纽约时报：别指望仅靠锻炼身体来减肥（双语）

Your Workout Burns Fewer Calories Than You Think

你锻炼身体消耗的卡路里没你想象的多

Our bodies compensate for at least a quarter of the calories we expend during exercise, undermining our best efforts to lose weight by working out.

我们的身体至少自动补偿了我们在运动中消耗的四分之一的卡路里，破坏了我们想通过运动减肥的最佳努力。

By Gretchen Reynolds, The New York Times, Sept. 22, 2021

作者：格雷琴·雷诺兹，纽约时报，2021年9月22日

For every 100 calories we might expect to burn as a result of working out, most of us will actually net fewer than 72 calories burned, according to an eye-opening new study of how physical activity affects our metabolisms.

根据一项影响我们新陈代谢的研究显示，我们预计因锻炼身体燃烧掉的每100卡路里中，我们中的大多数人实际燃烧的热量将少于72卡路里。

The study finds that our bodies tend to automatically compensate for at least a quarter of the calories we expend during exercise, undermining our best efforts to drop pounds by working out. The results also show that carrying extra pounds unfortunately compounds calorie compensation, making weight loss through exercise even more elusive for those who are already overweight.

研究发现，我们的身体倾向于自动补偿我们在运动中消耗的至少四分之一的卡路里，这破坏了我们通过运动减肥的最佳努力。研究结果还表明，不幸的是，如果身体超重还会增加这一热量补偿，这使得那些已经超重的人更难通过锻炼减肥。

But the study suggests, too, that calorie compensation varies from person to person, and that learning how your metabolism responds to workouts may be key to optimizing exercise for weight control.

但研究也表明，热量补偿因人而异，了解你的新陈代谢对锻炼的反应可能是优化锻炼以控制体重的关键。

In theory — or in a kindlier, alternative universe — exercise would aid substantially in weight loss. When we move, our muscles contract, requiring more fuel than at rest, while other organs and biological systems likewise expend extra energy. Thanks to past laboratory studies, we know approximately how much energy these processes demand. Walking a mile, for instance, burns approximately 100 calories, depending on someone’s body size and walking speed.

从理论上讲（或者在一个更仁慈的、有替代选择的世界里）运动将大大有助于减肥。当我们运动时，我们的肌肉收缩，需要比休息时更多的能量，而其他器官和生物系统也同样消耗额外的能量。由于过去的实验室研究，我们大致知道这些过程需要多少能量。例如，步行一英里可以消耗大约100卡路里的热量，这取决于一个人的体型和行走速度。

Until recently, most people, including exercise scientists, assumed that this process would be additive — that is, stroll a single mile, burn 100 calories. Stroll two, burn 200, and so on, in logical, mathematical fashion. If we do not then replace those calories with extra food, we should wind up burning more calories than we consume that day and start dropping pounds.

直到最近之前，包括运动科学家在内的大多数人都认为这一过程是增加性的——也就是说，散步一英里，燃烧100卡路里。以逻辑和数学的方式，漫步两次，燃烧200次，等等。如果我们不用额外的食物来代替这些卡路里，我们燃烧的卡路里会比当天消耗的更多，体重也会开始下降。

But that rational outcome rarely happens. In study after study, most people who begin a new exercise program lose less weight than would be expected based on the number of calories they burn during their workouts, even if they strictly monitor their diets.

但这种理性的结果很少发生。在一项又一项的研究中，大多数开始新的锻炼计划的人，即使他们严格监控自己的饮食，根据他们在锻炼过程中燃烧的卡路里数量，减少的体重也比预期的要少。

So, some scientists began speculating that energy expenditure might be less elastic than we had thought. In other words, it might have limits. That possibility gained traction in 2012, with the publication of an influential study of African hunter-gatherers. It showed that, although the tribespeople regularly walked or jogged for hours, they burned about the same number of total daily calories as relatively sedentary Western men and women. Somehow, the study’s authors realized, the active tribespeople’s bodies were compensating, dialing back overall calorie burning, so that they avoided starvation as they stalked their food.

因此，一些科学家开始推测能量消耗可能没有我们想象的那么有弹性。换句话说，它可能有局限性。这种可能性在2012年随着一份对非洲狩猎采集者有影响的研究报告发行得到了广泛关注。该研究表明，尽管非洲等采猎部落居民经常步行或慢跑数小时，但他们每天消耗的总热量和相对久坐不动的西方男性和女性相当。该研究的作者们意识到，不知何故，活跃部落的人们的身体在进行补偿，将总的热量燃烧拨回，这样他们就避免了在跟踪食物时挨饿。

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Other small studies since have reinforced the finding that more activity does not necessarily result in greater daily calorie expenditure. But few large-scale experiments have tried to pin down just how much our bodies compensate for the calories burned while moving, since measuring metabolic activity in people is complex and expensive.

其他一些小型研究进一步证实了这一发现多运动并不一定会导致更大的每日热量消耗。但很少有大型实验试图确定我们的身体在运动时对燃烧的卡路里的补偿程度，因为测量人体的代谢活动既复杂又昂贵。

As part of an ambitious new scientific initiative, however, dozens of researchers recently pooled their metabolic data from multiple studies involving thousands of men and women. These studies involved drinking doubly labeled water, the gold standard in metabolic research. It contains isotopes that allow researchers precisely to track how many calories someone burns throughout the day.

