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  3. It often seems that some possess superhuman eating powers, allowing them to down an entire pizza while remaining rail-thin. Othe

It often seems that some possess superhuman eating powers, allowing them to down an entire pizza while remaining rail-thin. Othe

admin2019-04-27  40
问题    It often seems that some possess superhuman eating powers, allowing them to down an entire pizza while remaining rail-thin. Others only need to think of a slice and gain five pounds. Now one doctor says there’s evidence that genetics could be behind some of these differences. Regardless of how much you eat, your weight may be out of your hands.
   Vann Bennett, a biochemist at Duke University and his team led a new investigation and discovered why this happens. They engineered mice to have several common modifications of the gene found in humans. They observed that mice who had mutations of ankyrin-B took more glucose (葡萄糖) into their fat cells, which in turn made more fat. Typically, the cell membrane (膜) acts as a barrier to prevent glucose from entering these cells: the alteration kept the gate open.
   The change may serve a useful purpose. "Probably this is not always a bad thing," Bennett told Newsweek. "It could help people survive famines in the past. But today we have so much food that it probably is a bad thing." Our modern diets of fast food drive-thru windows and aisles of packaged snacks make the alteration work against us.
   Dieters have long been told to watch their calories and exercise more, but this new finding suggests that a blanket approach doesn’t work for everyone. And the study illustrates a common problem for people: increased weight gain as a function of age. Our metabolism naturally slows with age, making it harder to maintain the weight of our 30-year-old selves when we’re 50. Now add an unruly ankyrin-B gene, and it may seem impossible to stay slim.
   The mice in the study gained more weight when on high-fat diets. Bennett believes this is because once the fat cells received the glucose and start making more fat, they become sensitive to other fat. Despite being studied in mice, the researchers believe further research on this gene, and possibly others, could potentially create a field of customized diets and health plans based on genetics. Bennett envisions such assessments being performed at birth one day. For now, frustrated dieters can take comfort with one saying: It’s not you, it’s your genes.  
Why is it more difficult to stay slim when we are older?
选项 A、Because we all lack exercise.
B、Because we watch our calories less.
C、Because we have ankyrin-B genes.
D、Because our metabolism slows down.
答案D
解析
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