There are several causes and effects of the popularity of fast food restaurant and fast food. The first cause is needs of modern community which have intensive activities. In a family, both husband and wife have a tendency to have jobs. Consequently, they do not have enough time to cook and the frequency of eating take out is increased. Most people work full days with a lunch break of limited time, thus practically they need fast food for lunch.Secondly, efforts of fast food restaurant companies to improve their products and services are also the cause of their popularity. Improving products include food quality in diverse taste. For example, KFC in Thailand offers a special taste which may not be found in other countries. Restaurants also provide good services such as quick service, convenience place even fun and entertain. Some restaurants also provide free delivery services which consumers can just call to order. Serving food in many kinds of package can make consumers choose quickly by pointing to the appropriate picture and price.Besides its popularity, fast food has some effects on human health. Most fast food contains calories from refined sugar and fats. It is also high in sodium from salt and other additives which can lead to someone to eat it more and more. Consuming more calories than human needs lead to obesity, which causes some health problems such as hypertension, diabetes, heart disease and even cancer.In conclusion,the popularity of fast food restaurants is caused by lifestyle of modern people, food quality and good services. Besides its popularity, fast food has an effect on human health. Reducing frequency of fast food meal and eat more fresh vegetables and fruits may lead to reduce health risk in the future.