Bunuel wrote:
In a study, one group of volunteers was fed a high-protein, low-carbohydrate diet; another group was fed a low-protein, high-carbohydrate diet. Both diets contained the same number of calories, and each volunteer’s diet prior to the experiment had contained moderate levels of proteins and carbohydrates. After ten days, those on the low-carbohydrate diet had lost more weight than those on the high-carbohydrate diet. Thus, the most effective way to lose body fat is to eat much protein and shun carbohydrates.
Which one of the following, if true, most weakens the argument above?
(A) A low-protein, high-carbohydrate diet causes the human body to retain water, the added weight of which largely compensates for the weight of any body fat lost, whereas a high protein, low-carbohydrate diet does not.
(B) Many people who consume large quantities of protein nevertheless gain significant amounts of body fat.
(C) A high-protein, low-carbohydrate diet will often enable the human body to convert some body fat into muscle, without causing any significant overall weight loss.
(D) In the experiment, the volunteers on the high carbohydrate diet engaged in regular exercise of a kind known to produce weight loss, and those on the low-carbohydrate diet did not.
(E) Many of the volunteers who had been on the low-carbohydrate diet eventually regained much of the weight they had lost on the diet after returning to their normal diets.
EXPLANATION FROM Fox LSAT
The first problem I see with the logic here is that the conclusion goes way off the rails with “the most effective way.” The study only compared two groups: high-carb/low-protein vs. low-carb/high-protein. How can the conclusion possibly say “the most effective way,” if it only looked at two ways? In order to make that conclusion, you would have had to study every possible method of losing body fat!
We’re asked to weaken the argument, and the above features such a huge problem with the reasoning that we should start by looking for that particular issue in one of the answer choices. If we can’t find it, then we’ll reconsider and look for another flaw.
A) This isn’t what we’re looking for, but it still might be worthy of consideration. Let’s get through the rest of the answer choices and if something awesome doesn’t jump out at us, we’ll come back to this one.
B) Well, yeah. Of course you can ruin your diet by “consuming large quantities of protein” alongside large quantities of carbs, fat, alcohol, and everything else. If you do that, you’re going to gain body fat. But that’s not the point of the study, because the study was about two groups that were on a fixed total caloric intake. No way is this it.
C) This would only strengthen the idea that the high-protein/low-carb diet is good for lowering body fat. We’re looking for a weakener, so this is out.
D) This would also strengthen the argument, not weaken it. If the high-carb people were also exercising, and they didn’t lose weight, then this would support the idea that low-carb is superior. We’re looking for a weakener, so this is out.
E) Regaining the weight is simply irrelevant. The conclusion of the argument wasn’t about keeping fat off, it was only about losing fat in the first place. No way.
I didn’t find exactly what we were looking for, but I really hate B through E. So now we can reconsider A. Here’s my case for it: If it’s true that the low- protein/high-carb diet causes you to retain water, then it’s possible that your body
did lose fat even if you didn’t lose weight. The conclusion of the argument wasn’t about losing weight, it was about losing fat. If A is true, then it’s possible that the low-protein/high-carb diet was actually better than the high-protein/low-carb diet for losing fat. That’s the best weakener of the bunch.
So A is our answer
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