An 'exercise pill' that makes the body fit without moving a muscle has been hailed by scientists following stunning test results.
The drug fools the muscles into thinking they have exercised long and hard, rapidly burning fat and boosting fitness.
The couch potato's dream, it gives the benefits of exercise without leaving the sofa.
Billed as 'exercise in a pill', it could combat ills from obesity to muscle-wasting diseases.
Even the frailty of old age could be eased by the drug's muscle-building powers, the US scientists believe.
Ronald Evans, one of the researchers and a world-leading biologist, said: ''We have exercise in a pill.'.
Professor Evans, of the Salk Institute in California, showed that the drug, which is known as AICAR, boosts fat burning and stamina in inactive mice.
'Couch-potato' animals that took AICAR for four weeks burned more calories and had less fat than untreated mice.
And when tested on a treadmill, they could run almost 50 per cent longer than untreated mice.
Effectively, the creatures had become fit without moving a muscle, a feat that Professor Evans said left him 'blown away'.
'It is tricking the muscle into "believing" it's been exercised daily,' he said.
'It's basically the couch-potato experiment and it proves you can have a pharmacological equivalent to exercise.'
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