If you're 70 and overweight, you may live longerA few extra pounds might help you live lon

If you're 70 and overweight, you may live longer
A few extra pounds might help you live longer if you're past your prime(壮年) but otherwise healthy, a new study finds.
Physicians routinely follow guidelines issued by the World Health Organization. Because weight depends on height, they use a standard measure called body mass index (BMI), which is calculated as the weight in kilograms divided by the height in meters squared.
Healthy weight is defined as a BMI anywhere between 18.5 and 24.9 in adults, whereas 25 to 29.9 is overweight and 30+ is obese.
The new study suggests that in the elderly, these boundaries may be too narrow. While no one is questioning that extra fat poses health risks in young and middle-aged adults, it may reduce the impact of frailty and old age, geriatrician(老年医学专家) Dr. Thomas Yoshikawa told Reuters Health.
So far, nobody knows exactly how BMI affects lifespan in older people. Some researchers speculate that it acts as an energy reserve that can help the elderly cope with illness.
For the study, Australian researchers followed more than 9,000 men and women who were between 70 and 75 years old at the beginning. The participants reported their height and weight as well as various factors related to health and lifestyle. About 33 percent of the women and 44 percent of the men were overweight.
Over 10 years, more than 2,000 of the participants died. Women who had an active life and didn't smoke were the most likely to be alive at the end of the study.
But neither health nor lifestyle could fully explain why overweight people of both sexes survived longer than their normal-weight peers, who fared no better than obese individuals. In terms of survival, the best BMI was between 26 and 27, well within the overweight range.
The new results agree with earlier research showing that fat may be beneficial in old age.
1．We can learn from the passage that    ．
A. the heavier one is, the better             
B. we shouldn’t lose weight when old
C. one should keep his weight within the remended range
D. we shouldn’t worry about our weight if we are slightly fatter than normal when old 
2．According to the passage, if a person is 1.5 metres in height and 67.5 kg in weight, his BMI is    .
A．30            B．25           C．45         D． 28
3. What does the author want to tell us most?
A. Fatness has little to do with diseases in old age.        
B. Fatness is not always bad.
C. Fatness may be beneficial instead of harmful in old age.
D. Overweight people of both sexes survive longer than their normal-weight peers.D