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      Weighing too much can damage your health, and obesity is a growing problem for both kids and

adults around the world.

     Sleep might be one answer to the problem.A new study has found that elementary school students

who slept too little were more likely to gain pounds.In the United States today, some 9 million children

over the age of 6 are obese (too fat).

     Past studies have shown a link between sleeping less and weighing more, but scientists have had a

tough time determining"which_came_first, the_chicken_or_the_egg", says Julie C. Lumeng of the

University of Michigan in Ann Arbor.In other words, it hasn't been clear whether kids who weigh too

much have trouble sleeping, or whether sleeping less leads to weight gain.Both scenarios (情况) seemed

equally possible.

      To get a better idea of which causes which, Lumeng and his colleagues interviewed the parents of

785 third graders from around the United States.The parents answered questions about how well their

kids slept that year.Three years later, the parents answered the same questions.By sixth grade,18

percent of kids involved in the study were obese.The scientists found no relationship between weight

and the students'race or gender.It also didn't matter how strict their parents were.Obesity struck all of

these groups equally.

     Instead, sleep seemed to be the key factor.Over the 3 years of the study, the children averaged a

healthy 9.5 hours of sleep a night.Some kids, however, slept a lot more-or less-than others.For the sixth

graders, every hour of sleep above the 9.5hour average was linked to a 20 percent lower risk of being

obese.Sleep appeared doubly important for the third graders.Every extra hour of sleep they got was

linked to a 40 percent drop in obesity by third grade.

     "I expected we'd find that this (sleep link with obesity) was just a_bunch_of_bunk, " says Lumeng,

a pediatrician.But their findings were convincing.No matter how her team looked at the link, "we

couldn't make it go away."

1. According to the research, ________.

A. 9 million people in America have a weight problem

B. not enough sleep contributes to a gain in weight

C. sixth graders need more sleep than third graders

D. lack of sleep has become the most deadly killer

2. The statement "which came first, the chicken or the egg" suggests that________.

A. scientists are sure about the causes of children's obesity

B. it's easy to decide the cause and effect of this problem

C. scientists are still confused about the cause and effect of the problem

D. you'll develop obesity if you eat chicken and eggs

3. Recent studies show that a child's weight is influenced by the________.

A. amount of sleep  

B. parents'attitude to him

C. race or gender  

D. performance in school

4. The underlined part in the last paragraph most probably means something________.

A. acceptable  

B. understandable

C. reliable  

D. unreasonable