The trillions of bacteria that live in the gut — helping digest foods, making some vitamins, making amino acids — may help determine if a person is fat or thin. The evidence is from a novel experiment involving mice and humans that is part of a growing fascination with gut bacteria and their role in health and diseases like irritable bowel syndrome and Crohn’s disease. Jeffrey S. Flier, dean of the faculty of medicine at Harvard University, is quoted.
