Ⅰ.阅读理解
阅读下列材料，从每题所给的四个选项(A、B、C和D)中，选出最佳选项。
Researchers are generally divided not only on what causes obesity, but also on why we feel hungry and often fail to stay on a diet.
The conventional thinking, held by the majority of researchers and clinicians I've interviewed over the years, is that obesity is caused by extra calories. They refer to it as an “energy balance” disorder, and so the treatment is to consume less energy (fewer calories) and expend more. When we fail to maintain this goal, the implication is that we simply lack willpower or selfdiscipline.
The minority's position in this field—one that Dr. Ludwig holds, as do I after years of reporting—is that obesity is actually a hormonal regulatory disorder, and the hormone (激素) that dominates this process is insulin (胰岛素). It directly links what we eat to the accumulation of extra fat and that, in turn, is tied to the foods we long for and the hunger we experience. It's been known since the 1960s that insulin signals fat cells to accumulate fat, while telling the other cells in our body to burn carbohydrates (碳水化合物) for fuel.
If you promote insulin levels even a little, says Dr. Robert Lustig, a pediatric endocrinologist at the University of California, San Francisco, the body will switch over from burning fat for fuel to burning carbohydrates, by necessity.
“The more insulin you release, the more you need carbs，” he said. “Once you're exposed to a little carbohydrate, you get an insulin rise from it. And you compensate by particularly getting hungry for more carbohydrate. A high insulin level drives a thirst for carbs.”
The result is that even a bite or a taste of carbohydraterich foods can stimulate insulin and create a hunger—a thirst—for even more carbohydrates. “There's no question in my mind，” says Dr. Lustig, “that once people who are ‘carboholics’ get their insulin levels down, they become less fond of carbs. And if they fall off the wagon and start eating carbs, they go right back to where they were before. I've seen that in numerous patients.”
1．What kind of problem causes people's energy unbalance according to traditional thinking?
A．The psychological problem.
B．The biological problem.
C．The social problem.
D．The medical problem.
2．What does the author think leads to obesity?
A．Surplus calories. B．High insulin levels.
C．Lack of exercise. D．Low hormone levels.
3．According to Dr. Lustig，taking carbohydraterich foods may result in ________.
A．fat accumulation
B．desire for more food
C．fat consumption
D．less insulin releasing
4．What may researchers of both sides think important in fighting obesity?
A.Training our willpower.
B．Keeping energy balance.
C．Staying on a chosen diet consistently.
D．Maintaining hormonal regulatory order.
