U.S. researchers reported in a recent issue of the journal Molecular Cell that exposure to cold environments helps the body increase brown fat, which burns calories to lose weight. This finding has important implications for research into the treatment of obesity and diabetes. Studies have so far found that white fat in the body is responsible for storing excess energy, while brown fat burns energy and raises body temperature. Since people usually live in a temperature-controlled environment, the need for brown fat gradually decreases, so the proportion of brown fat is high in infants and small in adults. Obese people have relatively little brown fat in their bodies. Researchers at the University of California, Berkeley, found that prolonged exposure to cold air increases the amount of Zfp516, a transcription factor that is essential for the formation of brown fat. In experiments in which the researchers turned off the gene encoding Zfp516 in mouse embryos, the mouse embryos no longer produced any brown fat. Another experiment showed that mice with higher levels of Zfp516 in their bodies spent four hours in a cold environment at 4 degrees Celsius and had an average body temperature 1 degree Celsius higher than mice with normal Zfp516 levels. In addition, mice genetically modified to have ultra-high levels of Zfp516 in their bodies gained 30% less weight than normal mice after consuming the same high-fat food for one month. This indicates that more calories were released by fat burning in the former.