爲什麼運動不能幫所有人甩掉脂肪大綱

Exercise has innumerable health benefits, but losing weight may not be among them. A provocative new study shows that a substantial number of people who take up an exercise regimen wind up heavier afterward than they were at the start, with the weight gain due mostly to extra fat, not muscle.

運動對健康有數不清的益處，但減肥可能並非其中之一。一項富有挑戰意味的新研究表明，很多人在開始執行體育鍛煉計劃後體重反而有所增加，更糟糕的是，增加的這部分大多是多餘的脂肪而不是肌肉。

But the study also finds, for the first time, that one simple strategy may improve people’s odds of actually dropping pounds with exercise.

但也正是這同一項研究首次發現了一種可以切實增加人們運動減肥機率的簡單策略。

As we all know, the fundamentals of weight loss should be simple. Burn more calories on any given day than you consume and, over time, you will lose weight. Theoretically, we can achieve that desirable condition by reducing the number of calories that we take in through dieting or by increasing the number of calories that we incinerate through exercise.

我們都知道，減肥的基本原理非常簡單。只要你每天消耗的熱量多於攝入量，隨着時間的推移，你就會越來越瘦。從理論上說，通過節食減少熱量攝入或通過運動增加熱量消耗都能達到上述理想狀況。

But in reality, most people do not achieve or sustain weight loss, no matter what method they try.

但在現實中，大多數人試遍了所有方法，還是沒能達到或維持所希望的減肥效果。

Exercise is particularly problematic in this regard. A recent review of studies related to exercise and weight control found that in most of the studies, people lost barely a third as many pounds as would have been expected, given how many calories they were burning during workouts. Many studies also report enormous variations in how people’s waistlines respond to the same exercise program, with some people dropping pounds and others gaining fat.

在這方面，運動的問題尤其大。近期的一項關於運動和體重控制研究的綜述發現，在大多數的研究中，人們在運動後的體重減輕量，只有按照鍛鍊消耗的卡路里數換算出來的預期減重量的三分之一。許多研究還報告，即使執行相同的鍛鍊計劃，不同的人的腰圍變化之間也存在巨大差異，一部分人的體重減輕了，另一部分人反倒更胖了。

Scientists have had little understanding, however, of why exercise helps some people but not others to shed pounds or whether there might be early indications of how people will respond to an exercise routine.

但是，對於爲什麼運動能夠幫助某些人甩掉贅肉卻對另一些人毫無用處，科學家們仍然沒什麼頭緒，此外，他們也不清楚是否有什麼早期指徵可以預測，有規律的鍛鍊對具體的某個人的效果如何。

So for the new study, which was published last month in The Journal of Strength and Conditioning Research, scientists at Arizona State University in Phoenix recruited 81 healthy but sedentary adult women. All of the women were overweight, based on their body mass index, but some were significantly heavier than others. None had exercised regularly in the past year.

上個月，《力量與訓練研究雜誌》(The Journal of Strength and Conditioning Research)上發表了一項新研究。在這項研究中，位於菲尼克斯的亞利桑那州立大學(Arizona State University)的科學家們招募了81名習慣久坐不動的健康成年女性。根據身體質量指數(B.M.I.)來判斷，她們全都超重，但其中一部分人超重更爲顯著。在過去一年裏，她們均未進行過有規律的鍛鍊。

The women were told that they would be joining a fitness study and would exercise in order to improve their aerobic endurance. The scientists asked the women not to change their eating habits in any way.

科學家們告訴這些受試女性，她們將參加一項以增強有氧耐力爲目標的健身研究，並要求她們不要對原來的飲食習慣作出任何改變。

Each of the volunteers visited the physiology lab at the start of the study and the scientists determined their weight, B.M.I., percentage of body fat, current endurance level, and others measures of health and fitness.

在研究開始時，每名志願者都來到生理實驗室，接受了體重、B.M.I.、體脂百分比、當前耐力水平等多種健康和健身指標的測定。

Then each woman began a supervised exercise program designed to be vigorous but manageable by most people, said Glenn Gaesser, a professor of nutrition and health promotion at Arizona State and senior author of the study. The women walked on treadmills at the laboratory three times per week for 30 minutes at a pace that represented about 80 percent of their maximum endurance.

其後，她們開始在監督下執行鍛鍊計劃，而且，據該研究的資深作者、亞利桑那州立大學的營養和健康促進學教授格倫·蓋瑟(Glenn Gaesser)稱，該計劃設計的運動強度很大，但還在大多數人可以接受的範圍內。受試女性每週要在實驗室的跑步機上完成三次走步鍛鍊，每次30分鐘，且節奏須保持在她們最大耐力80%的水平。

They continued the program for 12 weeks, with the scientists repeating the original fitness and other tests every month during that time.

