Junk food is unhealthy food that is high in calories from sugar or fat, with little dietary fiber, protein, vitamins, minerals, or other important forms of nutritional value. It is also known as HFSS food (high in fat, salt and sugar). Precise definitions vary by purpose and over time. Some high-protein foods, like meat prepared with saturated fat, may be considered junk food. Fast food and fast food restaurants are often equated with junk food, although fast foods cannot be categorically described as junk food. Most junk food is highly processed food.