Scientists say they have found a way to turn body fat into a better type of fat that burns off calories and weight. The US Johns Hopkins team made the【C1】______in rats but believe the same could be done in humans, offering the hope of a new way to treat obesity. 【C2】______the expression of a protein linked to【C3】______not only reduced the animals" calorie intake and weight, but also【C4】______their fat composition. Brown fat is【C5】______in babies, which they use as a【C6】______source to generate body heat,【C7】______calories at the same time. But as we age our brown fat largely【C8】______and gets replaced by "bad" white fat, which【C9】______sits as a spare tyre around the waist. "We will need a lot more work to tease this out, but it could offer a(n)【C10】______way to develop new treatments for obesity", an expert said. Experts have【C11】______that stimulating the body to make more brown fat【C12】______white fat could be a helpful way to control weight and【C13】______obesity and its related health problems. Various teams have been searching for a way to do this, and Dr Sheng Bi and colleagues at the Johns Hopkins University School of Medicine believe they may have cracked it. They designed an experiment to see【C14】______suppressing an appetite-stimulating protein called NPY would decrease body weight in rats. When they silenced NPY in the brains of the rats they found their appetite and food【C15】______decreased. Even when the rats were fed a very【C16】______, high-fat diet they still managed to keep more weight【C17】______than rats who had fully functioning NPY. The scientists then checked the fat【C18】______of the rats and found an interesting change had occurred. In the rats with silenced NPY expression, some of the bad white fat had been replaced with good brown fat. The researchers are【C19】______that it may be possible to achieve the same effect in people by injecting brown fat stem cells【C20】______the skin to burn white fat and stimulate weight loss.