From ACLU.org:
A joint report by the ACLU and New York Law School revealed that 23.5 million Americans live in "food deserts"—communities with "no access or severely limited regular access to healthy and affordable food." Over half of these people are low-income.
...One key federal effort, the National School Lunch Program, was created 65 years ago to meet the nutritional needs of low-income children, and it today it feeds lunch to some 30 million school children, either for free or at a reduced cost.
Perhaps this is one reason why many low-income people live in "food deserts." Grocery stores and restaurants can't compete with free government food.