kg/m2。研究将分为四个阶段，前三个阶段提供所有食物和饮料，而第四阶段提供推荐饮食，但不提供。在第一阶段，所有受试者最初将被安排在平均等重的美国饮食5周(15%蛋白质，35%脂肪，15%饱和脂肪，15%单不饱和脂肪，15%脂肪，15%脂肪，15%蛋白质，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%脂肪，15%蛋白质。6%多不饱和脂肪，含150毫克胆固醇/1000卡路里和10克纤维/1000卡路里)。在第二阶段，受试者将被随机分配到三种饮食中的一种，这些饮食都含有15%的蛋白质，5%的饱和脂肪和60毫克的胆固醇/1000卡路里：1)高复合碳水化合物（CHO）： 15%的脂肪，5%的单一碳水化合物，5%的多元碳水化合物和70%的CHO（主要是相对较高的复合血糖指数），16克/1000卡路里的纤维，低膳食热量密度为1.10卡路里/克；2)高单糖：与饮食1相同，但脂肪含量为30%（15%单糖）和55% CHO， CHO具有高血糖指数和高热量密度，1.25卡/克；3)复合：与日粮2相同，只是升糖指数更低，日粮热量密度为1.10 g/1000 cal)。这些饮食将被随意提供，受试者可以在12周内使用200卡路里的砂锅菜调整他们的卡路里水平，从维持体重所需卡路里的66%到133%。然后，受试者将在第三阶段的受控环境下继续保持相同的饮食等重，再持续5周，然后在一年（第四阶段）的非受控环境下，他们将接受饮食指导和菜单，但不接受食物。体重和血压每周评估3次，血浆脂蛋白（LDL、HDL、残体和Lp[a]）、葡萄糖、糖化血红蛋白和胰岛素水平将在每个控制饮食期结束时以及长期随访期的第3、6、9和12个月时在空腹状态和进食状态分别评估3次和1次。此外，体重、身体能量消耗、体力活动、身体成分、人体测量学和代谢率将在所有阶段定期测量。我们的假设是，富含复合碳水化合物、低热量密度的限脂饮食和低热量密度和血糖指数的复合饮食比单脂肪、血糖指数和卡路里密度较高的Step 2饮食对冠心病危险因素、体重、体成分和能量消耗的影响更有利。

Coronary heart disease (CHD) is a major cause of death and disability in our society. Obesity increases CHD risk by adversely affecting glucose, lipoproteins, and blood pressure. There is consensus that dietary saturated fat and cholesterol (C) restriction is beneficial for low density lipoprotein (LDL) lowering and CHD risk reduction, but there controversy about other aspects of the diet. We propose to examine the effects of three diets meeting National Cholesterol Education program Step 2 diet criteria on body weight and composition and on CHD risk factors (LDL C, HDL C, remnant lipoprotein C, Lp(a) C, insulin, glycosylated hemoglobin, glucose, and blood pressure) in the fasting and nonfasting state (4 hours after a meal) in 80 men and women (men greater than or equal to 50 and less than 65 years of age, women postmenopausal and less than 65) with LDL C values greater than or equal to 130 mg/dI and a body mass index greater than or equal to 28 and less than 38 kg/m2. A four phase study will be conducted in which all food and drink is provided during the first 3 phases, while diet is recommended but not provided in the fourth phase. In phase 1, all subjects will initially be placed on an average isoweight U.S. diet for 5 weeks (15 percent protein, 35 percent fat; 15 percent saturated fat; 15 percent monounsaturated (mono) fat; 6 percent polyunsaturated (poly) fat, with 150 mg of cholesterol/1000 calories and 10 g/1000 cal. of fiber). For phase 2, subjects will then be equally randomized to one of 3 diets, all containing 15 percent protein, 5 percent saturated fat and 60 mg of cholesterol/1000 calories: 1) high complex carbohydrate (CHO): 15 percent fat, 5 percent mono, 5 percent poly, and 70 percent CHO (mainly complex with relatively high glycemic index), 16 g/1000 cal of fiber, and low dietary caloric density of 1.10 cal/gm; 2) high mono: identical to diet 1 except that the fat content will be 30 percent (15 percent mono) and 55 percent CHO with CHO of high glycemic index and high caloric density, 1.25 cal/gm; and 3) composite: identical to diet 2 except that there will be lower glycemic index and low dietary caloric density of 1.10 g/1000 cal). These diets will be given ad libitum, and subjects can adjust their calorie level using 200 calorie casseroles from 66 percent to 133 percent of calories needed to maintain weight, for a 12 week period. Subjects will then be continued on these same diets isoweight for an additional 5 weeks under controlled circumstances in phase 3, and then for one year (phase 4) under uncontrolled circumstances where they will receive dietary instruction and menus, but not food. Body weight and blood pressure will be assessed three times per week, and plasma lipoproteins (LDL, HDL, remnants, and Lp[a]), glucose, glycosylated hemoglobin, and insulin levels will be assessed three times in the fasting state and once in the fed state at the end of each controlled dietary period and at 3, 6, 9, and 12 months in the long-term follow-up period. In addition, body weight, body energy expenditure, physical activity, body composition, anthropometics, and metabolic rate will be measured at regular intervals during all phases. Our hypothesis is that the fat-restricted diet rich in complex carbohydrate and low in caloric density and the composite diet low in caloric density and glycemic index will have a more favorable effect on CHD risk factors, body weight, body composition and energy expenditure than the Step 2 diet higher in mono fat, glycemic index, and caloric density.