The doctors return to do more science research on the nation's behalf in this special programme. Dr Saleyha Ahsan and the University of Oxford test whether it is really possible to bust belly fat, and skin surgeon Gabriel Weston takes a special camera on the streets to see how protective sun cream actually is. And as the warmer weather tempts more of the population to do some exercise, GP Zoe Williams makes a guest appearance to test what it's really doing for people's health. Dr Chris van Tulleken and University of Nottingham measure whether the craze for high-intensity exercise is as beneficial as the hype would suggest, whilst Michael Mosley investigates some surprising ways to get the benefits of exercise without doing any at all.