经济学人下载:肥胖 一个普遍的问题

Science and technology
科学技术

Obesity
肥胖

A wide spread problem
一个普遍的问题

The difficulty of losing weight is captured in a new model
新模式解读减肥难题

THE answer to obesity is obvious: eat less and exercise more.
减肥的办法很明显：少吃，多运动。

However, years of exhortation have failed to persuade most of those affected actually to do this.
年的忠告并没有说服大多数肥胖之人践行这一点。

In particular, it is much harder to shift surplus lard once it has accumulated than it is to avoid putting it on in the first place.
尤其是与避免累积脂肪相比，转化多余的累积脂肪要困难得多。

Oddly, though, a convenient mathematical model describing this fact has yet to be widely adopted.
不过，奇怪的是讲述这个事实的一个简易数学模式却没有被普通采用。

But a paper in this week's Lancet, by Kevin Hall of America's National Institutes of Health and his colleagues, aims to change that.

然而，多但是美国国家卫生研究所的凯文·霍尔及其同事在本周《柳叶刀》上发布的一篇论文旨在改变这种情况。

The conventional rule for slimming, espoused by both the NIH and Britain's National Health Service, has the benefit of simplicity:
美国国家卫生研究所和英国国家卫生服务共同支持的传统瘦身法具有简单的优势：

cut 500 calories each day and lose half a kilo a week.
每天减少500卡路里，每周可减少一斤。

Most experts, though, acknowledge that this rule is too blunt as it fails to account for shifts in the body's metabolism as the kilos pile on.
不过大多数专家都承认，这种方法过于死板，没有考虑到体重增加时体内新陈代谢的变化。

Dr Hall's model tries to do this.
霍尔博士的模式就是要努力克服这一缺陷。

It also accounts for baseline characteristics that differ from person to person.
该模式还将不同人之间的基本特点考虑在内。

Fat and muscle, for example, respond differently to shifts in diet, so the same intake will have one effect on a podgy person and another on a brawny one.
比如，脂肪和肌肉对饮食变化的反应是不一样的，因此同样的摄入量对矮胖子和壮汉的影响也是不一样的。

The result is a more realistic assessment of what someone needs to do to get slim.
结果是对一个人要瘦身必须要做的事情进行了更加现实的评估。

According to the old version, for example, abstaining from a daily 250-calorie bottle of cola would lead to the loss of 35kg over three years.
比如，根据旧模式，每天少喝一罐250卡路里的可乐，三年体重就可以减轻35公斤。

Dr Hall's model predicts an average loss of just 11kg.
而霍尔博士的模式预测只能平均减少11公斤。

Furthermore, it also acknowledges that a dieter's weight will eventually reach a plateau—far more realistic than the old advice,
此外，它还承认节食者的体重最终将到达稳定阶段—比原来的建议要现实得多，

which implied, incorrectly, that weight loss will continue steadily.
原来的建议暗示体重将稳步下降，这是不正确的。

Gaining weight is easy.
增加体重很容易。

A surprisingly small imbalance, just ten extra calories a day, has driven the 9kg jump in the average American's weight over the past 30 years.
非常小的不均衡，不过每天多10卡路里，已经让美国人的平均体重在过去30年内飙升了9公斤。

The reason reversing such gains is hard is that servicing this extra flesh means a person's maintenance diet creeps up with his weight—and so does his appetite.
恢复原来体重很困难的原因是，为增加的体重提供服务意味着一个人保持体能的饮食与其体重一起增加了，其胃口也增加了。

That 9kg increase implies a daily maintenance diet that has 220 more calories in it than three decades ago.
这增加的9公斤意味着每天保持体能的饮食中的卡路里比30年前多220多卡路里。

Returning to the average of the past means reversing every one of those 220 calories. Half-measures will result in a new equilibrium,
恢复到原来的平均水平意味着每个人要减少220卡路里。

but one that is still too heavy.
减少一半就会达成一种新的平衡，这种平衡仍然会太重。

For example, a 23-year-old man who is 170cm tall should weigh 70kg, and be eating 2,294 calories a day.
比如，一位23岁、升高1.7米的男士的标准体重应该是70公斤，每天摄入2294卡路里。

If he actually weighs 110kg he will be eating 3,080 calories to maintain his extra flesh and he thus needs to make a permanent cut of 786 calories from his daily diet if he is to get back to the 70kg desideratum.
如果他的实际体重是110公斤，那么他必须摄入3080卡路里才能承受额外的负担。

If he cuts less than this he will lose some weight,
因此如果他要恢复到70公斤的需要，他必须每天减少固定的786卡路里。

but eventually his intake will match the maintenance level for what he now weighs, and without further cuts his weight will stabilise.
如果他减少的卡路里比这个少，他会减少一些体重，但是最终他的摄入量会与他当前的体重匹配，如果不进一步减少，他的体重将稳定下来。

Someone who weighs 90kg, by contrast, need cut only 435 calories a day to get to his target—a far more manageable proposition.
相比之下，体重90公斤的人只需每天减少435卡路里就可以达到他的目标—这是一个要好办得多的建议。

In principle, the heavier person could make the necessary cuts in stages—reducing his daily intake again and again as he lost weight.
原则上，体重较重的人可以分阶段进行必要的节食—在他体重减轻时，不断减少日常的摄入量。

In practice, that would take a will of iron, and the few people who have such willpower rarely get fat in the first place.
实际上，这需要非常坚定的意志，有这种意志的人几乎根本就不会变胖。

The lesson, then, is to stay, rather than become, slim.
因此，教训就是保持苗条而不是变苗条。

Not easy, in a world whose economic imperative is to satisfy every appetite,
在一个经济动力就是满足每项欲望的世界里，这并非易事，

but perhaps a little more urgent now Dr Hall has put numbers on it.
但是目前霍尔博士用具体数字对它进行了说明，这样或许更加紧迫了些。