Fast food in the US is significantly more expensive than preparing your own food from basic ingredients. There may be some lower-income people who eat lots of fast food, but it's certainly not because it's the economical choice.
Learning to cook economically and edibly is a barrier to entry. And there's an ongoing higher time-cost per meal due to planning meals, getting ingredients, and (finally) cooking. So it's not suuuper surprising to me that people working 2+ jobs to cover basics end up eating a lot of fast food.
Cost is one problem. Availability is another: fresh produce takes up a lot of space, and the kinds of supermarkets that carry them don't want to move into poor neighborhoods.
Another is time: minimum wage for a 40 hour work week earns you less than $15,000 a year (in the US). So many working poor are working more than 40 hour weeks, and can't take the time to cook, even if they can afford and obtain ingredients. Fast food is cheap, available, and fast.
Sadly, no. I ended up in a tough situation in college (someone bailed on housing part way through the semester), and I cut out fast food entirely. Take for example, the ubiquitous Big Mac meal, A drink, a burger, and fries for $5.99 (plus tax). You can assemble that your self (sans fries, maybe a salad instead) for probably $3 even. You can save up to 40% buying ground beef in larger "family packs", getting super cheap store-brand bread and buns helps stretch your money a bit more. Getting vegetables in bulk packs from places like Costco can save you money, that was pretty life changing to discover. When you really look at it, there's probably $2.50 of labor built into every fast food meal that you can save by cooking for yourself.
It’s a time/energy issue more than a cost issue. General cooking ingredients are dirt cheap here. But finding time to cook while working multiple part time jobs isn’t as easy.
Cost for fresh food or even just generic ingredients in the US is crazy low. I'm in Canada but am from the US and there is a non-trivial cost difference in things like milk and veggies.
Bigger problem is that low-income folks don't have the time, the access, or the urge -- marketing aimed at low-income folks works as well as on any demographic -- so they miss out.
If you're working 49 hours a week in 2 jobs and taking the bus home, are you gonna have the time to make steel cut oats and organic quinoa with mushroom broth, or are you going to hit the easiest thing on the way home, aka a quick burger at McD's? Quinoa ain't bad, but it doesn't hit the spot a the way a burger does either.
Fast food is an expensive luxury to poor Americans who would live on generically branded large bags of frozen goods that are heated in an electric oven or microwave.
If we're talking the cheapest and worst food habits of the poorest, we're talking lots of ramen and tons of frozen foods. You can get big bags of frozen french fries for way cheaper than fast food. $3 gets you a fry at McDonalds or a 2 pound bag of frozen generic.
