Researchers at the Joslin Diabetes Center have demonstrated that adult humans still have a type of “good” fat previously believed to be present only in babies and children. Unlike white fat, which stores energy and comprises most body fat, this good fat, called brown fat, is active in burning calories and using energy. The finding, reported in the April 9th issue of The New England Journal of Medicine, could pave the way for new treatments both for obesity and type 2 diabetes.
Scientists had thought that brown fat only existed in humans during childhood and was mostly gone by adulthood. The paper shows that brown fat not only exists in adult humans, but also for the first time, that the fat is metabolically active.
“The fact that there is active brown fat in adult humans means this is now a new and important target for the treatment of obesity and type 2 diabetes,” said C. Ronald Kahn, M.D., senior author and Head of the Joslin Section on Obesity and Hormone Action and the Mary K. Iacocca Professor of Medicine at Harvard Medical School.
Obesity is a major risk factor for type 2 diabetes. According to the researchers, the idea behind a new therapy would be to find a way to stimulate brown fat growth to both control weight and improve glucose metabolism.
“Not only did we find active brown fat in adult humans, we found important differences in the amount of brown fat based on a variety of factors such as age, glucose levels and, most importantly, level of obesity,” said lead author Aaron Cypess, M.D., Ph.D., a Research Associate and Staff Physician at Joslin.
Not surprisingly, the study found that younger patients were more likely to have larger amounts of brown fat, and the brown fat was more active during colder weather, keeping with its role of burning energy to generate heat. Brown fat was also more common in adults who were thin and had normal blood glucose levels.