经济学人下载:重拾苗条

Science and technology
科学技术

Slim pickings
重拾苗条

Evidence that the problem of obesity starts in the womb
有证据证明肥胖始于子宫

IN THE late 1980s David Barker, a British doctor, suggested that what a woman eats when she is pregnant shapes her child's physiology for life.
上世纪80年代末，英国医生大卫巴克尔说妇女怀孕期间饮食会塑造孩子未来的生理机能。

He called the idea fetal programming.
他称之为胎儿计划。

Such programming would allow an individual to make optimum use of available nutrients, on the assumption that his own diet will be similar to his mother's.
这一计划让每个人以最佳方式利用营养，他假定自己的饮食和母亲的相似。

If it was not similar, though, there could be problems.
如果不相似，就有问题了。

Dr Barker speculated that fetal programming—in mesalliance with the spread of fatty, sugary foods over recent decades—might explain the epidemic of obesity, heart disease and late-onset diabetes that plagues many rich countries.
巴克尔推测胎儿计划与偏远地区普遍的高脂肪，含糖饮食的有关系。这也许就解释了肥胖，心脏病以及折磨很多富裕国家的糖尿病。

It is a neat theory, but hard to prove.
这是很明确的结论，但却很难证明。

On October 29th, though, Sir Peter Gluckman, an endocrinologist and evolutionary biologist at the University of Auckland, in New Zealand, presented evidence to support it at a conference organised in Lausanne by Nestlé, a Swiss food company.
但在10月29日，新西兰奥克兰大学内分泌和进化生物学学家彼得格拉克曼，在瑞士洛桑雀巢食品公司一个会议上提供了证据。

Dr Gluckman carried out his study in Jamaica, in collaboration with Terrence Forrester, of the University of the West Indies.
格拉克曼博士在牙买加进行了试验，并且与西印度大学特伦斯福伦斯特合作。

He picked Jamaica because malnutrition is endemic there.
他选择牙买加是因为营养不良是那里的地方病。

That allows the theory of fetal programming to be tested by finding out whether those who experienced malnutrition in the womb respond differently to food than those who were properly fed.
这样一来，胎儿计划就能通过研究母体内营养不良与营养充足是否影响孩子的食物选择来证明。

Dr Gluckman and Dr Forrester began their study by looking at people who had survived childhood malnutrition.
格拉克曼和福伦斯特从研究儿童营养不良的幸存者开始。

Symptoms normally manifest themselves in one of two ways, known as marasmus and kwashiorkor.
常常表现为一种或两种症状，身体衰弱症和夸希奥科病。

Children with marasmus are simply emaciated.
衰弱症的孩子只是瘦而已。

One significant difference between the two syndromes is that children with marasmus are twice as likely to survive malnutrition as those with kwashiorkor.
夸希奥科病的孩子下腹则膨胀得像电视上那些饥荒浮肿的人。

Dr Gluckman and Dr Forrester looked at 240 people aged between 25 and 40 who had survived one syndrome or the other as children, and found a systematic difference between them.
格拉克曼和福伦斯特博士观察了240个患有综合症的25到40岁之间成人和儿童，发现了二者有规律性的差别。

The marasmus survivors tended to have had low birthweights.
身体衰弱症的患者出生体重偏轻，

The kwashiorkor group had normal birthweights. Low birthweight is an indication of a malnourished mother.
夸希奥科病的人群出生体重正常。出生体重轻就表示母亲营养不良。

Dr Gluckman and Dr Forrester thus hypothesise that the capacity for a marasmus-style response to malnutrition, with its higher survival rate, is programmed into fetuses by maternal malnourishment.
两位博士据此假设身体虚弱消瘦体质是因为营养不良，消瘦体质存活率很高，计入母亲营养不良所致。

Fetuses carried by well-nourished mothers do not, as it were, anticipate the risk of malnutrition, and thus respond to it less well.
福伦斯特博士研究营养充足的母亲则不像营养不良的母亲那么易导致孩子营养不良，孩子也就不容易得消瘦症了。

That suggests fetal programming is a real phenomenon.
这些研究证明胎儿计划确实存在。

But can it help explain obesity, diabetes and so on?
但它能否解释肥胖，糖尿病等病症呢？

To investigate this, the two researchers then offered their volunteers foods that were either high in protein and low in fat, or low in protein and high in fat—but which, crucially, tasted the same, so that they did not know what they were eating.
为了研究这个问题，两位博士又给志愿者食用高蛋白低脂肪或者低蛋白高脂肪的食物，关键的是味道一样，志愿者就不知道自己吃的是什么了。

They found that those who had survived marasmus ate differently from those who had survived kwashiorkor.
他们发现得过消瘦症的人与得过夸希奥科病的人吃的不一样。

The bodies of marasmus survivors seemed to demand more protein in their food.
前者的食物似乎需要更多蛋白质。

When offered a diet low in protein and high in fat, they consumed more of it.
如果给他们低蛋白高脂肪的食物，他们就会吃得更多。

That kept their protein intake constant, but meant they were eating 500 calories a day more than a normal maintenance diet.
以此保证蛋白质的摄入量，同时就意味着他们每天比正常人多摄入500卡路里的食物。

Kwashiorkor survivors did not overeat in this way.
得过夸希奥科病的人就不会这样暴饮暴食。

This, then, may be the key that unlocks the puzzle.
以上就是解开谜团的关键。

Diets of the past would tend to have been lean.
过去的饮食太不平衡了如果时间决定一切，

Anticipating scarcity by overeating in times of plenty would be no bad thing if times of scarcity were a real risk.
短期的饮食过量导致的营养缺乏并不会有严重后果。

Bodies that expected food to be plentiful, by contrast, should ration themselves to avoid the consequences of chronic overeating.
与此相反，对于想吃大量食物的人，则应该约束自己避开长期性饮食过量。

An inability to do that is the price paid for protection from famine by those predisposed to marasmus.
做而易患消瘦症的妇女因为穷又买不起蛋白质足的食物，就没法让自己营养充足了。

This study thus makes a prediction: as diets become high in sugar and fat in places where malnutrition was once common, those who suffered marasmus as children will become overweight more rapidly than those who suffered kwashiorkor.
这项研究预测：在高脂肪高糖类的地区营养不足很常见，那些得消瘦症的人，比如儿童，就会比夸希奥科病患者更快肥胖起来。

If that turns out to be the case, it will be evidence that Dr Barker was right. What is not yet clear is whether the children of today's overfed westerners will experience programming in the opposite direction, and have their appetites restricted.
如果真实情况就是这样，就证明巴克尔教授结论正确。对营养过剩的西方人来说，小孩在母亲肚子里的时候是不是与非洲孩子情况相反，平时是不是注意了饮食限制，目前则尚不清楚。