An obesity “master switch” has been found that makes it possible to feast on junk food without getting fat.
The discovery in mice could lead to new slimming treatments for humans within 10 years, scientists believe.
A US study found that mice lacking the IKKe gene became effectively immune to obesity.
It meant the animals could eat a super-fatty diet and still stay slim.
They were also protected against chronic inflammation, a condition known as “fatty liver”, and the first signs of diabetes.
Deleting the gene appeared to release the “brakes” on energy expenditure, generating heat.
Mice on the “junk” diet were fed a type of lard with 45% of its calories derived from fat.
Normal mice given the same unhealthy food rapidly gain weight while their metabolic rate slows down. But the “knockout” mice lacking the IKKe gene burned up the extra calories instead of storing them as fat.
For comparison, a group of “control” mice were fed a standard diet in which fat accounted for just 4.5% of calories.
“The knockout mice are not exercising any more than the control mice used in the study,” said lead researcher Dr Alan Saltiel, from the University of Michigan, Ann Arbor.
“They're just burning more energy. And in the process, they're generating a little heat as well.”