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Cutting 300 Calories a Day Shows Health Benefits
改善健康也许很简单：每天少吃300卡
Scientists have long known a fairly reliable way to extend life span in rodents and other lab animals: Reduce the amount of calories they eat by 10 percent to 40 percent.
科学家们早就知道一种相当可靠的方式，能够延长啮齿类及其他实验室动物的寿命：把他们摄入的卡路里数量减少10%至40%。
This strategy, known as caloric restriction, has been shown to increase the life span of various organisms and reduce their rate of cancer and other age-related ailments. Whether it can do the same in people has been an open question. But an intriguing new study suggests that in young and middle-aged adults, chronically restricting calorie intake can have an impact on their health.
这种被称为卡路里限制的策略已被证实可延长各种生物的寿命，并降低它们患癌症及其他年龄相关疾病的几率。它是否能对人类起到同样的作用尚无定论。但一项饶有趣味的新研究表明，长期限制青壮年人的卡路里摄入可对他们的健康产生影响。
In the new study, which was funded by the National Institutes of Health and published this month in the Lancet Diabetes & Endocrinology, researchers looked at a group of 143 healthy men and women who ranged in age from 21 to 50. They were instructed to practice caloric restriction for two years. They could eat the foods they wanted so long as they cut back on the total amount of food they ate, with the aim of cutting the calories they consumed by 25 percent.
这项新研究由美国国家卫生研究院（National Institutes of Health，简称NIH）出资并发表在本月的《柳叶刀糖尿病与内分泌学》(Lancet Diabetes & Endocrinology)期刊上，其中研究人员对一群年龄介乎21岁至50岁的143名健康男性和女性进行了观察。他们按照指示，进行了为期两年的卡路里摄入限制。他们可以食用自己想要的食物，条件是减少摄入食物总量，目标是使他们摄入的热量减少25%。
Many did not achieve that goal. On average, the dieters managed to slash about 12 percent of their total calories, or roughly 300 calories a day, the amount in a large bagel, a few chocolate chip cookies or a small Starbucks Mocha Frappuccino. But the group saw many of their cardiovascular and metabolic health markers improve, even though they were already in the normal range.
很多人没达到这一目标。平均而言，节食者得以将总热量削减了约12%，大致相当于每天300卡路里，这是一个大贝果、几块巧克力曲奇或一小杯星巴克摩卡星冰乐的热量。但这组人中，很多人的心血管和新陈代谢健康指标都得到了改善，尽管他们原本已在正常范围内。
They lost weight and body fat. Their cholesterol levels improved, their blood pressure fell slightly, and they had better blood sugar control and less inflammation. At the same time, a control group of 75 healthy people who did not practice caloric restriction saw no improvements in any of these markers.
他们的体重和体脂均有下降。他们的胆固醇水平有所改善，血压略有下降，血糖控制情况好转，炎症发作也减少。与此同时，未实行卡路里限制的75名对照组健康人士的这些指标没有改善。
Some of the benefits in the calorie restricted group stemmed from the fact that they lost a large amount of weight, on average about 16 pounds over the two years of the study. But the extent to which their metabolic health got better was greater than would have been expected from weight loss alone, suggesting that caloric restriction might have some unique biological effects on disease pathways in the body, said William Kraus, the lead author of the study and a professor of medicine and cardiology at Duke University.
卡路里限制组的受益部分源于他们的体重大幅降低，在研究进行的两年期间平均减少了16磅。但他们代谢健康状况的改善程度大于减重本身的预期，这表明热量限制可能对身体的疾病通道有某种独特的生物作用，该研究第一作者、杜克大学医学和心脏病学教授威廉·克劳斯(William Kraus)表示。
"We weren't surprised that there were changes," he said. "But the magnitude was rather astounding. In a disease population, there aren't five drugs in combination that would cause this aggregate of an improvement."
“有变化我们并不意外，”他说。“但变化的幅度着实惊人。在疾病人群中，任何的五种药物组合能无法产生这么大的改善。”
Calorie restriction may be a useful tool for better health and weight loss, but it's unclear whether the changes in the new study will ultimately translate into longevity and reductions in chronic disease, said Frank Hu, the chairman of the nutrition department at the Harvard T.H. Chan School of Public Health, who was not involved in the research.
热量限制或许是改善健康和减轻体重的有用途径，但尚不清楚这项新研究所揭示的变化最终能否转化为寿命延长和慢性病的减少，未参与该研究的哈佛大学陈曾熙公共卫生学院(Harvard T.H. Chan School of Public Health)营养学系主任胡炳长(Frank Hu)称。
He said the modest improvements experienced by the participants would have to be sustained over time to produce long-term benefits. But he questioned whether caloric restriction would be practical for most people given that "we are living in an obesogenic environment with an abundance of energy-dense, nutrient-poor foods that are cheap, accessible and heavily marketed."
他表示，参与者所经历的适度改善必须长时间保持，方能产生长期的益处。但鉴于“我们生活在一个致胖环境中，有大量能量密集但缺乏营养的食物，它们廉价、容易获得还很热销”，热量限制对于大多数人是否实际，他表示质疑。
He added, however, that some people might find calorie restriction feasible if they combined it with other popular dietary strategies like the Mediterranean diet, intermittent fasting or reduced carbohydrate intake.
