It may be possible to re-engineer fat cells to burn calories, suggests new University of California, San Francisco research. A protein called PRDM16, which is found in both humans and mice, appears to make fat cells burn metabolically active. Although most diet drugs are aimed at blocking the absorption of calories, new compounds aimed at activating PRDM16 may help people burn more calories. Metabolically active brown fat, once thought to be present only in infants to help protect the body from cold, is now known to be present in small amounts throughout life. Brown fat helps create heat in the body by burning fatty acids, which heats the blood, thus warming the body. Researchers have noticed that PPAR-gamma ligands, a common class of drugs given to people with diabetes, increases brown fat. To understand why this happens, researchers found that PPAR-gamma stabilizes PRDM16 and makes it accumulate inside cells, converting white fat into brown fat in mice. The researchers are now looking to find ways to stabilize PRDM16 in humans to see if it will also cause white fat to become brown.