然而，作为一项雄心勃勃的新科学计划的一部分，数十名研究人员最近汇集了来自数千名男性和女性的多项研究的代谢数据。这些研究包括饮用双标签水，这是代谢研究的金标准。它含有同位素，使研究人员能够精确地追踪一个人一天中燃烧了多少卡路里。

For the new study, which was published in August in Current Biology, some of the scientists involved in the initiative set out to see what happens to our metabolisms when we move. They pulled data for 1,754 adults that included their doubly labeled water results, as well as measures of their body compositions and basal energy expenditure, which is how many calories they burn simply by being alive, even if they otherwise are inactive. Subtracting basal numbers from total energy expenditure gave the researchers an approximation of people’s energy expenditure from exercise and other movement, such as standing, walking and general fidgeting.

8月份发表在《当代生物学》上的这项新研究中，参与这项活动的一些科学家着手研究我们移动时的代谢情况。他们收集了1754名成年人的数据，其中包括他们的双标签饮水结果，以及他们的身体成分和基本能量消耗的测量结果，即他们仅仅活着就燃烧了多少卡路里，即使他们没有活动。从总能量消耗中减去基本数字，研究人员得出了人们通过锻炼和其他运动（如站立、行走和一般坐立不安）所消耗能量的近似值。

Then, using statistical models, the researchers could tally whether calories burned during activity increased people’s daily energy expenditure as expected — that is, whether people burn commensurately more total daily calories when they move more. But, the researchers found, they did not tend to burn more calories. In fact, most people seemed to be burning only about 72 percent as many additional calories, on average, as would be expected, given their activity levels.

然后，利用统计模型，研究人员可以统计出在活动中燃烧的卡路里是否如预期的那样增加了人们的日常能量消耗——也就是说，当人们运动得更多时，是否相应地燃烧了更多的每日总卡路里。但是，研究人员发现，结果是人们并不倾向于燃烧更多的卡路里。事实上，考虑到他们的活动水平，大多数人似乎平均只燃烧了72%的额外运动消耗卡路里。

“People appear to be energy compensating for additional calories burned through activity by at least a quarter,” said Lewis Halsey, a professor of life and health sciences at the University of Roehampton in London and one of the lead authors of the new study.

伦敦州罗汉普顿大学生命与健康科学教授Lewis Halsey和这项新研究的主要作者之一说：“人们对能量消耗的能量补偿似乎至少是四分之一。”

Unexpectedly, the researchers also found that energy compensation levels increased among people with relatively high levels of body fat. They tended to compensate for 50 percent or more of the calories they burned by being active.

出乎意料的是，研究人员还发现，体内脂肪含量相对较高的人的能量补偿水平还增加了。他们通过积极运动后身体往往能补偿出他们燃烧的50%或更多的卡路里。

It is important to point out that the study did not look at people’s food intake. It concentrated solely on energy outlay and how our bodies seem able to offset some of the calories burned during exercise by reducing biological activity elsewhere in the body. Just how we unconsciously orchestrate this feat, though, and which internal systems could be most affected remain unclear, Dr. Halsey said. He and his colleagues speculate that immune system operations, which require considerable energy, may get dialed down somewhat. Or we could unknowingly fidget less or otherwise grow more sedentary, over all, on days we exercise. Perhaps, too, some of the inner workings of our cells may slow, reducing our bodies’ overall energy expenditure.

需要指出的是，这项研究并没有关注人们的食物摄入量。它只关注能量支出以及我们的身体如何通过减少身体其他部位的生物活动来抵消运动中燃烧的部分卡路里。哈尔西博士说，我们是如何无意识地策划这一壮举的，以及哪些内部系统可能受到的影响最大，目前尚不清楚。他和他的同事推测，需要消耗相当大能量的人体免疫系统操作可能会有所减弱。或者，在我们锻炼的日子里，我们会不知不觉地少那么一点坐立不安，或者变得更久坐不动。也许，我们细胞的某些内部运作也会减慢，从而减少我们身体的整体能量消耗。

But the new science of exercise and calorie compensation is not completely discouraging. Even people whose bodies compensate for 50 percent or more of the calories they expend during physical activity will burn more calories per day than if they remain still, Dr. Halsey pointed out. A more intractable problem with using exercise for weight loss, he continued, is that exercise realistically burns few calories, period. To drop pounds, we also will have to eat less.

但是关于运动和热量补偿的新科学并没有完全令人沮丧。哈尔西博士指出，即使是身体补偿了他们在体育活动中消耗的50%或更多热量的人，每天也会比保持静止燃烧更多的热量。他继续说，利用运动减肥还有一个更棘手的问题，那就是运动实际上消耗的卡路里很少。为了减肥，我们还必须少吃。

“Half a cookie or half a can of cola” after a half-hour walk, and you will have taken in more calories than you burned, he said, however much or little you compensate.

他说，步行半小时后“吃半块饼干或半罐可乐”，你摄入的卡路里将超过你燃烧的卡路里，不管你补偿的能量是多是少。