不过他也表示，一些人可能会发现热量限制是可行的，如果他们把它和地中海饮食、间歇性禁食或减少碳水化合物摄入这类热门饮食策略结合起来的话。
The new study provided evidence of just how difficult calorie restriction can be. The study participants went through an intensive training program where they learned to cook low-calorie meals, attended group sessions and had regular check-ins with nutrition experts. Still, they were not able to meet even half the goal of a 25 percent cut in calories. And as anyone who has dieted knows, keeping the weight off long-term can be the hardest part.
这项新研究证实限制卡路里何其困难。研究参与者接受了密集的培训项目，从中学习如何烹制低卡路里餐食，参加了小组讨论并定期向营养专家咨询。但他们仍然连25%的热量削减目标的一半都达不到。而任何有过节食经验的人都知道，长期保持减重效果是最难的。
Still, the new study was groundbreaking in several ways. Funded entirely by the N.I.H. at a cost of $55 million and called Calerie — for Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy — it was the first major clinical trial to examine the effects of caloric restriction in a group of middle-aged or younger adults who were either normal weight or just slightly overweight but not obese. The goal of the trial was to look at whether caloric restriction could influence healthy aging and disease.
但新研究在多个方面都有开创性。研究完全由NIH资助，耗资5500万美元，全名为“Calerie”——降低能量摄入长期效应综合评估(Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy)。这是以体重正常或轻微超重但不肥胖的青壮年为对象，检验卡路里摄入限制影响的首例主要临床试验。试验旨在查看热量限制能否影响健康老龄化进程和疾病状况。
While the calorie target they set was steep, they did give the subjects some flexibility, allowing them to eat the foods that they wanted. What they found was that the subjects did not change their protein intake, but they did eat significantly less fat and slightly fewer carbohydrates. They also consumed more micronutrients like vitamins A, K and magnesium, indicating a big increase in fruits and vegetables, said Susan B. Roberts, a co-author of the study and a senior scientist at the U.S.D.A. Human Nutrition Research Center on Aging at Tufts University.
虽然他们设定的卡路里目标非常严格，但也给了受试者一些灵活性，让他们可以吃自己想吃的食物。他们发现，研究对象的蛋白质摄入量并没有改变，但他们摄入的脂肪和碳水化合物明显减少。研究报告作者之一、塔夫茨大学USDA人类衰老营养研究中心(Tufts University U.S.D.A. Human Nutrition Research Center on Aging)资深科学家苏珊·B·罗伯茨(Susan B. Roberts)说，受试者还摄入了维生素A、K和镁等更多微量元素，表明水果和蔬菜的摄入量有了大幅增加。
"They were eating more healthy foods," she said. "Things like nuts, whole grains, green vegetables and legumes."
“他们吃得更健康，”她说。“比如坚果、全谷物、绿色蔬菜和豆类之类东西。”
For many people, dieting can be an unpleasant experience. But the researchers found that for many of the subjects, caloric restriction was surprisingly not unbearable. While more people dropped out of the diet group than the control group, the study overall had a high retention rate. The researchers looked at measures of quality of life and discovered that the calorie-restricted group reported better sleep, increased energy and improved mood. Compared to the control group, they did not have significant increases in hunger or food cravings either, Dr. Roberts said.
对许多人来说，节食可能是一种不愉快的经历。但研究人员发现，对许多受试者来说，令他们惊讶的是，热量限制不是无法忍受的。虽然退出节食组的人比对照组多，但总的来说，这项研究的受试者保留率很高。研究人员研究了生活质量的衡量标准，发现限制热量摄入的那组人睡眠更好、精力更充沛、情绪也更好。罗伯茨说，与对照组相比，他们的饥饿感和对食物的渴望也没有明显增加。
"There was nothing we measured that indicated that they weren't doing well," she said.
“我们没有测量到任何表明他们情况不好的东西，”她说。
One question the study could not answer was whether caloric restriction could extend life span in humans the way that it can in other animals. The researchers would have to keep people on the diet and follow them for many decades to test that.
这项研究无法回答的一个问题是，热量限制是否能像延长其他动物寿命一样延长人类的寿命。要想测试这一点，研究人员只能让人们保持这样的饮食，并且继续跟踪他们几十年。
But ultimately, caloric restriction did have a beneficial impact on a wide range of risk factors for diabetes and heart disease, two conditions that cause death and disability for millions of Americans, especially as they get older.
但最终，热量限制确实对糖尿病和心脏病的一系列风险因素产生了有益影响。这两种疾病导致数以百万计美国人的死亡和残疾，随着是年纪较长者。
Dr. Kraus at Duke said he hoped to study the participants again in 10 years to see if the benefits of the caloric restriction experiment persist, a phenomenon known as legacy effects, which can occur with intense exercise training and other health interventions. But for now, he said that one takeaway for the public is that people can benefit from shaving as little as 300 calories a day from their diets.
杜克大学的克劳斯说，他希望在10年内再次对参与者进行研究，看看热量限制实验的好处是否能够持续下去。这种现象被称为遗留效应，在高强度运动训练和其他健康干预措施中都存在。但就目前而言，他说，该实验对公众的启示是，从每天的饮食中减少300卡路里的热量可以令人们获益。
"It's not that hard to achieve that amount of caloric restriction," he said. "That's essentially an after-dinner snack."
“达到这个热量限制并不难，”他说。“基本上就是一顿餐后小吃的量。”
