Help me understand this LR question

[Nylo]

I've gone over this a hundred times but for some reason I have a mental block against accepting the credited response (even though all the other choices are worse). Maybe one of you can hit upon the magic combination of words that will explain this in a way that I can understand...


June 2001 LSAT / Section 2 / Question 17

Dietary researcher: A recent study reports that laboratory animals that were fed reduced-calorie diets lived longer than laboratory animals whose caloric intake was not reduced. In response, some doctors are advocating reduced-calorie diets, in the belief that North Americans' life spans can thereby be extended. However, this conclusion is not supported. Laboratory animals tend to eat much more than animals in their natural habitats, which leads to their having a shorter life expectancy. Restricting their diets
merely brings their caloric intake back to natural, optimal levels and reinstates their normal life spans.
 
Which one of the following, if true, would most weaken the dietary researcher's argument?
 
(A) North Americans, on average, consume a higher number of calories than the optimal number of calories for a human diet.
(B) North Americans with high-fat, low-calorie diets generally have a shorter life expectancy than North Americans with low-fat, low-calorie diets.
(C) Not all scientific results that have important implications for human health are based on studies of laboratory animals.
(D) Some North Americans who follow reduced-calorie diets are long-lived.
(E) There is a strong correlation between diet and longevity in some species of animals.
 
Credited response: A

Just *how* does (A) weaken the dietary researcher's argument? It seems to strengthen the analogy between North Americans' dietary habits and laboratory animals' dietary habits, so if North Americans also consume a higher number of calories than the optimal number for a human diet just like laboratory animals eat much more than animals in their natural habitats, then this also leads to North Americans having a shorter life expectancy. Thus, putting North Americans on reduced-calorie diets will only bring their caloric intake back to natural optimal levels and merely reinstate their normal life spans instead of extending it. Isn't this basically what the dietary researcher is saying?

[Ginatio]

as I understand it, the dietary researcher's final point is that the correlation between laboratory animals and humans is not enough to justify the proposal that humans should reduce their calorie intake in order to extend their lifespan. the reason he's saying the correlation is not supported is because lab animals are known to eat more and take in more calories than their counterparts on a natural diet in the wild.

this rejectection of the correlation between humans and lab animals can be traversed by recognizing that humans also take in more calories than what would be a "natural" diet.

so, (A) supports the correlation between lab animals and north americans, which the dietary researcher had rejected as having a caveat... thus, (A) weakens the dietary resesarcher's argument

[buster]

The dietary researcher was claiming that the analogy didn't apply because the lab animals consumed more than the optimal calories. If the North Americans also consumed more than the optimal calories, that invalidates that portion of the researcher's argument and the analogy therefore holds true.

Or at least that's the way I read it.

[buster]

beat me to it, Ginatio

[spacecowgirl]

as I understand the argument, the low calorie diet "reinstates the normal life span" of laboratory animals.  that means extends it back to normal.  the argument that doctors are making isn't that a low-calorie diet will help north americans live longer than everyone else, only that it will help them live longer than they already do. so the fact that lab rats typically do not live as long as rats in their natural habitat is irrelevant.  all that matters is that reducing the number of calories they eat makes them live longer.

so, if north americans eat a higher number of calories than is optimal, then eating a low-calorie diet should help extend their life span, too, regardless of what it is relative to people who eat an optimal number of calories.

does that make sense?

[jonathanK]

I think that the word restrict is a little misleading in this question.  Restrict typically means to make less.  In this case it means to eliminate the foods that that make it impossible for optimal health.  In the case of the animals, it means giving them more of the foods they need.

Also, the goal here is to restore the natural optimal levels so their normal life spans can be reinstated.  Now let's take a look at choice A.

If we are to believe that humans eat more than the optinmal level of calories, reducing the calories would bring them back to the optimal levels.  That makes A the correct choice

[maxse]

I think that the word restrict is a little misleading in this question.  Restrict typically means to make less.  In this case it means to eliminate the foods that that make it impossible for optimal health.  In the case of the animals, it means giving them more of the foods they need.

Also, the goal here is to restore the natural optimal levels so their normal life spans can be reinstated.  Now let's take a look at choice A.

If we are to believe that humans eat more than the optinmal level of calories, reducing the calories would bring them back to the optimal levels.  That makes A the correct choice

Exactly! So doesnt that support and not weaken the argument?

[maxse]

I think that the word restrict is a little misleading in this question.  Restrict typically means to make less.  In this case it means to eliminate the foods that that make it impossible for optimal health.  In the case of the animals, it means giving them more of the foods they need.

Also, the goal here is to restore the natural optimal levels so their normal life spans can be reinstated.  Now let's take a look at choice A.

If we are to believe that humans eat more than the optinmal level of calories, reducing the calories would bring them back to the optimal levels.  That makes A the correct choice

Exactly! So doesnt that support and not weaken the argument?

[brirobs]

Exactly! So doesnt that support and not weaken the argument?

You have to be really careful about what the argument actually is.  The author's argument is that reducing calorie intake will not be beneficial to humans.  Answer (A) insists that reducing calorie intake would indeed be beneficial to humans.

[maxse]

hmm I see. Could u highlight wihch part makes that conclusion. Im having a bit of a tough time. this is def a tough question, right?

I mean hes just saying that those animals are being brought down to their normal eating habits, so its not really extending their life but bringing it back to normal? hmmmm