整個鍛鍊計劃持續了12周，在此期間，科學家們每月都對受試者們進行一次與開始時一樣的健身指標複查。

At the end of 12 weeks, the women were all significantly more aerobically fit than they had been at the start. But many were fatter. Almost 70 percent of the women had added at least some fat mass during the program, and several had gained as much as 10 pounds, most of which was from fat, not added muscle.

在第12周結束時，這些女性的有氧能力均比開始時顯著改善，但其中有不少人更胖了。在整個研究過程中，有近70%的女性體脂肪量增加，有幾個人體重增量達4.5千克，且其中大部分是脂肪而非肌肉的增加。

A few of the women, though, had lost that much fat or more, and quite a few had remained at the same weight as at the start of the regimen.

不過，仍有少數女性減掉了等量甚至更多的脂肪，還有相當一部分女性的體重與研究開始時持平。

At this point, the researchers returned to the data from the first day of the study, to determine whether any obvious differences existed between the women who subsequently gained or lost weight. “Some past studies of dieting had indicated that women who weigh more at the beginning” of a weight-loss program “tend to lose more weight during the program,” Dr. Gaesser said.

這時，研究人員回過頭來審視研究第一天時獲得的數據，想要確定後來體重增加或減少的女性之間是否存在任何明顯的差異。蓋瑟博士說：“既往進行的一些有關節食的研究表明”，在減肥計劃“開始時體重較重的女性更容易在鍛鍊期間減肥”。

But the researchers found no correlation in this case between a woman’s weight at the start and end of the study. In fact, the scientists found no connection between any of the original parameters of health and fitness and the women’s responses to the exercise program.

但在該研究中，研究人員們發現受試女性研究開始時與結束時的體重間並沒有這種相關性。事實上，科學家們發現，這些女性在研究開始時的任何一項健康和健身參數與鍛鍊計劃對她們的效果都沒有關聯。

But looking deeper into their data, they discovered one interesting indicator: Those women who were losing weight after four weeks of exercise tended to continue to lose weight, while the others did not.

但隨着更加深入地研究數據，他們發現了一個有趣的指徵：經過四周的鍛鍊體重有所減輕的女性在後續的鍛鍊中往往更容易繼續減肥，而在其他人身上則並非如此。

“What that means in practical terms is that someone who wants to lose weight with exercise” should step on the bathroom scale after a month, Dr. Gaesser said. If at that point your weight remains stubbornly unchanged or has increased, “look closely at your diet and other activities,” he said.

“其實際指導意義就是，如果你想要依靠運動減肥，”就應該在鍛鍊一個月後去浴室裏稱一稱體重，”蓋瑟博士說。要是此時你的體重還是不見減輕或者反而更重了，“你就得好好注意下你的飲食和其他活動了。”

While this study didn’t track the women’s eating and movement habits away from the lab, it is likely that those who gained weight began eating more and moving less when they weren’t on the treadmills, “probably without meaning to,” Dr. Gaesser said.

這項研究並沒有對受試者們的飲食和實驗室之外的運動習慣進行追蹤，但蓋瑟博士認爲，那些在鍛鍊後體重增加的女性很可能是食量也隨之增加了，而且在跑步機鍛鍊以外的時間裏，她們的運動量更少了，“雖然這應該也不是存心的。”

Of course, the study was fairly short-term. It also did not involve men, although some past studies indicate that men, like women, frequently add fat mass after starting to exercise.

當然，這項研究的時間相當短，而且也沒有涉及到男性，不過此前有一些研究表明，男性和女性一樣經常出現在運動後體脂肪量反而增加的情況。

Still, the results, while sobering in some respects, also provide encouragement. By deploying a bathroom scale and discipline, along with exercise, you may well lose weight, Dr. Gaesser said.

儘管在某些方面，這些研究結果讓人覺得減肥大計形勢嚴峻，但它們也爲人們指明瞭希望的方向。蓋瑟博士表示，鍛鍊身體，嚴格自律，加上一隻放在浴室裏的體重計，你完全可能實現減肥。

Even more important, the women in the study were much fitter after four months of exercise, and Dr. Gaesser said “fitness matters far more for health than how much you weigh.”

更重要的是，在四個月的鍛鍊後，參與研究的這些女性的體質都大大改善了。蓋瑟博士說：“健身的意義更多地在於讓你更健康，而不是單純地要改變體重的那幾個數字。”