Weight Loss Theories
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.
But the scientists, who report their findings in the journal Cell Metabolism, caution that it is too soon for couch potatoes to be celebrating.
'To produce the desired effects, we would need to create a drug that blocks 2-AG production in the brain, something we're not yet able to do,' said Prof Piomelli. 'So don't cancel that gym membership just yet. But as you hit the treadmill, think about the added health benefits if you could train your brain to make fewer endocannabinoids.'
A second study published in Cell Metabolism showed that giving mice an extra copy of an anti-cancer gene produced similar effects.
Animals with the extra Pten gene were resistant to cancer and also produced more of the hyperactive brown fat that prevents weight gain.
The mice lived longer than usual and were less prone to insulin resistance, a precursor to diabetes.
'Tumour suppressers are actually genes that have been used by evolution to protect us from all kinds of abnormalities,' said lead scientist Dr Manuel Serrano, from the Spanish National Cancer Research Centre.
'This tumour suppresser protects against metabolic damage associated with ageing by turning on brown fat.'