There are all types of data-driven people out there. But for Larry Smarr, gathering as much data about his body, figuring out what it means, and applying it to improve his health has become an obsession. Smarr spent 25 years as an astrophysicist and now directs the California Institute for Telecommunications and Information Technology, so he knows a little bit about data-driven analysis. Aside from gathering data using gadgets such as a FitBit, Smarr routinely has his blood and stool analyzed for certain biochemicals. It may seem excessive, but Smarr's "quantified health" fixation led him to drop over 20 pounds and, more importantly, helped his doctors make a startling discovery.