Dr Zoe Williams investigates whether people can boost their metabolism, Michael asks whether people should be worried about air pollution, and Dr Saleyha Ahsan meets survivors of eating disorders to try to identify the signs and symptoms. Gabriel Weston visits the Netherlands to find out about a new treatment for eczema, and Dr Chris van Tulleken reveals what kind of weights people should be lifting at the gym.

The team conducted a survey of 2,000 people to find out what mental health questions the public most wanted answered. The top question was how to beat stress: Michael Mosley runs a big experiment to test mindfulness, yoga and gardening to find out which is the best stress-buster. New presenter, psychiatrist Dr Alain Gregoire, tests how lack of sleep affects our mental health and uncovers some unexpected symptoms. Dr Zoe Williams finds out why laughing can be as good as exercise for improving mood. Surgeon Gabriel Weston investigates the radical new treatment that could cure schizophrenia in many patients and holds new hope for more common mental illnesses like depression. And geneticist Dr Giles Yeo finds out if you can eat your way to happiness.