根据短文回答 41～45 题。 Eat More, weigh Less, Live Longer Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals. 'It's very cool work，'says aging researcher Cynthia Kenyon of the University of California，San Francisc0.'These mice eat all they want.10se 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 willing 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—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 t0 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 get these effects by just manipulating the fat cells is controversial，'says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and agin9. But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted anima.1s.'It might be the same effect or there might be two routes to long life，'he points out，'and that would be very interesting.' 第 41 题 Ronald Kahn and his colleagues can make mice live longer by（ ）.