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3种减肥食谱效果各异

低脂饮食最易体重反弹 极低碳水化合物饮食效果好但难坚持
Three Weight-Loss Diets Yield Three Metabolic Effects
来源:EGMN 2012-06-27 14:30点击次数:201发表评论

波士顿儿童医院、新平衡基金会肥胖预防中心的Cara B. Ebbeling 博士报告,3种旨在维持减肥效果的饮食对肥胖和超重的年轻成人的代谢影响存在明显差异,而且其代谢效应独立于其所含热量的多少。这项研究发表在6月27日《美国医学会杂志》上。“这一研究结果对‘同等热量的不同食物会产生同样的代谢效应’的观念提出了挑战。”


Ebbeling 博士及其同事开展了控制进食研究,以比较3种维持减肥效果饮食对能量消耗、激素和代谢综合征成分的影响。他们第一步筛选出了681名年龄18~40岁、体重指数(BMI)≥27 kg/m2的候选受试者。其中仅有32人(17男、15女)符合入组标准且同意严格限制饮食。在这32名受试者中, 有21人完成了研究并被纳入数据分析。


在预试验阶段,受试者遵循标准的低热量饮食,达到体重降低12.5%的目标。同时进行详细的检查评估,确定每名受试者将体重维持在这一低水平所需的热量。受试者在体重下降10%~15%之后,开始遵循3种等热量饮食中的1种,为期4周,然后改为另一种, 4周后再改为最后1种饮食,坚持4周。


这3种饮食内容如下:(1)低脂饮食,糖负荷高,20%的热量来自蛋白质。这反映了通常推荐的饮食,即减少脂肪、增加全谷物,并含有多种蔬菜和水果;(2)低升糖指数饮食,糖负荷中等,20%的热量来自蛋白质。该饮食将部分谷物和含淀粉蔬菜改为其他蔬菜、豆类和水果。(3)极低碳水化合物饮食,糖负荷低, 30%的热量来自蛋白质。这是仿照Atkins饮食设计的。


在遵循这3种维持低体重饮食期间,受试者的体重无显著差异,总体力活动、中高强度活动时间、主观饥饿感和幸福感也相似,血压水平也未出现波动。


在采取这3种饮食期间,静息热量消耗与总热量消耗均下降,但采取低脂饮食时下降更明显,差异有统计学意义。此外,采取低脂饮食时受试者的血清瘦素水平最高。上述结果提示,采取低脂饮食者比采取另2种饮食者更可能体重反弹(JAMA 2012;307:2627-34)。


不仅如此,低脂饮食对外周和肝脏胰岛素敏感性、血清HDL胆固醇、甘油三酯和纤溶酶原激活物抑制物-1的不利影响也最强。与此相反,极低碳水化合物饮食对代谢综合征成分和热量消耗的正面影响最强。


然而,极低碳水化合物饮食可导致更高的C反应蛋白与皮质醇分泌水平,而后两者是生理应激和慢性炎症的标志物。此外,“高皮质醇水平高还可能促进肥胖、胰岛素抵抗与心血管疾病”。


研究者认为:“上述结果提示,降低糖负荷而不是减少脂肪的膳食策略,可能更有利于维持减肥效果和预防心血管疾病。”


这项研究的主要限制性在于“难以将结果外推至更自然的情景中(采取自我选择的饮食)。特别是,很多人难以长期坚持极低碳水化合物饮食。”


Pennington生物医学研究中心 的George A. Bray博士在随刊述评中指出:“上述令人兴奋的结果凸显出了我们对膳食元素和热量消耗重要性认识不足的现状,尤其是在减肥后的重要性。”(JAMA 2012;307:2641-42)。


然而Bray博士强调,由于每种饮食只执行了1个月,所以很难解读研究结果。而且研究者是基于加速度计判断在体力活动方面无组间差异,“而这不是一个理想的指标”,实际上研究结果可能受到了运动差异的影响。


这项研究由美国国立糖尿病、消化与肾脏疾病研究所、美国国立研究资源中心和新平衡基金会的支持。无其他利益冲突披露。Bray博士报告称与雅培实验室、武田全球研究所、快验保、康宝莱和Global Direction in Medicine有关系,并因撰写《肥胖手册》而获得稿酬。


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MARY ANN MOON
Elsevier Global Medical News
Breaking News


Three different diets designed to maintain a recent weight loss were found to exert markedly different metabolic effects independently of their energy content in obese and overweight young adults, according to a report in the June 27 issue of JAMA.


