第十六篇 Eat to Live
A meager diet may give you health and long life, but it’s not much fun — and it might not even be necessary. We may be able to hang on to most of that youthful vigor even if we don’t start to diet until old age.
Stephen Spindler and his colleagues from the University of California at Riverside have found that some of an elderly mouse’s liver genes can be made to behave as they did when the mouse was young simply by limiting its food for four weeks. The genetic rejuvenation won’t reverse other damage caused by time for the mouse, but could help its liver metabolize drugs or get rid of toxins.
Spindler’s team fed three mice a normal diet for their whole lives, and fed another three on half-rations3. Three more mice were switched from the normal diet to half-feed3 for a month when they were 34 months old — equivalent to about 70 human years.
The researchers checked the activity of 11,000 genes from the mouse livers, and found that 46 changed with age in the normally fed mice. The changes were associated with things like inflammation and free radical production一 probably bad news for mouse health. In the mice that had dieted all their lives,27 of those 46 genes continued to behave like young genes. But the most surprising finding was that the mice that only started dieting in old age also benefited from 70 per cent of these gene changes.
"This is the first indication that these effects kick in pretty quickly,” says Huber Warner from the National Institute on Aging near Washington D. C.
No one yet knows if calorie restriction works in people as it does in mice, but Spindler is hopeful. “There’s attracting and tempting evidence out there that it will work,” he says.
If it does work in people,there might be good reasons for rejuvenating the liver. As we get older, our bodies are less efficient at metabolizing drugs, for example. A brief period of time of dieting, says Spindler, could be enough to make sure a drug is effective.
But Spindler isn’t sure the trade-off is worth it. “The mice get less disease, they live longer, but they’re hungry,” he says. “Even seeing what a diet does, it’s still hard to go to a restaurant and say: ‘I can only eat half of that,. ”
Spindler hopes we soon won’t need to diet at all. His company, Lifespan Genetics in California, is looking for drugs that have the effects of calorie restriction.
词汇：
meager adj.不足的
youthful adj.有青春活力的
vigor n.精力，活力
metabolize vt. 使(一种物质)进入新陈代谢过程
genetic adj.基因的
rejuvenation n.恢复活力，返老还童
注释：
1. hang on to ：继续保留。例如：You should hang on to that painting 一 it might be worth a lot of money one day.你应该继续保留那幅画-----或许有一天它会值很多钱。
2. The genetic rejuvenation won’t reverse other damage caused by time for the mouse, but could help its liver metabolize drugs or get rid of toxins：老鼠的肝部基因恢复活力不会逆转老鼠在其他方面的老化，但却有助于肝脏代谢药物或除去毒素。other damage caused by time岁月造成的莫他方面的破坏，即“其他方面的老化”。metabolize drugs：代谢药物，即“使药物参与新陈代谢以提高药效”。get rid of：摆脱，除去。
3. half-ration和half-feed都是指“老鼠饲料正常定量(normal diet)的一半”。
4. free radical production:指体内自由基的产生(形成)。
5. kick in：意为“开始起作用”。 如：We’re still waiting for the air conditioning to kick in.我们还在等着空调开始起作用。
6. be worth it：意为“值得，有益”。如：They are expensive, but they are worth it.那些东西很贵，但划得来。
练习：
1. According to the passage, which of the following is NOT true?
A Eating less than usual might make us live longer.
B If we go on a diet when old, we may keep healthy.
C Dieting might not be needed.
D We have to begin dieting since childhood.
2. Why does the author mention an elderly mouse in paragraph 2?
A To describe the influence of old age on mice.
B To illustrate the effect of meager food on mice.
C To tell us how mice’s liver genes behave.
D To inform us of the process of metabolizing drugs.
3. What can be inferred about completely normally fed mice mentioned in the passage?
A They will not experience free radical production.
B They will experience more genetic rejuvenation in their lifetime.
C They have more old liver genes to behave like young genes.
D They are more likely to suffer from inflammation.
