The 5:2 diet, also written as 5/2 diet, is a diet which involves severe calorie restriction for two days a week and normal eating the other five days, which originated and became popular in the UK, and spread to Europe and the USA. Caloric restriction (CR), or calorie restriction, is a dietary regimen that is based on low calorie intake. "Low" can be defined relative to the subject's previous intake before intentionally restricting calories, or relative to an average person of similar body type. CR without malnutrition has been shown to work in a variety of species, among them yeast, fish, rodents and dogs to decelerate the biological aging process, resulting in longer maintenance of youthful health and an increase in both median and maximum lifespan. Intermittent fasting (IF) is a pattern of eating that alternates between periods of fasting (usually meaning consumption of water and sometimes low-calorie drinks such as black coffee) and non-fasting.
The diet is claimed to promote weight loss and to have several beneficial effects on health. According to the UK National Health Service there is limited evidence on the safety and effectiveness of the diet; they advise people considering it to consult their doctor.
source : wikipedia
