9．Is a recently discovered hormone the reason why folks who lose weight can't keep it off？
Like millions of other fat people，at 530inches high，more than 300pounds，Carnie Wilson was not just fat．After trying all sort of diets that didn't work，she has to go to the stomach-bypass surgery （胃部迂回手术），ie，have most of her stomach sewed up，only leaving tiny room to hold several tablespoonfuls at most．Result：she simply couldn't eat the way she used to．In three years，Wilson is one third of her former weight．
Wilson's experience is not all that unusual，and while doctors still aren't exactly sure what is going on，a report in last week's Journal of Medicine offers an explanation．The loss of appetite in bypass patients may be linked to a recently discovered hormone called ghrelin．Not only that，ghrelin may turn out to be one reason we feel hungry and it's hare for didters to keep weight off．
Nowadays，researchers are careful to stress only what they know for sure．For the three conclusions，the leading Dr．David of the University of Washington says，"I feel very solid about two of them．"The first is that ghrelin levels in the bloodstream rise significantly before meals and drop afterward．The second conclusion is that ghrelin levels are higher on average in people who have lost weight from dieting．
Dr．David is less sure of the third conclusion，that bypass patients have only a quarter as much ghrelin as most people of normal weight．After all，ghrelin is produced by cells in the stomach．Years ago，leptin，a hormone was found as an appetite suppressant （食物抑制剂）．But after years of trying，it had to be given up．
What doctors suspect is that both leptin and ghrelin are part of a complex system of brain and body chemicals that govern weight and appetite．That does not mena pharmaceutical （药物的） weight control is forever out of the question．"In the next ten years，we will be able to develop new drugs to help people lose weight healthily and effectively．"
47．What can we learn about ghrelin according to the passage？D
A．After meals ghrelin levels are higher in the bloodstream．
B．People who have lost weight have less ghreilin in their body．
C．Without ghrelin，people are really difficult to lose weight．
D．Ghrelin is something produced by cells in the stomach．
48．What is Dr．David not sure？B
A．pharmaceutical weight control is impossible．
B．There is less ghrelin in the bypass patients．
C．new drugs will be developed in 10years．
D．ghrelin levels are higher in people on diet．
49．In fact，people's weight and appetite are controlled byC
A．ghrelin and leptin B．hormone and medicine
C．brain and body chemicals D．stomach and food
50．What can we infer from the passage？C
A．People with a lower ghrelin level go hungry easily．
B．Doctors managed to use leption to control the appetite．
C．Doctors are optimistic about how to lose weight healthily．
D．The loss of appetite in bypass aptient is linked to leptin．
分析 本文属于说明文阅读，作者通过这篇文章主要向我们描述了最近发现的荷尔蒙可以使人减肥但不能保持，医生发现这是胃部产生的一种化学物质，可以减肥，而医生也对未来人类的健康减肥很有信心．
解答 47．D．细节理解题．根据文章倒数第二段"After all，ghrelin is produced by cells in the stomach"可知这种细胞是由胃部产生的；故选D．
48．B．细节理解题．根据文章倒数第二段"Dr．David is less sure of the third conclusion，that bypass patients have only a quarter as much ghrelin as most people of normal weight"可知戴维博士不确定是旁路手术患者．有较少的Ghrelin；故选B．
49．C．细节理解题．根据文章最后一段"What doctors suspect is that both leptin and ghrelin are part of a complex system of brain and body chemicals that govern weight and appetite．That does not mena pharmaceutical （药物的） weight control is forever out of the question"可知人们的体重和食欲是由大脑和体内的化学物质控制的；故选C．
50．C．推理判断题．根据文章最后一段"In the next ten years，we will be able to develop new drugs to help people lose weight healthily and effectively"可知医生对如何减肥很乐观；故选C．
点评 考察学生的细节理解和推理判断能力，做细节理解题时一定要找到文章中的原句，和题干进行比较，再做出正确的选择．在做推理判断题不要以个人的主观想象代替文章的事实，要根据文章事实进行合乎逻辑的推理判断．
