Scientists are working on an anti-obesity pill that could reduce the fat stored by overweight people by almost a half in a week.
Tests on mice have shown that the drug could decrease body weight by a quarter and their fat content by 42 per cent after seven days.
After a month, the weight of the mice had been reduced by 28 per cent and their fat mass by 63 per cent.
But experts warned that it could take a decade for the potential wonder drug to be developed for use by patients.
The researchers, whose findings are published online in Nature Chemical Biology, say further research is needed before the drug is tested on humans.
But they say the results point to a new approach for the treatment of obesity and adult-onset diabetes.
The drug is an artificial hormone that regulates glucose metabolism.
Previous studies have found this substance can suppress appetite or lead to weight loss by increasing the body's calorie usage.
Dr Richard DiMarchi and colleagues at Indiana University in the U.S. created the synthetic hormone and carried out the trials on mice.
He said: 'Obesity and its associated consequences, including adult-onset diabetes, remain a primary health and economic threat for modern societies.'
At the moment surgical interventions such as gastric bypass remain the only therapeutic options with the potential for a cure.
Dr DiMarchi said acute glucagon administration reduces food intake in animals and in humans, and may also promote weight loss.
He added: 'Pharmacological treatment of obesity using single agents has limited efficacy or presents risk for serious adverse effects.
'No single agent has proven to be capable of reducing body weight more than 5 to 10 per cent in the obese population.
'Combination therapies using multiple drugs simultaneously may represent the preferred pharmaceutical approach to treat obesity, and there is ample precedent for combination therapy in treatment of chronic diseases.
'Here we present results that prove the principle that single molecules can be designed that are capable of simultaneously activating more than one mechanism to safely normalise body weight.'
Last night, he said it would be ten years before the drug is available and tests needed to be completed on humans.
Cambridge University professor of clinical biochemistry Stephen O'Rahilly said: 'It is important that these are demonstrated to be effective and safe in animal models before going forward with trials in humans.'
He added: 'Many promising drugs fall down when tried in humans either because they don't work sufficiently well or because of side effects.
'It is far too early to tell whether this molecule will be one of the exceptions and become a safe and effective treatment for obesity in humans.'
But he concluded: 'I hold out considerable hope for the discovery of safe and effective anti-obesity therapies.'
Professor O'Rahilly said that patients being treated with the drug could take one pill a day, or an injection.