Generally speaking, these topics would make a great single-paged essay. However, we need the queston (presumably the headline) that will have enough information to cover 4-5 pages of detail.
"How do French Fries affect the brain?"
This is a good question, but will probably only get 2-3 pages complete at maximum due to it lacking in variety.
"As of last year, how many obese adults in the US were also once obese children?"
This is also a good question, but only covers a year's worth of work, which will lack in detail to suffice for 4-5 pages.
"What Causes Childhood Obesity?"
This question is excellent for a 4-5 page research paper. It has a variety of reasons to answer, and it can provide explanations with side-notes for each branch of information that connects to the factors of childhood obesity.
Your answer is "What Causes Childhood Obesity?"
I hope this helps!