4. According to the author, which of the following most interested the researchers?
A The mice that started dieting in old age.
B 27 of those 46 old genes that continued to behave like young genes.
C Calorie restriction that works in people.
D Dieting that makes sure a drug is effective.
5. According to the last two paragraphs, Spindler believes that A calorie restriction is very important to young people.
B seeing the effect of a diet, people will like to eat less than normal.
C dieting is not a good method to give us health and long life.
D drugs do not have the effects of calorie restriction.
答案与题解：
1. D第一k第一句讲“节食可能不是非做不可的事”，第二句讲“即使上了年纪再节食，我们 仍然有可能在很大程度上保持青春活力”，因此，“我们必须从小就开始节食”是错误的，D是答案。
2. B第二段提及“一只髙龄老鼠”的时候，作者谈到，“只要连续四周限制它进食，它的肝脏基因就会变得和衰老前一样充满活力”。据此，“为了描述节食对老鼠所产生的影响”最好地回答了题干中的问题o
3. D 第四段提到，“正常饲养的老鼠随着年龄的增长有46条肝脏基因会发生变化，这种变化与炎症和有机体组织无限激增有关”，因此，D正确。
4. A第四段最后一个句子讲“但最惊人的发现是那些上了年纪才开始节食的老鼠也能从70%的基因变化中受益”。“最惊人的”自然是“最令研究人员感兴趣的”。
5. C文章的最后两段谈及Spindler对节食的看法。首先，他不能肯定节食是否值得。.其次, 他希望在不久的将来，我们不必节食。所以我们可以推知，他认为节食不是得以健康长寿的好办法。
参考译文
第十六篇 为生存而食
粗茶淡饭或许能给你健康和长寿，但这并不有趣——很有可能也没必要。即便在年老以后才 开始节食我们也能在很大程度上保持住青春活力。
加州大学Riverside分校的斯蒂芬•斯潘德尔及其同事发现，只要连续四周限制一些衰老的老 鼠进食，它们的肝脏基因就会变得和衰老前一样充满活力。虽然老鼠的肝部基因恢复活力不会逆 转它们在其他方面的老化，但是却有助于这些老鼠的肝脏对药物的新陈代谢和清除毒素。
斯潘德尔的队员们一直给其中的三只老鼠正常量的饲料，而给另外三只老鼠正常量饲料的一半，给三只34个月大的老鼠(相当于人类年龄的70岁)喂了一个月的半量饲料，之前这三只老鼠 的饲料量是正常的。
研究者们检查了这些老鼠肝脏的11,000种基因的活性，发现正常饲养的老鼠有46种基因随 年龄的改变而改变。这些改变都与体内自由基的产生有关——这对老鼠的健康来说不是什么好消息。而对于那些终身都在节食的老鼠来说，那46种基因中的27种仍然继续保持着青春活力。但 是最令人吃惊的发现却是那些只是在老年时期节食的老鼠们受益于70%的基因变异。
“这只是第一个这些效果迅速起作用的暗示”，来自华盛顿特区周边的国家老年学学院的哈勃•华纳说。
至今仍然没有人清楚卡路里的控制对人类来说是否如同对老鼠那样有效，但是斯潘德尔对此 充满了希望：“有足以引人注意的证据表明这同样有效。”
如果这确实也对人类有效，我们有理由相信肝脏也可能恢复活力。举个例子，随着我们一天天衰老，我们的身体对药物的新陈代谢越来越没有效率。短时期内的节食，斯潘德尔说到，完全足以保证药效。
但是斯潘德尔并不确定这个方法值得尝试。“老鼠患病少了，寿命延长了，但是它们很饥饿，”他说，“即使能清楚地认识到节食的功效，人们仍然很难在餐馆中说自己只能吃一半的食物。”
斯潘德尔希望我们根本就不用节食。他的公司，加利福尼亚州的寿命遗传学公司，正在寻找有限制卡路里效能的药物
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