I posted this over in Living Maintenance but thought it would be of interest here, too.
Did anyone read the cover story of this week's New York Times Magazine? It's about "microbesity," which apparently is the theory that the microbes in our gut, or exposure to certain viruses, may play a role in why some of us gain and hold onto fat more easily than other people. The article notes that genes and behavior are still important contributors to obesity but if the research pans out, they'll add the microflora in our gut as a third contributor. I haven't finished the article yet. I highly recommend it if you can get your hands on it - it's fascinating.