There is no question that people living in poverty face unique challenges that can lead to poor diets. Low-income Americans often cannot afford high-quality, nutritious food, but that alone is not the reason financial insecurity often leads to unhealthy eating.

Many low-income Americans also tend to live in areas where grocery stores are few and far between, and where healthy food options are limited. Poor Americans also tend to have less free time as a result of the need to work multiple jobs or irregular shifts, leaving them with less time to shop at the store or prepare nutritious meals. Poor Americans are less likely to have access to a car or other transportation needed to get to a store.

The U.S. Department of Agriculture measures the share of residents who live on low incomes and also lack access to nearby grocery stores and from that data derives the food insecurity rate. Food insecurity measures the share of households who report inconsistent access to adequate food. This could be caused by the scarcity of nearby stores — low access to food, and it can also be the result of poverty.

In some U.S. counties, over 20% of households suffer from food insecurity and more than 40% of residents are both low income and have low food access. As both factors can lead to poor diets, 24/7 Wall St. created an index based on the share of residents who are both low income and have low access to food, and the percentage of households that face food insecurity in a given month.

Click here to see the places where poverty leads to bad diets
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Three of the most food-insecure counties on this list, Apache and Navajo in Arizona and San Juan County in Utah, are each partially within the Navajo Nation, the most populous American Indian reservation in the nation, as well as the largest geographically, spanning four states. In Apache County, and in Navajo nation in general, the health crisis related to poor nutrition and poverty has been well documented. As part of a 2015 in-depth report on the region’s health crisis, Al Jazeera noted that there were just 10 grocery stores serving the entire Navajo Nation, an area with roughly 300,000 residents that is about the size of the state of South Carolina.

Residents in those two Arizona counties suffer from the same health problems that the other poor counties on this list do. Those include high obesity rates and other problems an area with roughly 300,000 residents (the same as Pittsburgh) and about the size of the state of South Carolina associated with poor diets, such as diabetes. In Apache, Navajo, and San Juan counties, for example, residents report feeling unhealthy more than five days a month.. Likely in part as a result of their food insecurity, these counties also rank as among the least healthy counties in America.