英语六级(CET6)阅读理解预测试题及答案(3)_大学英语阅读

英语六级(CET6)阅读理解预测试题及答案(3)

　　Its well known that obesity impairs sleep, so perhaps people get fat first and sleep less afterwards. But the nurses study suggests that it can work in the other direction too: sleep loss may precipitate weight gain.

　　Although getting figures is difficult, it appears that we really are sleeping less. In 1960 people in the US slept an average of 8.5 hours per night. A 2002 poll by the National Sleep Foundation suggests that the average has fallen to under 7 hours, and the decline is mirrored by the increase in obesity.

　　Climate control

　　We humans, like all warm-blooded animals, can keep our core body temperatures pretty much constant regardless of whats going on in the world around us. We do this by altering our metabolic（新陈代新的） rate, shivering or sweating. Keeping warm and staying cool take energy unless we are in the thermo-neutral zone, which is increasingly where we choose to live and work.

　　There is no denying that ambient temperatures（环境温度） have changed in the past few decades. Between 1970 and 2000, the average British home warmed from a chilly 13C to 18C. In the US, the changes have been at the other end of the thermometer as the proportion of homes with air conditionings rose from 23% to 47% between 1978 and 1997. In the southern states where obesity rates tend to be highest the number of houses with air conditioning has shot up to 71% from 37% in 1978.