Michael Mosley investigates whether diet or exercise is a more effective way to keep calories in check, and Saleyha Ahsan runs an experiment to find out whether probiotic products really can improve health. Chris van Tulleken discovers whether red wine lives up to its healthy reputation, Zoe Williams looks at how sleep duration affects how much people eat, and Gabriel Weston witnesses the first operation of its kind in the UK - fitting a sternum implant made using 3D printing.