A natural cannabis-like chemical in the brain may hold the key to keeping couch potatoes slim, early research suggests.
Scientists in the US found that blocking the compound allowed mice to gorge on high fat food and take little exercise without putting on weight or becoming unhealthy.
The genetically modified animals produced limited amounts of the endocannabinoid 2-AG, a chemical related to the active ingredient in cannabis.
All mammalian brains, including those of humans, contain 2-AG, which is believed to control neural circuits involved in metabolism.
"We discovered that these mice were resistant to obesity because they burned fat calories much more efficiently than normal mice do," said study leader Professor Daniele Piomelli, from the University of California at Irvine.
"We had known that endocannabinoids play a critical role in cell energy regulation, but this is the first time we found a target where this occurs."
The mice stayed slim because they developed a hyperactive form of "brown fat" - a special type of fat that generates heat and keeps animals warm.
Not only did they not gain weight when fed a high-fat diet, but they failed to develop any of the expected signs of metabolic syndrome. This is a combination of problems such as obesity and high blood pressure which increase the risk of heart disease and diabetes...