Eat junk -> Feel like crap, low energy -> Eat more junk
Not a good long term strategy. There are widely available low cost foods that can help break that loop. Rice, beans, eggs, frozen vegetables... In fact frozen vegetables are often more nutritious than non-frozen, unless you're eating close enough to picking time.
Put a bunch of effort into making good food -> Feel like crap
Seems obvious what I pick.
That's exactly the point. When you're poor, you don't have the luxury of considering a long term strategy.
That's exactly the point. You don't break out of those just by deciding one day to be rational.
Don't bend over backwards to excuse people of personal responsibility.
I agree, it's unlikely many people have literally thought through "what single food will best maximize my calorie intake?"
However, it's relatively intuitive that spending some amount of money on cereal will get you further than spending the same amount on Apples. And so they buy cereal.