This is a question no doubt many people are asking themselves around this time of year, when fad diets and gym memberships are at their peak. In this programme, Dr Xand van Tulleken and dietician Hala El-Shafie help six people go on the most hyped and written about diets on the market to see which works best. In tonight's episode, we meet Stefanie and Jade from Harrow who have 10 days to slim down before the launch of their clothing label. There is also advice for fast food junkies Matt from Redditch and Robb from the Wirral who try to battle the bulge before a university reunion in six weeks' time. We also follow the progress of Vicki and Kerry from Chesterfield, who want to get fighting fit for a mud race in four months.