Those living in lower-income communities and of the least education experience consistently higher rates of obesity due to the availability and affordability of calorically dense and nutritionally deficient foods resulting from the food deserts and food swamps that characterize these neighborhoods.
A food desert refers to an area in which access to supermarkets, and thus healthy, fresh, and affordable groceries is limited. Those living in food deserts often subsist off convenience store foods, and sometimes even liquor stores.
A food swamp refers to an area with a high concentration of fast food restaurants, and where unhealthy foods (high calories, fat, sugar, and sodium) are much more readily available than healthier options.
These lower income neighbors are also much more likely to associate with high rates of crime, making it dangerous for children to play outside on the streets or in playgrounds, decreasing their opportunities for informal physical activity. Compounding that problem is the fact that after school programs and recreation or little league sports are about as rare as the typical “soccer mom” in these neighborhoods. Kids have few opportunities to exercise and play, which in combination with their poor diets drives up the prevalence of obesity at alarming rates.
http://ageconsearch.umn.edu/bitstream/122142/2/02FoodDeserts.pdf
http://ije.oxfordjournals.org/content/35/1/100.short
http://communityplates.org/food-rescue-transforms-food-deserts/