OCD, Obesity, and Dark Comets

Dr Chris Smith and the Naked Scientist team present the latest science news, analysis and breakthroughs.Including a chat with Dr Chris Van Tulleken about why he's tackling obesity in his Christmas lectures this year, and what are the dark comets that space scientists are now documenting?Plus, an in-depth look at why some people have obsessive-compulsive disorder, and how we can help them.