What your diet needs is a little dirt.
It sounds like the beginning of an corny old joke: What do you get when you swap the gut bacteria of a fat mouse and a thin mouse? However, the answer provides a tantalizing clue to solving one of the most dire public health challenges of our time: the obesity epidemic. In a number of studies, scientists have manipulated the intestinal microflora in mice that are obese (A) and lean (B). What they have found is when A gets B's gut bacteria, it becomes a skinny mouse and the opposite is true as well.