The kinds of food that people eat vary from one country to another and even within countries. In some countries, for example, the people eat much meat. In some other countries, meat is served only on special occasions. People who are vegetarians eat no meat at all. Many people like certain foods that other people find very unappetizing. The Chinese use the nests of birds called swifts to make bird's-nest soup. The birds build the nests with their saliva.

People of various cultures also prepare foods differently. In many cases, the fuel resources and cooking equipment available determine how foods are prepared. Thus, some people cook foods over an open fire. Others may use a microwave oven. Still others may eat most of their foods raw. Some people add fiery spices to their dishes. Others prefer little seasoning. Some people eat only natural, or unprocessed, foods. Others eat foods that have been highly processed.

Diets differ for a number of reasons, including (1) geographic reasons, (2) economic reasons, (3) religious reasons, and (4) customs. But differences in diet are not as great as they once were. The growth of tourism and the development of modern transportation and communication systems have led to an exchange of foods and eating habits among people throughout the world.