When we last visited the gut bacteria lab at the University College of Cork, we learned that the strange and tiny creatures that inhabit your stomach have the power to exert a major influence on weight gain and loss. Now comes more recent research suggesting that exercise has the power to exert a major influence on gut bacteria. Gretchen Reynolds reports in the New York Times on a study that looked at the diversity of bacteria in the gut microbiomes of three groups of men: one made up of professional rugby players, one made up of men who exercised moderately, and one group of sedentary and generally overweight people. As Reynolds writes: “The rugby players had considerably more diversity in the make-up of their gut microbiomes, meaning that their intestinal tracts hosted a greater variety of germs than did those of the other men, especially the men in the group with the highest B.M.I.” Wait, there’s more. Even though the rugby players did much more and more extreme exercise than the other groups, they had less evidence of inflammation in their muscles. Curiously, the greatest amount of inflammation was found in the group that exercised least. The researchers caution that they really don’t know if it’s the rugby players’ exercise or their (heavy on protein) diet that results in a greater diversity of gut bacteria. Yes, you guessed it: more research is needed.