A team of researchers at the Pennsylvania State University College of Medicine have uncovered a gene that allows mice to eat to their heart's content without getting fat, according to a report by Nature.
The missing gene in this case codes for an enzyme needed to chemically digest some amino acids — the building blocks of proteins. This results in the build-up of an amino acid called leucine, which in turn tricks cells into making new, unnecessary proteins and then destroying them. This pointless cycle burns up excess calories so the mice stay trim, regardless of the extra food they munch.
As for the effects of the gene on mice:
[Christopher Lynch of Pennsylvania State] says the genetically modified mice "seemed more hungry than the other mice" and ate more, relative to their body weight. But even when they were put on a high-fat diet, which makes normal mice obese, these super-slim rodents stayed lean, carrying about half the body fat of their cage-mates. Their body temperature was increased slightly as all the extra food they craved was burnt off.
On a normal diet, the modified mice seemed healthy, weighed about 10% less than normal mice, and had a lower risk of developing diabetes.
Similar effects could reportedly be achieved in humans by developing a drug to block the enzyme that breaks down leucine. "In theory, people on such a drug could eat a normal diet and still shed pounds, although what the side effects might be is unknown," Nature says.