A controlled feeding study concluded that diets with low glycemic index (GI) of dietary carbohydrate did not result in improvements in insulin sensitivity, lipid levels, or systolic blood pressure in overweight adults. The 5 week randomized crossover-controlled feeding trial included 163 overweight adults (systolic blood pressure, 120-159 mm Hg) between April 1, 2008 and December 22, 2010 in the US. The participants were given 4 complete diets: (1) A high-GI (65% on the glucose scale), high-carbohydrate diet (58% energy); (2) a low–GI (40%), high-carbohydrate diet; (3) a high–GI, low-carbohydrate diet (40% energy); and (4) a low-GI, low-carbohydrate diet. Each diet was based on a healthful DASH-type diet. The 5 primary outcomes were insulin sensitivity, determined from the areas under the curves of glucose and insulin levels during an oral glucose tolerance test; levels of low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglycerides; and systolic blood pressure. At high dietary carbohydrate content, the low– compared with high–GI level decreased insulin sensitivity; increased LDL cholesterol; and did not affect levels of HDL cholesterol, triglycerides, or blood pressure. At low carbohydrate content, the low– compared with high–GI level did not affect the outcomes except for decreasing triglycerides. In the primary diet contrast, the low–GI, low-carbohydrate diet, compared with the high–GI, high-carbohydrate diet, did not affect insulin sensitivity, systolic blood pressure, LDL cholesterol, or HDL cholesterol but did lower triglycerides. The findings suggest that GI or load of carbohydrates is less relevant than an emphasis on the overall dietary pattern. The GI is quantified according to the amount 50 grams of its carbohydrate compared with 50 grams of glucose increased blood glucose over the course of 2 hours. Two previously reported meta-analyses showed benefits for a low GI diet in people with type 2 diabetes. The DASH diet and Mediterranean-style diet have been identified as heart healthy. Both diets are plant focused, with an emphasis on fruits, vegetables, whole grains and nuts and the DASH diet also includes low-fat and nonfat diary, lean meats, fish and poultry. Source: http://jama.jamanetwork.com/article.aspx?articleid=2040224一个对比饮食研究的结论是膳食中碳水化合物的血糖指数（GI）低并未改善胰岛素敏感性，血脂水平，或超重成年人的收缩压。 该项5周的随机交叉对照饮食试验包括了2008年4月1日至2010年12月22日期间163名超重的美国成年人（收缩压120-159毫米汞柱）。参与者分别给予4套完整的膳食：（1）高GI（相当于65％葡萄糖的水平），高碳水化合物饮食（58％的能量）; （2）低GI（40％），高碳水化合物饮食; （3）高GI，低碳水化合物饮食（40％能量）;和（4）低GI，低碳水化合物饮食。每套膳食均基于健康的DASH式饮食。 5项主要指标包括对胰岛素的敏感性（根据口服糖耐量试验过程中血糖和胰岛素水平的曲线下面积而确定），低密度脂蛋白（LDL）胆固醇，高密度脂蛋白（HDL）胆固醇和甘油三酯的水平，以及收缩压。对高碳水化合物膳食，低GI水平相比高GI水平胰岛素敏感性降低，增加LDL胆固醇，而HDL胆固醇，甘油三酯，或血压水平未受影响。对低碳水化合物膳食，低GI水平相比高GI水平除了降低甘油三酯外未影响其它指标。主要膳食对比，低GI，低碳水化合物饮食，与高GI，高碳水化合物饮食相比，并未影响胰岛素的敏感性，收缩压，LDL胆固醇，或HDL胆固醇，但确实降低甘油三酯。这些发现提示GI或碳水化合物摄入量不如强调整体膳食结构那么重要。GI是根据膳食中50克碳水化合物与50克葡萄糖相比在2小时的过程中所增加的血糖而确定的。两个先前报道的荟萃分析表明低GI的饮食对患有2型糖尿病者有益。 DASH饮食和地中海风格的饮食已被确定为有益于心脏健康。这两种饮食均着重于植物，重点是水果，蔬菜，全谷类和坚果；DASH饮食还包括低脂和脱脂奶类，瘦肉，鱼和家禽。来源：http://jama.jamanetwork.com/article.aspx?articleid=2040224
