Michael Mosley runs an experiment to test whether an extra hour a week in nature improves your physical and mental health. Alain Gregoire investigates a mysterious illness that can transform a child’s personality overnight. Zoe Williams discovers the hidden body fat that can make us thin. Giles Yeo investigates whether trendy plant-based milks are any healthier than dairy. And Guddi Singh witnesses pioneering cancer surgery – using an intelligent knife that can detect tumours.