“The results of our study challenge the notion that a calorie is a calorie from a metabolic perspective,” said Cara B. Ebbeling, Ph.D., of the New Balance Foundation Obesity Prevention Center, Children’s Hospital Boston, and her associates.


The researchers performed a controlled feeding study to compare the effects of three weight-loss-maintenance diets on energy expenditure, hormones, and components of the metabolic syndrome. Their first step was to screen 681 men and women aged 18-40 years with a BMI of 27 or higher for participation in the study. Of these, only 32 potential subjects (17 men and 15 women) met entry criteria and agreed to the rigorous dietary restrictions of the study. Of these 32 subjects, 21 completed the study and were included in the data analysis.


During the run-in phase of the study, subjects followed a standard low-calorie diet that restricted energy intake to achieve a 12.5% decrease in body weight. Detailed assessments also were done to establish each subject’s energy requirements for stabilizing their weight at this reduced level.


After the subjects achieved a 10%-15% weight reduction, they each consumed one of the three isocaloric diets for 4 weeks, then switched to another of the diets for another 4 weeks, then to the third diet for a final 4 weeks in a three-way crossover design.


The three diets were the following: a low-fat diet with a high glycemic load and 20% of energy from protein, which reflected conventional recommendations to reduce fat, increase whole grain products, and include a variety of vegetables and fruits; a low-glycemic-index diet with moderate glycemic load and and 20% of energy from protein, which replaced some grain products and starchy vegetables with other vegetables, legumes, and fruits; and a very-low-carbohydrate diet with a low glycemic load and 30% of energy from protein, which was modeled on the Atkins diet.


Body weight did not differ significantly among the three maintenance diets, nor did total physical activity or time spent performing moderate to vigorous-intensity activity. Subjects’ ratings of subjective hunger and well-being did not differ significantly among the diets, and blood pressure levels also did not differ.


Both resting energy expenditure and total energy expenditure decreased with all the diets, but the decrease was significantly greater with the low-fat diet. In addition, serum leptin levels were highest with the low-fat diet. These two findings suggest that people following the low-fat diet would be more likely to regain weight than those following the other diets, Dr. Ebbeling and her colleagues said (JAMA 2012;307:2627-34).


Moreover, the low-fat diet also had the most unfavorable effects on peripheral and hepatic insulin sensitivity, serum HDL cholesterol, triglycerides, and plasminogen activator inhibitor 1.


In contrast, the very-low-carbohydrate diet had the most favorable effects on these components of the metabolic syndrome and on energy expenditure.


The very-low-carbohydrate diet, however, produced higher C-reactive protein levels and higher cortisol excretion levels than the other diets, both of which signal physiological stress and chronic inflammation. In addition, “higher cortisol levels may promote adiposity, insulin resistance, and cardiovascular disease,” the investigators wrote.


“These findings suggest that a strategy to reduce glycemic load rather than dietary fat may be advantageous for weight-loss maintenance and CVD prevention,” they noted.


The chief limitation of this study is “the difficulty extrapolating findings from a feeding study to a more natural setting, in which individuals consume self-selected diets. In particular, the very-low-carbohydrate diet involved more severe carbohydrate restriction than would be feasible for many individuals over the long term,” Dr. Ebbeling and her associates said.


“These provocative results by Ebbeling et al. emphasize the current incomplete knowledge base regarding the importance of dietary macronutrients and energy expenditure, especially after weight loss,” Dr. George A. Bray wrote in an accompanying editorial (JAMA 2012;307:2641-42).


It is difficult, however, to interpret the study’s findings when each maintenance diet was only followed for 1 month. And the authors found no differences among the groups in physical activity based on accelerometry, which is “an imperfect measure,” so differences in exercise may well have influenced the results, noted DR. Bray of Pennington Biomedical Research Center in Baton Rouge, La.


This study was supported by the U.S National Institute of Diabetes and Digestive and Kidney Diseases, the U.S. National Center for Research Resources, and the New Balance Foundation. No other financial conflicts of interest were reported. Dr. Bray reported ties to Abbott Laboratories, Takeda Global Research Institute, Medifast, Herbalife, and Global Direction in Medicine. He also has received royalties for the “Handbook of Obesity.”


学科代码:内科学 心血管病学 内分泌学与糖尿病   关键词:维持减肥效果的饮食
来源: EGMN
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