What is junk food? For example — are cheeseburgers and French fries junk food? What about when you make them at home, or at a fancy restaurant without artificial ingredients? Is it certain additives? If McDonalds makes a happy meal without additives, is it no longer junk food?

What does treat them like cigarettes mean? Tax them? Ban them within 15 feet of a building entrance? Put warning labels? Is giving or selling French fries to children a crime? Does this apply to food made at home?

People have tried. Any time the government tries to do anything a substantial portion of the electorate throws a childish hissy fit and tries to make out that the Bolsheviks are coming to make their fries less tasty for no good reason.

And have a real conversation around Corn syrup.

Even today, a Soda with 'real sugar', at least for me, is far more satiating for thirst or a 'quick sweet treat' than the same brand/'flavor' using corn syrup, that includes both the big chains as well as the local names.

If I drink a soda with sugar in it, I usually wind up wanting water after. If I drink something with corn syrup, I usually just want more of whatever I just had.

Unfortunately in most countries the blocker is politics, not the desire of public health officials to do anything. See the current US admin going after vaccines while declaring open season for peptides.

this is exactly right. We've got this society that readily accepts unpleasantness as what you need to do to get ahead(I'll question that but it's beside the point). People regularly accept suffering of all sorts. However, ask someone to eat a boring meal. that's a hard no. So, you've got large parts of society that won't accept that perhaps they shouldn't eat like children.