JAMA：体重减轻之后三种常见饮食对能量开支影响的比较研究

芝加哥–据6月27日刊《美国医学会杂志》JAMA上的一项初步的研究披露，在对3类常被食用饮食的能量开支及代谢综合征的成分所做的一项检查中，就静息能量开支及总能量开支的降低而言，低脂饮食最大，低血糖生成指数饮食居中，而极低碳水化合物饮食则最少，这提示与其它饮食相比，低脂饮食可能会有体重重新增加的风险。

根据文章的背景资料：“许多人可以在几个月中减轻体重，但大多数人会在长时间中很难维持有临床意义的体重减轻。根据国家卫生和营养检测调查（1999-2006）的数据，超重和肥胖的成年人中只有六分之一的人报告说他们维持至少10%的体重减轻达1年的时间。”长期后果不佳的一个解释是体重减轻引发了生物学上的适应——特别是能量支出的下降及饥饿的增加——这会促进体重的增加。据文章的作者披露，在维持体重减轻时的饮食组成对能量支出的影响还没有被研究过。

波士顿儿童医院的Cara B. Ebbeling， Ph.D.及其同事开展了一项研究，旨在评估3种维持体重减轻的饮食对能量支出、激素及代谢综合症的成分的影响。这项在2006年6月至2010年6月间开展的研究包括了21名超重和肥胖的青壮年。在进食一种补加饮食的同时取得10-15%的体重减轻之后，实验参与者以随机顺序进食一种等热卡低脂饮食（60%的能量来自碳水化合物，20%来自脂肪，20%来自蛋白质；高血糖生成负荷）、低血糖生产指数饮食（40%的能量来自碳水化合物，40%来自脂肪，20%来自蛋白质；中度血糖生成负荷）及极低碳水化合物饮食（10%的能量来自碳水化合物，60%来自脂肪，30%来自蛋白质；低血糖生成负荷），每种饮食进食时间为4周。检测的初级结果为静息能量支出（REE），次级结果有总体能量开支（TEE）、激素水平及代谢综合症的成分。

研究人员发现，在维持体重减轻时的能量开支在3种饮食中有着显著的差别。从体重减轻前水平的REE的降低——由禁食状态下的间接测热法来检测——幅度最大的是低脂饮食（相对于基线的平均值为-205 kcal/d），幅度居中的是低血糖生成指数饮食（-166 kcal/d），幅度最小的是极低碳水化合物饮食（-138 kcal/d）。TEE的下降也因饮食而有显著的差异（对低脂饮食来说平均为-423 kcal/d；对低血糖生成指数饮食来说平均为-297 kcal/d ；对极低碳水化合物饮食来说平均为-97 kcal/d）。

研究人员写道：“我们的研究结果挑战了热卡是从代谢角度来看的热卡的概念。TEE在这两种饮食[极低碳水化合物饮食vs.低脂饮食] 间相差了约300 kcal/d，这一效应相当于1小时的中等强度身体运动通常所消耗的能量。”

doi:10.1001/jama.2012.6607
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Effects of Dietary Composition on Energy Expenditure During Weight-Loss Maintenance

Cara B. Ebbeling, PhD; Janis F. Swain, MS, RD; Henry A. Feldman, PhD; William W. Wong, PhD; David L. Hachey, PhD; Erica Garcia-Lago, BA; David S. Ludwig, MD, PhD

Context Reduced energy expenditure following weight loss is thought to contribute to weight gain. However, the effect of dietary composition on energy expenditure during weight-loss maintenance has not been studied. Objective To examine the effects of 3 diets differing widely in macronutrient composition and glycemic load on energy expenditure following weight loss. Design, Setting, and Participants A controlled 3-way crossover design involving 21 overweight and obese young adults conducted at Children's Hospital Boston and Brigham and Women's Hospital, Boston, Massachusetts, between June 16, 2006, and June 21, 2010, with recruitment by newspaper advertisements and postings. Intervention After achieving 10% to 15% weight loss while consuming a run-in diet, participants consumed an isocaloric low-fat diet (60% of energy from carbohydrate, 20% from fat, 20% from protein; high glycemic load), low–glycemic index diet (40% from carbohydrate, 40% from fat, and 20% from protein; moderate glycemic load), and very low-carbohydrate diet (10% from carbohydrate, 60% from fat, and 30% from protein; low glycemic load) in random order, each for 4 weeks. Main Outcome Measures Primary outcome was resting energy expenditure (REE), with secondary outcomes of total energy expenditure (TEE), hormone levels, and metabolic syndrome components. Results Compared with the pre–weight-loss baseline, the decrease in REE was greatest with the low-fat diet (mean [95% CI], –205 [–265 to –144] kcal/d), intermediate with the low–glycemic index diet (–166 [–227 to –106] kcal/d), and least with the very low-carbohydrate diet (−138 [–198 to –77] kcal/d; overall P = .03; P for trend by glycemic load = .009). The decrease in TEE showed a similar pattern (mean [95% CI], −423 [–606 to –239] kcal/d; −297 [–479 to –115] kcal/d; and −97 [–281 to 86] kcal/d, respectively; overall P = .003; P for trend by glycemic load < .001). Hormone levels and metabolic syndrome components also varied during weight maintenance by diet (leptin, P < .001; 24-hour urinary cortisol, P = .005; indexes of peripheral [P = .02] and hepatic [P = .03] insulin sensitivity; high-density lipoprotein [HDL] cholesterol, P < .001; non-HDL cholesterol, P < .001; triglycerides, P < .001; plasminogen activator inhibitor 1, P for trend = .04; and C-reactive protein, P for trend = .05), but no consistent favorable pattern emerged. Conclusion Among overweight and obese young adults compared with pre–weight-loss energy expenditure, isocaloric feeding following 10% to 15% weight loss resulted in decreases in REE and TEE that were greatest with the low-fat diet, intermediate with the low–glycemic index diet, and least with the very low-carbohydrate diet. Trial Registration clinicaltrials.gov Identifier: NCT00315354