A food desert is an urban district with little or no access to foods needed to maintain a healthy diet, but often served by plenty of fast food restaurants.The concept of 'access' may be interpreted in three separate ways.'Physical access' to shops can be difficult if the shops are distant, the shopper is elderly or infirm, the area is hilly, public transport links are poor, and the consumer has no car. Also, the shop may be across a busy road, difficult to cross with children or with underpasses that some fear to use because of a crime risk. For some, such as the disabled, the inside of the shop may be hard to access physically if there are steps up, or the interior is cramped with no room for walking aids. Carrying fresh food home may also be hard for some.'Financial access' is difficult if the consumer lacks the money to buy healthy foods (generally more expensive, calorie for calorie, than less healthy sugary fatty 'junk foods') or if the shopper cannot afford the bus fare to remote shops selling fresh foods and instead uses local fast food outlets. Other forms of financial access barriers may be inability to afford storage space for food, or for the very poor, living in temporary accommodation that does not offer good cooking facilities.Thirdly, the mental attitude or food knowledge of the consumer may prevent them accessing fresh vegetables. They may lack cooking knowledge, or have the idea that eating a healthy diet isn't important.In some urban areas, grocery stores have withdrawn alongside residents that have fled to the suburbs (see urban sprawl). Low income earners and senior citizens who remain find healthy foods either unavailable or inaccessible as a result of high prices and/or unreachable locations.In rural areas local fresh food outlets have closed leaving shoppers without cars in these areas with difficult access to healthy foods, as rural bus services have also declined. Whilst the idea of 'food deserts' in the early 21st century has mainly an urban flavour, the first case studies into difficulties faced by consumers accessing healthy foods were made in rural English villages. the Womens' Institute looked at the plight of elderly car-less widows left stranded by closure of village shops and withdrawal of bus services as far back as the 1970s.The food desert phenomenon is considered a form of social exclusion.