改善健康也許很簡單:每天少吃300卡大綱
Cutting 300 Calories a Day Shows Health Benefits
改善健康也許很簡單：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.
科學家們早就知道一種相當可靠的方式，能夠延長齧齒類及其他實驗室動物的壽命：把他們攝入的卡路里數量減少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.
這種被稱爲卡路里限制的策略已被證實可延長各種生物的壽命，並降低它們患癌症及其他年齡相關疾病的機率。它是否能對人類起到同樣的作用尚無定論。但一項饒有趣味的新研究表明，長期限制青壯年人的卡路里攝入可對他們的健康產生影響。
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.
這項新研究由美國國家衛生研究院（National Institutes of Health，簡稱NIH）出資並發表在本月的《柳葉刀糖尿病與內分泌學》(Lancet Diabetes & Endocrinology)期刊上，其中研究人員對一羣年齡介乎21歲至50歲的143名健康男性和女性進行了觀察。他們按照指示，進行了爲期兩年的卡路里攝入限制。他們可以食用自己想要的食物，條件是減少攝入食物總量，目標是使他們攝入的熱量減少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.
很多人沒達到這一目標。平均而言，節食者得以將總熱量削減了約12%，大致相當於每天300卡路里，這是一個大貝果、幾塊巧克力曲奇或一小杯星巴克摩卡星冰樂的熱量。但這組人中，很多人的心血管和新陳代謝健康指標都得到了改善，儘管他們原本已在正常範圍內。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.
他們的體重和體脂均有下降。他們的膽固醇水平有所改善，血壓略有下降，血糖控制情況好轉，炎症發作也減少。與此同時，未實行卡路里限制的75名對照組健康人士的這些指標沒有改善。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.
卡路里限制組的受益部分源於他們的體重大幅降低，在研究進行的兩年期間平均減少了16磅。但他們代謝健康狀況的改善程度大於減重本身的預期，這表明熱量限制可能對身體的疾病通道有某種獨特的生物作用，該研究第一作者、杜克大學醫學和心臟病學教授威廉·克勞斯(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."
“有變化我們並不意外，”他說。“但變化的幅度着實驚人。在疾病人羣中，任何的五種藥物組合能無法產生這麼大的改善。”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.
熱量限制或許是改善健康和減輕體重的有用途徑，但尚不清楚這項新研究所揭示的變化最終能否轉化爲壽命延長和慢性病的減少，未參與該研究的哈佛大學陳曾熙公共衛生學院(Harvard T.H. Chan School of Public Health)營養學系主任胡炳長(Frank Hu)稱。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，參與者所經歷的適度改善必須長時間保持，方能產生長期的益處。但鑑於“我們生活在一個致胖環境中，有大量能量密集但缺乏營養的食物，它們廉價、容易獲得還很熱銷”，熱量限制對於大多數人是否實際，他表示質疑。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.
不過他也表示，一些人可能會發現熱量限制是可行的，如果他們把它和地中海飲食、間歇性禁食或減少碳水化合物攝入這類熱門飲食策略結合起來的話。
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.
這項新研究證實限制卡路里何其困難。研究參與者接受了密集的培訓項目，從中學習如何烹製低卡路里餐食，參加了小組討論並定期向營養專家諮詢。但他們仍然連25%的熱量削減目標的一半都達不到。而任何有過節食經驗的人都知道，長期保持減重效果是最難的。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.
但新研究在多個方面都有開創性。研究完全由NIH資助，耗資5500萬美元，全名爲“Calerie”——降低能量攝入長期效應綜合評估(Comprehensive Assessment of Long-term Effects of Reducing Intake of Energy)。這是以體重正常或輕微超重但不肥胖的青壯年爲對象，檢驗卡路里攝入限制影響的首例主要臨牀試驗。試驗旨在查看熱量限制能否影響健康老齡化進程和疾病狀況。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.
雖然他們設定的卡路里目標非常嚴格，但也給了受試者一些靈活性，讓他們可以吃自己想吃的食物。他們發現，研究對象的蛋白質攝入量並沒有改變，但他們攝入的脂肪和碳水化合物明顯減少。研究報告作者之一、塔夫茨大學USDA人類衰老營養研究中心(Tufts University U.S.D.A. Human Nutrition Research Center on Aging)資深科學家蘇珊·B·羅伯茨(Susan B. Roberts)說，受試者還攝入了維生素A、K和鎂等更多微量元素，表明水果和蔬菜的攝入量有了大幅增加。"They were eating more healthy foods," she said. "Things like nuts, whole grains, green vegetables and legumes."
“他們吃得更健康，”她說。“比如堅果、全穀物、綠色蔬菜和豆類之類東西。”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.
對許多人來說，節食可能是一種不愉快的經歷。但研究人員發現，對許多受試者來說，令他們驚訝的是，熱量限制不是無法忍受的。雖然退出節食組的人比對照組多，但總的來說，這項研究的受試者保留率很高。研究人員研究了生活質量的衡量標準，發現限制熱量攝入的那組人睡眠更好、精力更充沛、情緒也更好。羅伯茨說，與對照組相比，他們的飢餓感和對食物的渴望也沒有明顯增加。"There was nothing we measured that indicated that they weren't doing well," she said.
“我們沒有測量到任何表明他們情況不好的東西，”她說。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.
這項研究無法回答的一個問題是，熱量限制是否能像延長其他動物壽命一樣延長人類的壽命。要想測試這一點，研究人員只能讓人們保持這樣的飲食，並且繼續跟蹤他們幾十年。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.
但最終，熱量限制確實對糖尿病和心臟病的一系列風險因素產生了有益影響。這兩種疾病導致數以百萬計美國人的死亡和殘疾，隨着是年紀較長者。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.
杜克大學的克勞斯說，他希望在10年內再次對參與者進行研究，看看熱量限制實驗的好處是否能夠持續下去。這種現象被稱爲遺留效應，在高強度運動訓練和其他健康干預措施中都存在。但就目前而言，他說，該實驗對公衆的啓示是，從每天的飲食中減少300卡路里的熱量可以令人們獲益。"It's not that hard to achieve that amount of caloric restriction," he said. "That's essentially an after-dinner snack."
“達到這個熱量限制並不難，”他說。“基本上就是一頓餐後小吃的量。”
