Interestingly enough, these unhealthy patterns were true across the board for Americans of all different income levels. After breaking the population down into brackets of Low income ($20-$29,999), Middle income ($50-$69,999, no word on what happened to the $30-$49,999 group, probably that disappearing middle class we keep hearing about), and High income ($70,000 plus), the percentages remained very close to the average of the population as a whole.
Moral of the story: you should be buying more fruits, veggies, and grains. Oh, but that means you'll have to actually cook something? Never mind. snag another microwave dinner, throw it in the cart, and you're good to go. That's the American way.