It’s correct, but the use of the passive voice is awkward.

“Overall, more and more people are eating fast food.”

“Overall, the consumption of fast food is increasing.”

@gailcalled thank you :))

@gailcalled Two of the statements that you offer say very different things, and must depend on the data shown on the graph:

“Overall, more and more people are eating fast food.”—> Here, the number of people eating fast food is increasing.

“Overall, the consumption of fast food is increasing.”—> Here, the quantity of fast food being eaten is increasing.

@kiki__ What are the axes on your graph?

Without qualifiers, your sentence is, “Fast food is eaten.”
Expand that into something meaningful and re-ad your qualifiers as needed.

When you start a sentence that makes a comparison from one thing or condition to another, you have to at least mention both conditions. So although the sentence is grammatically correct as it stands*, as a topic sentence to a paragraph or essay it doesn’t make sense; it doesn’t work unless the comparison is made within the sentence. The rest of the paragraph, indeed, the rest of the essay, can help to complete and prove the argument, but the full statement of comparison has to be made.

Overall, more and more fast food is eaten…
... than slow food
... than at any other time in our history
... than used motor oil
... than we would care to admit
... than you would believe

*As @gailcalled noted, the passive voice is just not a good one for this sentence. Food doesn’t eat itself, so it makes sense to at least refer to who (or what) is eating the food.

For all those haters of the passive voice – and I realize that lately you are legion – everything depends on what was measured. If the thing that was measured was the quantity of food, then the passive voice is likely the best choice.

@dappled_leaves – YES! Finally – someone who gets it!

From The Science of Scientific Writing, which is full of very excellent advice:

“The information that begins a sentence establishes for the reader a perspective for viewing the sentence as a unit: Readers expect a unit of discourse to be a story about whoever shows up first. “Bees disperse pollen” and “Pollen is dispersed by bees” are two different but equally respectable sentences about the same facts. The first tells us something about bees; the second tells us something about pollen. The passivity of the second sentence does not by itself impair its quality; in fact, “Pollen is dispersed by bees” is the superior sentence if it appears in a paragraph that in-tends to tell us a continuing story about pollen. Pollen’s story at that moment is a passive one.”

This is not just a question of style. Science writing is first and foremost about conveying information. The writing needs to serve that, regardless of popular trends.