We hear a lot in the media about fad diets, and you may have even tried a few yourself. One of the more famous ones is the so-called 5:2 diet, also known as intermittent fasting, where the aim is to drastically cut down on calories, but only for two days a week. But does the science behind it stand up? A new review of the evidence behind intermittent fasting, published this week in the journal PNAS, suggests that it might. One of the researchers who's been putting this diet to the test in lab mice and humans is Mark Mattson, from the National Institute on Ageing in the US. Based on the animal studies and the limited short-term trials in humans, it looks like the 5:2 approach to dieting could be a good thing. One person who tried it, making a BBC Horizon documentary and writing a book about his experience, is Dr Michael Moseley. Kat Arney asked him what it's like being on the diet...