Tune Your Engine - the science of health and fitness

Gretchen Reynolds has a whole list of reasons why our sedentary lifestyle is killing us, and she has the science to back it up. For more than a decade, she has written about the science of health and fitness for a weekly column in the New York Times. Now she's gleaned the best bits of wisdom into her new book, "The First 20 minutes: Surprising Science Reveals How We Can Exercise Better, train smarter and live longer".