Calorie restriction, a diet high in nutrients but low in calories, is

OFFICIAL EXPLANATION

A. The passage states that calorie restriction in mice and rats prolongs life by preventing diseases. The human study had much more limited findings – that calorie restriction in moderately overweight humans decreases insulin levels and body temperature. While these traits are known to be associated with longevity, there are no data that link calorie restriction itself to prolonged human life. Additionally, calorie restriction may have other unstated effects, unrelated to longevity. There is no information in the passage that indicates whether these effects are the same in humans as in mice and rats. Finally, the use of the term "humans" is far too general; the study dealt only with moderately overweight humans and so any inference would need to be restricted to this subset of individuals.

B. While the passage indicates that certain traits known to be associated with longevity are found in moderately overweight humans who reduce their calorie intake, this is far removed from the conclusion that calorie intake will actually increase a human's lifespan. Additionally, the use of the term "humans" is far too general; the study dealt only with moderately overweight humans and so any inference would need to be restricted to this subset of individuals.

C. The study observed that individuals with the greatest percentage decrease in their calorie intake demonstrated the greatest decrease in insulin levels and body temperature. This shows a strong correlation between calorie intake and insulin levels. However, this correlation is not necessarily direct. It is possible that this correlation holds, but only up to a point. For example, it might be the case that any reduction in calorie intake over 50 percent does not result in any additional insulin level decreases. Moreover, the passage only draws this correlation for individuals with the greatest percent decrease in calorie intake. It is very possible that individuals with a relatively low decrease in calorie intake exhibit the exact same decrease in insulin levels as individuals with a moderate decrease in calorie intake.

(D) The study makes no reference to the health of individuals who reduce their calorie intake. It tries to draw some connection to the longevity of those individuals, but longevity is not the same as health. An individual could live a very long, unhealthy life.

(E) CORRECT. The passage states that the greatest decrease in insulin levels was observed in individuals with the greatest percentage change in their calorie intake. This means that some individuals in the study reduced their calorie intake by a greater percentage than other individuals in the study. The passage also states that the study participants reduced their individual calorie intakes by "at least 25 percent." Thus, one can safely infer that there were some participants who reduced their calorie intake by more than 25 percent.