③ Although the findings of this new study contradict standard dietary advice, they do not come as a surprise to all of the researchers involved. Dr. Rao, one of the study authors, noted that, after 20 years of experience in the field of obesity, he has observed that people who have a regimented lifestyle and diet tend to be thinner and healthier than people with a wide variety of consumption. This anecdotal evidence matches the conclusions of the study, which found no evidence that dietary diversity promotes healthy body weight or optimal eating patterns, and limited evidence shows that eating a variety of foods is actually associated with consuming more calories, poor eating patterns and weight gain. Further, there is some evidence that a greater variety of food options in a single meal may delay people's feeling of fullness and actually increase how much they eat.

④ Based on their findings, the researchers endorse a diet consisting of a limited number of healthy foods such as vegetables, fruits, grains, and poultry. They also recommend that people simultaneously endeavor to restrict consumption of sweets, sugar and red meat. The researchers stress, however, that their dietary recommendations do not imply dietary diversity is never positive, and that, in the past, diversity in diets of whole, unprocessed food may have actually been very beneficial.

1.1.What has been a standard piece of dietary advice for decades?

A People should diversify what they eat.

B People should have a well-balanced diet.

C People should cultivate a healthy eating habit.

D People should limit calorie intake to avoid obesity.

解析：选A。A 细节理解题。依据文章第①段第一句：“The suggestion that people should aim for dietary diversity by trying to eat a variety of foods has been a basic public health recommendation for decades in the United States and elsewhere.” 这句话明确指出，几十年来，建议人们通过多样化饮食来实现膳食多样性一直是公共卫生的基本推荐。因此，正确答案是A。

2.2.What did the new research by the American Heart Association find?

A Unhealthy food makes people gain weight more easily.

B Dietary diversity is positively related to good health.

C People seeking dietary diversity tend to eat more.

D Big eaters are more likely to become overweight.

解析：选C。C 细节理解题。依据文章第①段第四句：“Researchers reviewed all the evidence published related to dietary diversity and saw a correlation between dietary diversity and a greater intake of both healthy and unhealthy foods.” 这句话表明，研究发现膳食多样性与更多的食物摄入量有关，而后面进一步提到这可能导致肥胖。因此，正确答案是C。

3.3.What could help to explain the contradiction between the new findings and the common public health recommendation?

A There is little consensus on the definition of dietary diversity.

B The methods researchers use to measure nutrition vary greatly.

C Conventional wisdom about diet is seldom supported by science.

D Most dietary guidelines around the world contradict one another.

解析：选A。A 推理判断题。依据文章第②段第二句：“But this advice does not seem to be supported by science, possibly because there is little agreement about the meaning of ‘dietary diversity’, which is not clearly and consistently defined.” 这句话说明，新研究与传统建议之间的矛盾可能是因为对“膳食多样性”的定义缺乏共识。因此，正确答案是A。

4.4. What did Dr. Rao find after 20 years of research on obesity?

A There is no clear definition of optimal eating patterns.

B Diversified food intake may not contribute to health.

C Eating patterns and weight gain go hand in hand.

D Dietary diversity promotes healthy body weight.

解析：选B。B 细节理解题。依据文章第③段第二句：“Dr. Rao, one of the study authors, noted that, after 20 years of experience in the field of obesity, he has observed that people who have a regimented lifestyle and diet tend to be thinner and healthier than people with a wide variety of consumption.” 这句话表明，Dr. Rao发现，饮食多样化的人不如饮食规律的人健康。因此，正确答案是B。

5.5. What does the passage say about people who eat a great variety of food?

A They are more likely to eat foods beneficial to their health.

B They don’t have any problems getting sufficient nutrition.

C They don’t feel they have had enough until they overeat.

D They tend to consume more sweets, sugar and red meat.

解析：选C。C 推理判断题。依据文章第③段最后一句：“Further, there is some evidence that a greater variety of food options in a single meal may delay people’s feeling of fullness and actually increase how much they eat.” 这句话表明，食物种类多会延迟人们的饱腹感，导致他们吃得更多。因此，正确答案是C。