How do you think people came to act this way? Why aren't we all eating our vegetables in a state built on selling vegetables?
You might wonder about why Hoosiers are unhealthy and think "those people can't resist junk food" and conclude "it's because they lack self-discipline." But you could also ask yourself "Can they even easily access healthy food easily?"1 "Why is healthy food more expensive?" "Why don't people have time to cook?" "Why is there so much junk food rather than healthy in the first place?" "Do they know how to cook healthy?"
More ideas to keep in mind
Being poor is incredibly stressful, between working multiple jobs, long commutes, children to care for, and worrying about meeting bills. That causes immense stress, which lowers willpower and makes us want to soothe ourselves, like with food.
Time. Lower wages mean less access to convenience (like owning a car to get around), meaing less time to cook or eat, hence the appeal of FAST food.
This one is crazy but - Businesses are happy to take advantage of you. The factories built to make shelf-stable food for our soldiers didn't have anything to do after the war and turned to make commercial goods. Since then they've been trying to sell us things that were as appealing as possible ("man I can't quit soda!") with as little cost involved, and then market it heavily and turn a huge profit. We have vending machines in my high school with 50 kinds of candy and maybe and apple somewhere. Pizza is a vegetable.