A high-fat, high-sugar diet can quickly and dramatically change the population of microbes living in the digestive tract, according to a new study of human gut bugs transplanted into mice.

Trillions of microbes live inside the human gut, and one of their functions is to process parts of foods that we can't digest on our own. Recent studies have suggested that certain populations of microbes may be associated with obesity.

via The Gut Response To What We Eat : NPR.