There's a slight nuance, but time isn't really the issue. "Today most people cut down on junk food" suggests most people, as a general practice, reduce the amount of junk food they consume. They've made a conscious decision to do so. "Today most people are cutting down on junk food" puts the emphasis on the process: people are reducing their junk food consumption. It's probably deliberate, but it doesn't have to be; "people are eating less meat," for example, might happen simply because they can't afford it because prices have gone up.Doesn't the second sound like it's happening exactly today?
Do you mean today, whatever day it is, and not yesterday?Doesn't the second sound like it's happening exactly today?
"Nowadays" (or "Anymore") is often used in place of "Today," and with exactly the same sense as in your sentence. It means "Things have changed in the course of time."Today most people are cutting down on junk food.