The most important impediment to good diets among the poor is the price of high-quality food. Studies have shown that the price of a given number of calories of "junk food" is much lower than the price of a given number of calories of healthier food.
The poor often cannot afford or do not have access to the kinds of healthy fresh foods that nutritionists recommend that people should eat. Poor areas often lack the sorts of large grocery stores that carry many healthy choices. Even if poor people have access to such stores, they often cannot afford to pay the higher prices for the healthier foods. As the ajcn.org link below says:
... there is an inverse relation between energy density (MJ/kg) and energy cost ($/MJ), such that energy-dense foods composed of refined grains, added sugars, or fats may represent the lowest-cost option to the consumer.
In this way, economic impediments can have a great deal to do with preventing poor Americans, especially, from adopting better eating habits.
Economically: Cost. For example, eating organic is much healthier, but not everyone can afford it.
Socially: This could be something as simple as going to the cafeteria and getting a salad whereas your friends are getting pizza and you get made fun of because your eating a salad.
That is true but there are means of getting a very good balance with low cost foods. A large bag of rice and a large bag of dried beans would be very economical and supply a good balance of carbohydrates, protein and fiber. And with a llittle money spent on fresh or frozen vegetables would, of course, help. The rice and beans diet is often the bottom of the food pyramid for poor countries around the world but I don't think itis followed in more advanced countries. Poor families (that can't afford fast food) here normally buy white processed flour or processed corn meal to make bread, corn bread , and biscuits but then need meat to obtain protein with the meal. I know that it is nearly impossible for people in large cities, but for those outside the city it is easy to grow greens and roots. Collard greens, spinach, lettuce, mustard greens, radishes, carrots, and turnip greens are very easy to grow.