A food desert is a neighborhood that is both low-income and far from a supermarket or large grocery store. The most widely used definition comes from the USDA, which measures food access at the census-tract level: in urban areas, a tract qualifies when at least 500 people or 33 percent of the population live more than 1 mile from the nearest supermarket. In rural areas, that threshold jumps to 10 miles.
How the USDA Defines a Food Desert
The USDA doesn’t use a single cutoff. Its Food Access Research Atlas applies three distance thresholds, each capturing a different degree of limited access:
- Half-mile / 10-mile measure: Urban residents more than half a mile from a supermarket, or rural residents more than 10 miles away.
- 1-mile / 10-mile measure: Urban residents more than 1 mile away, rural residents more than 10 miles. This is the most commonly cited definition.
- 1-mile / 20-mile measure: Uses a stricter 20-mile rural threshold to flag the most isolated communities.
In every case, the tract must also be low-income: either a poverty rate of 20 percent or higher, or a median family income at or below 80 percent of the state or metro area median. A neighborhood that’s far from a grocery store but affluent doesn’t count, because higher-income residents generally have cars, delivery options, or the flexibility to shop elsewhere.
Why Distance Alone Doesn’t Tell the Full Story
Living a mile from a supermarket sounds manageable until you factor in what’s actually available nearby. In many food deserts, the closest options are convenience stores and gas stations, where prices run significantly higher. USDA data shows that milk costs about 5 percent more at a convenience store than at a grocery store, cereal costs 25 percent more, and bread about 10 percent more. For a family already stretched thin, those markups add up fast, especially on staples purchased week after week.
Transportation compounds the problem. Without a car, a one-mile trip with bags of groceries becomes a real barrier, particularly for elderly residents, people with disabilities, or parents with small children. Public transit in many of these neighborhoods is limited or adds significant time to what should be a simple errand.
Food Deserts vs. Food Swamps
Researchers increasingly distinguish between food deserts and a related concept called food swamps. A food desert describes a lack of healthy food options. A food swamp describes an area where fast food restaurants, convenience stores, and other sources of calorie-dense, nutrient-poor food vastly outnumber grocery stores and supermarkets.
The difference matters because many neighborhoods technically have food nearby, just not the right kind. A study in the International Journal of Environmental Research and Public Health found that food swamps predict obesity rates better than food deserts do. When researchers controlled for the ratio of unhealthy to healthy food outlets, the effect of distance to a supermarket shrank considerably. In other words, being surrounded by fast food may be more damaging than simply being far from a grocery store.
Health Consequences of Limited Food Access
People living with food insecurity, a condition that overlaps heavily with food desert residence, face measurably higher rates of chronic disease. Among low-income adults surveyed in a large national health study, 22.4 percent of those in food-insecure households had hypertension, compared with 18.6 percent of those in food-secure households. After adjusting for other factors, food-insecure adults had a 21 percent higher risk of high blood pressure.
Diabetes shows an even sharper divide. Clinical evidence of diabetes appeared in 10.2 percent of food-insecure adults versus 7.4 percent of food-secure adults. Among those experiencing the most severe food insecurity, the diabetes rate climbed to 15.9 percent, more than double the rate in food-secure households. Women in food-insecure households also had higher average body mass than women in food-secure homes, a pattern that did not hold for men.
These numbers reflect a straightforward reality: when the cheapest and most accessible calories come from processed snacks, sugary drinks, and fast food, diet quality drops and chronic disease risk rises.
Online Grocery Delivery as a Partial Fix
The COVID-19 pandemic accelerated one potential workaround. The USDA expanded its SNAP Online Purchasing Pilot, allowing households receiving food assistance to use their benefits at authorized online grocery retailers. This gave people in food deserts access to the same inventory as a full-size supermarket without needing a car or a nearby store.
Early research is encouraging. Adults who ordered groceries online had higher diet quality than those who relied solely on nearby stores, particularly when those local stores offered limited selection. There’s a catch, though: SNAP benefits can’t cover delivery fees or service charges, which can range from a few dollars to $10 or more per order. For households counting every dollar, that fee can be a real deterrent.
Federal Efforts to Close the Gap
The main federal program targeting food deserts is the Healthy Food Financing Initiative (HFFI), which provides grants to bring grocery stores, food co-ops, and other healthy food retailers into underserved areas. To date, HFFI has awarded over $25 million directly to 162 food retail projects. In 2024, an additional $40 million went to 16 public-private partnerships designed to create or expand local food financing programs across 20 states.
These efforts are meaningful but modest relative to the scale of the problem. Building a new grocery store takes years and requires a viable customer base to sustain it. Some communities have turned to smaller-scale solutions: mobile markets, community gardens, farm stands at transit hubs, and partnerships with existing corner stores to stock fresh produce. No single approach works everywhere, which is partly why the USDA tracks multiple distance thresholds rather than relying on a single definition.
How to Check Your Own Neighborhood
The USDA’s Food Access Research Atlas is a free, publicly available mapping tool that lets you look up any census tract in the country. You can see whether your area qualifies as low-income and low-access at each of the three distance thresholds, along with demographic data about the population affected. Community organizations, local governments, and grant applicants use this tool to identify priority areas for new food retail projects. You can access it through the USDA Economic Research Service website.