The mice were eating their usual chow and exercising normally, but they were getting fat anyway. The reason: researchers had deleted a gene that acts in the brain and controls how quickly calories are burned. Even though they were consuming exactly the same number of calories as lean mice, they were gaining weight. Joseph Majzoub, the Thomas Morgan Rotch Professor of Pediatrics at HMS and chief of endocrinology at Boston Children’s Hospital, is the lead author of the study.
