Dieting, according to an old joke, may not actually make you live longer, but it sure feels that way. Nevertheless, evidence has been accumulating since the 1930s that calorie restriction—reducing an animal’s energy intake below its energy expenditure—extends lifespan and delays the start of age—related diseases in rats, dogs, fish and monkeys. Such results have inspired thousands of people to put up with constant hunger in the hope of living longer, healthier lives. They have also led to a search for drugs that mimic the effects of calorie restriction without the pain of going on an actual diet.
Amid the trend, it is easy to forget that no one has until now shown that calorie restriction works in humans. That omission, however, changed this month, with the publication of the initial results of the first systematic investigation into the matter. This study took 48 men and women and assigned them randomly to either a control group or a calorie—restriction regime. Those in the second group were required to cut their calorie intake for six months to 75% of that needed to maintain their weight.
The study is a landmark in the history of the field, because its subjects were either of normal weight or only slightly overweight. Previous projects have used individuals who were clinically fat, thus confusing the unquestionable benefits to health of reducing fatness with the possible advantages of calorie restriction to the otherwise healthy.
At a molecular level, it suggests these advantages are real. Those on restricted diets showed drops in body temperature and blood—insulin levels—both phenomena that have been seen in long—lived, calorie—restricted animals. They also suffered less damage to their DNA.
Eric Ravussin, of Louisiana State University, says that such results provide support for the theory that calorie restriction produces a metabolic adaptation over and above that which would be expected from weight loss alone. Nevertheless, such metabolic adaptation could be the reason why calorie restriction is associated with longer lifespan in other animals—and that is certainly the hope of those who, for the past 15 years, have been searching for ways of triggering that metabolic adaptation by means other than semi-starvation.
The search for a drug that will delay old age is itself as old as the hills—as is the wishful thinking of the suckers who finance such efforts. Those who hope to find it by mimicking the effect of calorie restriction are not, however, complete snake-oil salesmen, for there is known to be a family of enzymes, which act both as sensors of nutrient availability and as regulators of metabolic rate. These might provide the necessary biochemical link between starving and living longer.
1. We learn from the first two paragraphs that ( ).
2. The word “landmark” (Line 1, Paragraph 3) probably means( ).
3. The results of previous research on the effects of calorie restriction are unconvincing because ( ).
4. It can be inferred from paragraph 5 that people( ) .
5. People might take enzymes as a substitute for calorie restriction in that ( ).
问题1选项
A.people are crazy about dieting in order to lose some weight
B.experimental results show that dieting can prolong animals’ life
C.in the study, two groups of people were asked to go on a diet
D.few results have been worked out on the effects of calorie restriction
问题2选项
A.an event of much profit
B.an event of great excitement
C.an event of great significance
D.an event of unique features
问题3选项
A.the subjects of the research were either of overweight or slightly underweight
B.calorie-restricted animals showed different physical signs in the research
C.the decrease in body temperature may result from changes of outside temperature
D.people cannot tell the benefits of losing weight from those of calorie restriction
问题4选项
A.have been engaged in the study of the replacement of calorie restriction
B.have been looking for drugs that can prolong humans’ life for ages
C.can expect a change in their metabolic rate when going on a diet
D.may benefit from metabolic adaptation in that it may protect their DNA
问题5选项
A.they establish a chemical link between starving and living long
B.they can provide people with enough nutrition
C.they work in a similar way that calorie restriction does
D.they are favored by people who finance the drug research
第1题:B
第2题:C
第3题:D
第4题:C
第5题:C
1.【试题答案】B
【试题解析】细节事实题。定位到文章第一段“Nevertheless, evidence has been accumulating since the 1930s that calorie restriction—reducing an animal’s energy intake below its energy expenditure—extends lifespan and delays the start of age—related diseases in rats, dogs, fish and monkeys. 尽管如此,自20世纪30年代以来,越来越多的证据表明,在老鼠、狗、鱼和猴子身上实行卡路里限制——将动物的能量摄入降低到低于其能量消耗——可以延长寿命,并延缓衰老相关疾病的发生。”可知之前相关的研究表明节食可以延长动物的寿命。所以选项B为正确答案。
2.【试题答案】C
【试题解析】语义推测题。定位到文章第三段“The study is a landmark in the history of the field, because its subjects were either of normal weight or only slightly overweight. 这项研究是该领域历史上的里程碑,因为它的研究对象要么体重正常,要么只是稍微超重。”landmark在这里是有“里程碑的事件”的意思,和C选项“具有重大意义的事件”意义相近。因此选项C正确。
3.【试题答案】D
【试题解析】细节事实题。定位到文章第三段“Previous projects have used individuals who were clinically fat, thus confusing the unquestionable benefits to health of reducing fatness with the possible advantages of calorie restriction to the otherwise healthy. 由于以往的研究对象都是临床肥胖研究者,因此人们会把减肥对健康毋庸置疑的好处与限制卡路里摄入量对健康人群可能带来的好处混淆在一起。”由这句话我们可以得知人们常常会把减肥的好处和限制卡路里的摄入混在一起,区分不清。这样也就造成了之前的研究不是很确定。故正确答案选D。
4.【试题答案】C
【试题解析】推理判断题。定位到文章第五段“Nevertheless, such metabolic adaptation could be the reason why calorie restriction is associated with longer lifespan in other animals—and that is certainly the hope of those who, for the past 15 years, have been searching for ways of triggering that metabolic adaptation by means other than semi-starvation. 然而,这种代谢适应可能就是为什么限制热量摄入与延长动物寿命有关的原因——这当然也是在过去15年里一直在寻找除半饥饿之外触发这种代谢适应方法的人的希望。”结合上下文推断,这里主要是节食过程中,动物身上的新陈代谢发生变化。和选项C的意思基本相符。
5.【试题答案】C
【试题解析】细节事实题。定位到文章最后一段“Those who hope to find it by mimicking the effect of calorie restriction are not, however, complete snake-oil salesmen, for there is known to be a family of enzymes, which act both as sensors of nutrient availability and as regulators of metabolic rate. 那些希望通过模拟限制卡路里的作用来研制药物的人,他们并非完全只是些江湖郎中,因为已知有一组酶,它们既是营养可用性的传感器,又是代谢率的调节者。”由此可知这里由于酶能够抑制热量的产生,它可能会作为一种替代热量限制的作用的药物来研发出来,作为延长人类寿命的药。因此选项C正确。