A starvation diet, also sometimes called a crash diet, is a diet that consists of less than 700 calories a day. Starvation diets can cause severe health problems and should only be used with a doctor's guidance.
Starvation diets for weight loss typically last 30 days at most, because longer fasts increase the risk of health problems. While these diets do result in short-term weight loss, most people gain the weight back once the crash diet ends. Sometimes people use them for detoxification, although there is no scientific evidence that a starvation diet effective for that purpose. Starvation diets are similar to fasts that people undergo for religious or cultural reasons, but the goals are different.