Brown fat is a specialized tissue in mammals that is used to generate heat (thermogenesis). While white fat is associated with increased body mass, brown fat is associated with a lower body mass index (BMI) and consumes large amounts of energy. Researchers have long been intrigued by the idea of brown fat transplant as a therapeutic tool to combat obesity. In this issue of the Journal of Clinical Investigation, researchers led by Laurie Goodyear at the Joslin Diabetes Center in Boston, performed brown fat transplants in mice to determine if this intervention could treat obesity. Using mice fed either a normal diet or a high-fat diet, Goodyear and colleagues demonstrated that brown fat transplants significantly decreased body weight and improved insulin sensitivity and glucose metabolism. Additionally, the transplanted brown fat secreted hormones, including IL-6, which mediated metabolic effects throughout the body. This study establishes brown fat as an important regulator of metabolism and suggests that this tissue could be an important therapeutic target in the treatment of obesity-related diseases.