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  3. For most people, fat is a burden. It doesn’t really matter where it appears, we just don’t want it. But it turns out that our bo

For most people, fat is a burden. It doesn’t really matter where it appears, we just don’t want it. But it turns out that our bo

admin2010-12-04  68
问题       For most people, fat is a burden. It doesn’t really matter where it appears, we just don’t want it. But it turns out that our bodies also make a unique form of fat tissue that behaves remarkably unlike any other: rather than storing excess energy, this fat actually burns through it. It’s called brown fat and health experts confirm for the first time that healthy adults have stores of this tissue, which researchers hope to study further as a potential new weight-loss treatment.
      Human newborns have been known to have any significant deposits of brown fat, so called because of its abnormally high concentration of dark---colored mitochondria (线粒体), the engines that sustain cell activity. The primary purpose of brown fat is to regulate body temperature: the mitochondria-packed cells are designed to burn high quantities of sugar, and release that energy as heat a mechanism that newborns rely on to keep themselves toasty.
      As people age, however, the body becomes better at regulating temperature, so brown-fat stores shrink and white fat starts to emerge. A research team in Sweden has found that healthy adults retain a sizable amount of fat in the front and back of the neck expressing the same proteins as brown fat.
Identifying the presence of brown fat is one thing, but activating it to burn more sugar is another. Two studies confirmed that brown-fat cells become more active in the cold. But before we consider joining the Polar Bear Club, can brown fat actually cause weight loss? Brown fat may indeed allow a person to burn more calories (卡路里) with the same amount of consumption. On the basis of animal models, researchers calculate that 50g of brown fat could burn about 20% daily calorie an average person takes in. Leaner people tended to have more brown-fat deposits than overweight individuals. Interestingly, women were ’twice as likely as men to have active brown fat.
      Still, the findings don’t necessarily mean that activating brown fat leads to a slimmer waist. For one thing, the body is especially good at maintaining balance, which is why a boost in calorie-burning can often make it hunger signal and prompt people to eat more to make up for the loss. And even if drug companies could find a way to activate (刺激) brown fat safely, that excess activity could throw off other metabolic (新陈代谢的) systems and damage your health.  
What is the main idea of Para. 5?
选项 A、Why brown fat can not necessarily help to lose weight.
B、Why people will feel hungry.
C、Why people is eating more food than before.
D、Whether drug companies can manage to activate brown fat.
答案A
解析 主旨大意题。第五段是对上文论述的总结。第一句即为本段中心句，得出的结论是即使激活了棕色脂肪不一定就意味着可以让：你拥有纤细的腰肢，然后列出了两条原因，可见本段主要讲述A)“棕色脂肪不一定能帮人减肥的原因”符合文意，故为答案。
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