Q9 - Typically, people who have diets

[lwilliams25619]

Will someone explain this to me? I chose (B), but on closer reading I think I understand why that is wrong. Is it because (B) serves to strengthen the argument as opposed to justifying the conclusion that the author arrived at? Thanks.

[dtangie23]

Breaking down the stimulus...

People with diets high in saturated fat usually have an increased risk of heart disease.

If the saturated fat in their diets is replaced with unsaturated fat, this risk decreases.

The conclusion that the author draws from this is that people who continue to eat all of that saturated fat can reduce their risk of heart disease simply by adding more unsaturated fat to their diets.

Do you see the flaw here? Suppose you already eat an enormous amount of saturated fat. You decide that you want to, on top of this saturated fat, add some unsaturated fat to your diet. Will that decrease your risk of heart disease?

No. The existing amount of saturated fat in your diet needs to be replaced with unsaturated fat in order for the risk to decrease. If this is not the case, the risk for heart disease may not be affected.

(A) shores up this flaw by explicitly stating the above as an assumption.
(B) is irrelevant. So what if it brings other health benefits? The conclusion is specifically about reduced risk of heart disease.

[ManhattanPrepLSAT1]

Great work dtangle23! That's exactly how I see it as well.

[andrea.devas]

I understand why A is the answer but can someone help me knock out C as well? Is it just because the question asks " most helps justify the reasoning above?" Thanks in advance

[mitrakhanom1]

I would also like to know why C is incorrect? If I state diet is the most important factor in determining a person's risk of heart disease wouldn't that help to justify that nothing else could be an alternative reason? Or is it too broad for an answer? Isn't answer A just restating a premise? the second sentence says "those who replace saturated fat in their diets with unsaturated fat decrease their risk of heart disease." I fail to see the difference between the second sentence in the argument and answer choice A. please let me know. thanks.

[ohthatpatrick]

When I first read this argument I thought, "Hmmm, the conclusion sounds like it's actually logically derived. That can't be! They're asking me to strengthen it so it must be flawed somehow."

There must be some way that this conclusion could be wrong, that "increasing your intake of unsaturated fat would NOT lower your risk of heart disease".

Here's the argument:

Diet high in saturated fat -> more risk of HD
+
replace saturated fact with unsaturated fat -> less risk of HD
======
increasing intake of unsaturated fat --> less risk of HD
(for ppl who eat a lot of saturated fat)

Isn't the conclusion just kinda repeating the 2nd sentence?

No, because the second sentence is about replacing saturated fat with unsaturated fat, while the conclusion is about increasing intake of unsaturated fat.

Do you see the difference?

REPLACING:
I already eat 50g of saturated fat a day and then I switch to a diet of 25g saturated / 25g unsaturated. I'm eating less saturated fat; I've lowered my risk of heart disease.

INCREASING INTAKE:
I continue to eat 50g of saturated fat a day and I just add 25g of unsaturated fat on top of that. I'm still eating the same amount of saturated fat; I haven't lowered my risk of heart disease.

If you spot the gap between "replacing" and "increasing intake", then (A) will immediately appeal to you.

(A) says that "increase unsaturated --> decrease saturated"

(B) we don't care about health benefits other than a reduced risk of heart disease. ("other than" is the classic Out of Scope tip-off) The conclusion is only concerned with whether or not we have a reduced risk of heart disease. Any other increased/decreased risks of anything else is completely irrelevant to the truth/falsity of the conclusion.

(C) If this strengthens, it does so ever so mildly, in the sense that we ARE talking about a dietary change: "increasing our intake of unsaturated fat". But this doesn't specifically engage with the premises and it doesn't address the key assumption/flaw in the argument. So it doesn't strengthen nearly as much as (A) does. (A) practically PROVES the conclusion is valid. (C) doesn't come anywhere near doing that. It only tells us that what we're discussing in the premises is relevant to risk of heart disease. Consider for a second that if we said "Exercise is the most important factor in a person's risk of heart disease", it would NOT Weaken the argument in the slightest. The conclusion is only about "would this or wouldn't this have an effect on risk of heart disease?" Even if exercise were the most important factor in a person's risk of heart disease, it's still entirely possible that dietary change CAN also be a factor.

(D) "Life expectancy" is totally out of scope.

(E) The 'difficulty' of making the switch is completely irrelevant to whether or not making the switch would have any effect. Also, we're not talking about moving to a diet that includes little fat. We're ideally talking about moving to a diet that includes less saturated, more unsaturated fat.

Hope this helps.