The weight of the average American male today is roughly fifteen perce

Dear avohden
I'm happy to help.

This is a funny question.

The comparative form "fifteen percent more .. than" is not correct. That's why (D) is wrong.

Choices (A) - (C) just slide the word "today" around. I don't think there's a problem with any of the three locations for this word.

The only other split is that (E) includes a subject & verb after "than" for clarity. Certainly (E) is impeccable, but we are allowed to omit all words in parallel & comparison, as long as ambiguity doesn't arise, and I don't believe (A)-(C) are ambiguous in their comparisons. Sometimes omitting the verb after "than" produces gigantic ambiguities, but that's simply not the case here. For example
correct: I like lasagne more than John does.
ambiguous: I like lasagne more than John. This could mean the same as the first, or it could mean that I prefer lasagne to John!
Here, I don't believe any ambiguity arises, because it's clear that "fifty years ago" is a time reference, not a possible term in the comparison. Therefore, four of the five choices would be correct.

I don't find this a very GMAT-like question. The whole sentence is underlined, but despite that, there's exceedingly little difference among the answer choices. A good SC question has one very clear correct answer, and four choices that can be eliminated for absolutely unambiguous reasons.

That's my take.
Mike