Ketone bodies—molecules produced by the breakdown of fat—promote the regeneration of stem cells in the intestinal lining, according to new work from the laboratory of Ömer Yilmaz. In a study appearing in Cell, researchers found that intestinal stem cells produced unusually high levels of ketone bodies, even in the absence of a ketogenic (high-fat) diet, and that these molecules stimulate the Notch pathway to boost stem cell production. Comparisons of diets in mice suggest that ketogenic diets may help repair damage to the intestinal lining, which can occur in cancer patients receiving radiation or chemotherapy. This research was supported in part by the Koch Institute Frontier Research Program through the Kathy and Curt Marble Cancer Research Fund, the MIT Stem Cell Initiative, and The Bridge Project, a collaboration between the Koch Institute and Dana-Farber/Harvard Cancer Center.