OCD, Obesity, and Dark Comets

<p>Dr Chris Smith and the Naked Scientist team present the latest science news, analysis and breakthroughs.</p><p>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?</p><p>Plus, an in-depth look at why some people have obsessive-compulsive disorder, and how we can help them.</p>