【正确答案】Topic: Explanations for Obesity
Conversation
A: Obesity has become one of the most difficult problems either for ordinary people or scientists. In my opinion, the most plausible alternative explanation for the problem is genetic effects. Experts say children of obese mothers are much more likely to become obese themselves later in life.
B: Yes. I think genetic effect is the most powerful factor. Recently I have read a study report that Grand-children of mice fed a high-fat diet grow up fat even if their own mother is fed normally. It means the fate to be obese may have been healed even before one is conceived.
A: Secondly, I think "a little older" also accounts for the increasing obesity problem. Some surveys found out that adults aged 40 to 79 were around three times as likely to be obese as younger people. And with the aging of our society, more and more people are likely to become fat.
B: But nowadays, people pay more attention to physical exercise. They spend more time and money to keep fit and healthy. So, I think "not enough sleep" should be an important reason for obesity. According to data gathered by some experts, people who sleep less than 7 hours a night tend to have a higher body mass index than people who sleep more.
A: Really? It's well known that obesity impairs sleep. Does it work in the other direction?
B: Yes. The U. S. Nurses' Health Study tracked over 6,000 women for 16 years and found that those who slept an average of 5 hours a night gained more weight during the study period than women who slept 6 hours, who in turn gained more than those who slept 7.
A: That sounds reasonable. Besides, I have learnt that climate control has also affected our weight. We have to keep warm and stay cool, which takes energy. However, we choose to live and work in the "thermo-neutral zone" provided by air-conditioners cooling in summer and heating in winter.
B: I agree on this view. Like all warm-blooded animals, we can keep our core body temperatures petty much constant regardless of what's going on in the world around us. We do this by altering our metabolic rate, shivering or sweating, which consumes much energy. But with the development of technology, more and more facilities are designed and produced to keep us in comfortable temperatures. Thus, we use less energy and are more likely to get heavy.
A&B: It's the end of the conversation.