加強運動也許并不能減肥

If you give a mouse a running wheel, it will run.

如果給小鼠一個轉(zhuǎn)輪，它就會跑起來。

But it may not burn many additional calories, because it will also start to move differently when it is not on the wheel, according to an interesting new study of the behaviors and metabolisms of exercising mice.

但它可能不會燃燒太多額外的熱量，一項有趣的新研究對鍛煉的小鼠的行為與新陳代謝進行了研究，發(fā)現(xiàn)不在轉(zhuǎn)輪上的時候，小鼠的行為也會開始改變。

The study, published in Diabetes, involved animals, but it could have cautionary implications for people who start exercising in the hopes of losing weight.

發(fā)表在《糖尿病》(Diabetes)上的這項研究是關于動物的，但對于抱著減肥的希望開始鍛煉的人，它可能也有警示意義。

In recent years, study after study examining exercise and weight loss among people and animals has concluded that, by itself, exercise is not an effective way to drop pounds.

近年來，一項又一項研究以人和動物的鍛煉與減肥為內(nèi)容，它們斷定運動本身并不是一種有效的減肥方式。

In most of these experiments, the participants lost far less weight than would have been expected, mathematically, given how many additional calories they were burning with their workouts.

在其中大部分實驗中，考慮到鍛煉中燃燒的大量額外熱量，參與者減掉的體重從數(shù)字上來說遠低于預期。

Scientists involved in this research have suspected and sometimes shown that exercisers, whatever their species, tend to become hungrier and consume more calories after physical activity. They also may grow more sedentary outside of exercise sessions. Together or separately, these changes could compensate for the extra energy used during exercise, meaning that, over all, energy expenditure doesn’t change and a person’s or rodent’s weight remains stubbornly the same.

參與這些研究的科學家懷疑——有時也會證明——無論是人還是動物，鍛煉之后往往會變得更加饑餓，從而攝入更多熱量。在鍛煉之外的時間里，他們可能還會變得更喜歡久坐。這些變化單獨或加起來都可能彌補鍛煉期間消耗的額外熱量。這意味著總的來說，能量消耗沒有變，人或嚙齒類動物的體重保持不變。

Proving that possibility has been daunting, though, in part because it is difficult to quantify every physical movement someone or something makes, and how their movements do or do not change after exercise. Mice, for instance, skitter, dart, freeze, groom, eat, roam, defecate and otherwise flit about in frequent fits and starts.

但是要證明這種可能性卻令人生畏。這在一定程度上是因為，人或動物的每一個動作、以及這些動作在鍛煉后的變化情況是難以量化的。比如，小鼠會躥跳、猛沖、發(fā)呆、梳毛、進食、閑逛、排便或斷斷續(xù)續(xù)地四處走動。

But recently, animal researchers hit upon the idea of using infrared light beams to track how animals move at any given moment in their cages. Sophisticated software then can use that information to map daily patterns of physical activity, showing, second-by-second, when, where and for how long an animal roams, sits, runs or otherwise spends its time.

但最近，以動物為對象的研究人員想到了一個辦法，用紅外線光束追蹤籠子里的動物在任意時刻的活動情況。然后，復雜的軟件可利用這些信息繪制出一天的身體活動模式，一秒一秒地顯示一只動物什么時候，在哪里逛、坐、跑了多久，或用其他方式度過了多長時間。

Intrigued, scientists at Vanderbilt University and other institutions thought that this technology would be ideal for tracking mice before and after they started exercising, especially if the technology were used in specialized metabolic-chamber cages that can quantify how much energy an inhabitant is expending throughout the day.

范德比爾特大學(Vanderbilt University)等機構(gòu)的科學家們對此很感興趣，他們認為，這項技術(shù)非常適合對小鼠鍛煉前后的情況進行跟蹤，尤其是用在專門的代謝室籠子里時——這種籠子可以量化棲息其中的一只動物一天內(nèi)消耗的能量。

So the scientists fitted out cages, added locked running wheels, and let young, healthy, normal-weight, male mice loose in them to roam and explore for four days, providing the researchers with baseline data about each mouse’s metabolism and natural peripatetic-ness.

所以，科學家們安好籠子，加裝了鎖住的跑步輪，讓年輕、健康、正常體重的雄性小鼠在籠子里自由漫步探索四天，為研究人員提供每只小鼠的新陳代謝和自然漫步的基礎數(shù)據(jù)。

The wheels then were unlocked and for nine days, the mice could run at will, while also eating and moving around off the wheels as much as they chose.

