The 5:2 diet, also written as 5/2 diet, is a fad diet which involves severe calorie restriction for two non-consecutive days a week and normal eating the other five days, which originated and became popular in the UK, and spread in Europe and to the USA. It is a form of intermittent 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.
The diet specifies a low calorie consumption (sometimes described as "fasting") for two days a week, which should not be consecutive, but allows normal eating for the other five days. Men may eat 600 calories on fasting days, and women 500. A typical fasting day may include a breakfast of 300 calories, such as two scrambled eggs with ham, water, green tea, or black coffee, and a lunch or dinner of grilled fish or meat with vegetables, amounting to 300 calories. The daily 500 or 600 calorie limit requires small portions.