I’m going to consider this Horror the third in the Unnecessary Sentences sequence, although it could arguably stand alone.
Here it is in all its glory:
“When one eats fast food, the oil, fat, sugar, salt, and other contents of the food go directly into the body.”
Where else it might go first I cannot imagine, unless “eating” can include “spilling on tie,” “playing with on dish,” and “putting in the refrigerator for later,” all of which activities do involve a detour between bag and mouth. But once it’s in the mouth, food can pretty much be said to have gone directly into the body (assuming no physical abnormality of the mouth).
I THINK my student meant that all those “contents” are broken down into substances that will enter and affect the various systems and components of the body—structurally kind of like the lament sometimes heard at birthday parties, “That cupcake will go directly to my hips,” an hyperbolic utterance bemoaning the speaker’s propensity for putting on fat. As in that example, so for my student: it’s enough to say the “contents” of food go directly into the body; the intermediate steps can be assumed. But if that’s what she means, how is fast food different from other foods?
She might mean that we should worry because fast food contains excessive amounts of things that are bad in excess—oil, fat, sugar, salt—and we are putting those things into our bodies. That would be a likely idea in an essay about the unhealthy effects of a McDonald’s diet, and that’s what this essay was. But that isn’t what she has offered the reader. Maybe she thought the worry part was obvious.
And of course it is. Of course I knew what she meant. How to prevent invasion by these substances? When you eat fast food, this happens—so don’t eat fast food. And that was her essay’s message, so maybe the sentence is doing its job, sort of, after all.
But I’m still sitting here thinking about ways in which food might go into the mouth and then take some side excursion before entering the body. And I don’t really want to think about it!

Well, I wish I hadn’t decided to put a picture in here. Now I’m hungry. But if I eat this food, will it go directly into my body? Image from http://en.wikipedia.org/wiki/Western_pattern_diet