Why are affluent people healthier?

Marion Nestle, in her blog entry, writes about this question, which has often intrigued me. A student, who is quite big framed, was once talking about his younger days when they did not have money and his mother was relying on government assistance to take care of the family that included four children. So, this student remarked that eating up all that unhealthy food that was cheap was the reason for his large size. When Taco Bell has 79-cent items, and when an apple is more expensive than that, even a third-grader can figure out that people without money will choose that cheaper and unhealthy food.

Speaking of Taco Bell, I liked this observation in Sarah Hepola's piece on cheap and fast foods during this Great Rececssion:

There is something unsettling about the audaciously punctuated "Why Pay More!" Taco Bell value menu. I don't mean health concerns -- though those are aplenty -- but the confounding question of how a restaurant could possibly profit selling nachos at 79 cents. The nachos come covered in refried beans and goopy fluorescent orange cheese drizzled with red sauce, a wan imitation of Tex-Mex that made me weep for my years spent in Austin, Texas, but still … 79 cents! Even for recession prices, that feels low. The 89 cent Cheesy Double Beef Burrito, meanwhile, was so hefty I could practically bench-press it. It was crammed with the chain's signature chili-cheese artery-clogging mix.

Anyway, Nestle writes:

Adam Drewnowski and his colleagues at the University of Washington have been doing a series of papers on the cost of food per calorie. The latest is a research brief answering the question, "Can low-income Americans afford a healthy diet?" Not really, they say. Federal food assistance assumes that low-income people spend 30 percent of their income on food, but that assumption was based on figures from an era when housing, transportation, and health care costs were much less.

As Drewnowski has shown repeatedly, healthier foods cost more, and sometimes a lot more, when you look at them on a per-calorie basis.