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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-rations.Three more mice were switched from the normal diet to half-feed 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-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 percent 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 ol- der,our bodies are less efficient at metabolizing drugs,for example.A brief period of time of die- ting,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.
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.
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第三篇
Eat More, Weigh Less, Live Longer
Clever genetic detective work may have found out the reason why a near-starvation diet
prolonas the life of many animals.
Ronald Kahn at Harvard Medical School in Boston,U.S.,and his colleagues nave
been able to extend the lifespan（寿命）of mice by 18 per cent by blocking the rodent's(啮
齿动物）increase of fat in specific cells.This suggests that thinness一and not necessarily
diet一Iromotes lonq life in"calorie（热量卡）restricted" animals.
"It's very cool work",says aging researche:Cynthia Kenyon of the University ot
California, San Francisc."These mice eat all they want, lose weight and live longer.It's
like heaven."
Calorie restriction dramatically extends the lifespan of organisms as different as worms
and rodents.Whether this works in humans is still unknown,partly because few people are
willina to submit to such a strict diet.
But many researchers hope they will be able to trigger the same effect with a drug once
they understand how less food leads to a longer life.One theory is that eating less reduces
the increase of harmful things that can damage cells.But Kahn's team wondered whether
the animals simply benefit by becoming thin.
To find out, they used biology tricks to disrupt the insulin（胰岛素）receptor (受体)
gene in lab mice一but only in their fat cells."Since insulin is needed to help fat cells store
fat ,these animals were protected against becoming fat,"explains Kahn.
This slight genetic change in a single tissue had dramatic effects.By three months of
age.Kahn's modified mice had up to 70 per cent less body fat than normal control mice,
despite the fact that they ate 55 per cent more food per gram of body weight.
In addition ,their lifespan increased.The average control mouse lived 753 days,while
the thin rodents averaged a lifespan of 887 days.After three years,all the control mice had
died.but one-quarter of the modified rodents were still alive.
"That they ciet these effects by just manipulating the fat cells is controversial,"says
Leonard Guarente of the Massachusetts Institute of Technology,who studies calorie
restriction and aging.
But Guarente says Kahn has yet to prove that the same effect is responsible for
increased lifespan in calorie-restricted animals."It might be the same effect or there might
be two routes to long life,"he points out,"and that would be very interesting."
What can be inferred from the passage about the route to long life?
A.It remains to be studied.
B.It has already been discovered.
C.Eating more leads to long life.
D.Eating less leads to long life.
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Eat for a Good and Healthful Life
Food is essential to us as it_________(1)us alive.But recently,research has
shown that the eating habits of the average Americans may be dangerous to future
________(2).
The foods Americans now choose are often too________(3) in calories（卡路里）
and fats. So this article reports a new study: Diet and Health, Implications（含意）for
Reducing Chronic Disease Risk.
The study,conducted_________(4)the National Research Council's Committee
on Diet and Health,__________(5)that balancing nutrition（营养）,calories and activity
is the_____(6)to enjoying a long and healthful life.
The report recommends that most Americans increase_____(7)activity to a
moderate level and make changes in food__________(8)and the amount of calories
taken to maintain ideal weight.
Most of us-even_________(9)of us at ideal weight-need to eat less fat so
_________(10)no more than 30%of our daily calories will come from fat.
That means cutting _______ ( 1 1 ) on red meat and whole milk dairy（乳制品）
products.Indeed,eat fish,chicken without skin,meats containing little or no fat,and
low-fat or no-fat dairy__________(12).
The report of the Committee on Diet and Health recommends we eat five or more 1/2-
cup servings（一份）of vegetables and fruits___________(13）一especially green and
yellow vegetables and such fruits as oranges and lemons.
Eating more fruits_________(14)vegetables doesn't have to mean taking increased
amounts of calories.Many plant foods are rich in nutritional substances:they provide many
vitamins and minerals for very few__________(15).
_________(15)
A.liquids
B.sugars
C.resources
D.calories
