CR - Calorie restriction

SubratGmat2011 wrote:Calorie restriction, a diet high in nutrients but low in calories, is known to prolong the life of rats and mice by
preventing heart disease, cancer, diabetes, and other diseases. A six-month study of 48 moderately overweight
people, who each reduced their calorie intake by at least 25 percent, demonstrated decreases in insulin levels and
body temperature, with the greatest decrease observed in individuals with the greatest percentage change in their
calorie intake. Low insulin level and body temperature are both considered signs of longevity, partly because an
earlier study by other researchers found both traits in long-lived people. If the above statements are true, they
support which of the following inferences?
"¢ Calorie restriction produces similar results in humans as it does in rats and mice.
"¢ Humans who reduce their calorie intake by at least 25 percent on a long-term basis will live longer than they would
have had they not done so.
"¢ Calorie intake is directly correlated to insulin level in moderately overweight individuals.
"¢ Individuals with low insulin levels are healthier than individuals with high insulin levels.
"¢ Some individuals in the study reduced their calorie intake by more than 25 percent.

This question is asking for an inference. An inference should be based on the statements of the passage but should go a step further. The facts in the stimulus are true and should guide us.

Looking at the choices;
A - It says "humans" which implies "all humans" whereas it was tested on "moderately overweigth humans". Hence discard.
B - Same as A, discard.
C - Looks good as is given in the stimulus, but one issue here is that it is "unidirectional". We know when calorie intake decreases insulin decreases, but we are not sure what happens when calorie intake is increased, a correlation should imply it should increase, but this fact is not supported by the passage. This makes me leery of the choice. Still I keep it.
D - Health does not equal long life and again as in A not "individuals" it is a sub group (moderately overweight), discard.
E - This is supported by the facts in the stimulus, as the individuals with greatest decrease in calorie intake showed greatest decrease in insulin intake. All individuals decreased intake by atleast 25%, hence atleast one person has to decrease intake of calories by more than 25% or this can not be observed.

Thus between C and E, E is more robustly supported by the facts given.

[spoiler]Hence pick E[/spoiler]

There are two ways of looking at this, in order to make the question tough it is almost overdone, since E almost feels like a restatement of facts. On the other extreme it can be seen as a good question that does not have a straight answer.

What is the source?