Getting a mix of different foods requires actual access to those foods. In areas researchers call food deserts, convenience stores and fast food outlets outnumber grocery stores, making fresh fruits and vegetables harder to find. By surveying residents about how often they eat fresh food and comparing store inventories between urban and non-urban communities, this experiment reveals how geography can limit the variety that a balanced diet demands.

Some areas have many fast food restaurants and convenience stores but few grocery stores — researchers call these areas food deserts. You visit food stores in an urban area and note what percentage of their inventory is fresh produce, then repeat the same steps in a non-urban area. Comparing the two communities shows how store access shapes what people can actually eat.