You're overestimating the effect of intelligence on one's food choice. You're also conflating intelligence, ability to earn, and education. Network effects and

You're overestimating the effect of intelligence on one's food choice. You're also conflating intelligence, ability to earn, and education. Network effects and marketing have a much bigger role to play here. It's very common for middle class to follow upper and upper-middle class habits once they have the means. And if it's habit forming, like fast food, it's very hard to get rid of it. Combine that with massive marketing using American dollars, and you've got a huge problem that's hard to get rid of without government intervention.