然后，這些輪子被解開了9天，小鼠可以在輪子上自由玩耍，也可以隨心所欲地吃東西，在輪子周圍活動。

The mice, which seem to enjoy running, hopped readily on the wheels and ran, off and on, for hours.

小鼠們似乎很喜歡在輪子上跑跳，或者從輪子上跳上跳下，持續(xù)數(shù)小時。

They showed a subsequent spike in their daily energy expenditure, according to the metabolic measures, which makes sense, since they had added exercise to their lives.

根據(jù)新陳代謝數(shù)據(jù)，它們的日常能量消耗隨之激增，這是合理的，因為它們的鍛煉量增加了。

But they did not change their eating habits. Although they were burning more calories, they did not gorge on more chow.

但它們的飲食習慣并沒有改變。它們雖然燃燒了更多的熱量，卻沒有吃掉更多的食物。

They did, however, alter how they moved. Almost immediately after they started using the wheels, they stopped roaming around their cages as they had before the wheels were unlocked.

不過，它們的活動方式的確改變了。幾乎從它們在輪子上跑步開始，它們就不再像輪子被鎖著時那樣在籠子里漫步了。

In particular, they stopped engaging in the kind of lengthy meanders that had been common before they began to run. Instead, they now usually jogged on their wheels for a few minutes, hopped off, rested or roamed in short spurts, and then climbed back on the wheels, ran, rested, briefly roamed, and repeated.

尤其是，它們停止了跑步前常見的漫長的散步活動。相反，它們現(xiàn)在通常在輪子上慢跑幾分鐘，跳下來，休息或者短時間散步一會兒，然后爬回輪子，跑，休息，短時散步，如此循環(huán)。

These changes in how they spent their time neatly managed to almost counteract the extra calorie costs from running, says Daniel Lark, a research fellow in molecular physiology at the Vanderbilt University School of Medicine, who led the new study.

這項新研究的負責人、范德比爾特大學醫(yī)學院的分子生理學研究員丹尼爾·拉克(Daniel Lark)表示，它們在時間安排上的改變幾乎抵消了跑步帶來的額外熱量消耗。

In general, the running mice showed a slightly negative energy balance, meaning that they were burning a few more calories over the course of the day than they were taking in by chowing down.

總的來說，跑步的小鼠表現(xiàn)出輕微的能量負平衡，也就是說，它們一天中燃燒的熱量比它們通過進食攝入的能量要多一點。

But that caloric deficit would have been about 45 percent greater, the metabolic calculations showed, if they had not also begun moving around their cages less.

但新陳代謝數(shù)據(jù)顯示，如果它們沒有減少在籠中的散步，那么，熱量赤字會增加約45%。

What prompted the running mice to roam less is still uncertain.

促使跑步的小鼠減少散步的原因尚不確定。

“But it does not seem to have been fatigue or lack of time,” Dr. Lark says.

“它們似乎并沒有表現(xiàn)出疲勞，也不是沒有時間，”拉克博士說。

Wheel running is not arduous for mice, he points out, and did not fill their waking hours.

他指出，對小鼠來說，在輪子上跑并不費力，也沒有占滿它們醒著的所有時間。

Instead, he says, it is likely that the animals’ bodies and brains sensed the beginnings of an energy deficit when the mice began to run and sent out biological signals that somehow advised the animals to slow down, conserve energy, maintain homeostasis and not drop weight.

他表示，小鼠的身體和大腦很可能意識到，開始跑步后會出現(xiàn)能量赤字，所以發(fā)出了生物信號，通過某種方式建議動物放慢速度，保存能量，保持內(nèi)環(huán)境平衡，不要導致體重下降。

He and his colleagues would like, in future experiments, to explore how, physiologically, the rodents’ bodies sensed the changes in their energy balance and at what point they might begin to eat more. They also would like to study female, older and obese animals.

他和同事們想在將來的實驗中探索嚙齒類動物的身體是如何從生理上感知到能量平衡變化，以及從何時起開始吃得更多。他們也想研究雌性、年老和肥胖的動物。

Mice will never be people, of course, so we cannot say whether the results of this and any follow-up experiments would directly apply to us, Dr. Lark says.

拉克博士表示，當然，小鼠跟人類永遠不一樣，所以我們無法確定這項試驗和后續(xù)試驗的結(jié)果是否可以直接適用于人類。

But the results do intimate that if we hope to exercise off excess pounds, we watch what we eat and try not to move less while we work out more.

但這些研究結(jié)果表明，如果我們希望通過運動減掉多余的體重，就應該關注自己的飲食，而且不要在增加鍛煉的同時減少其他身體活動。