A diet pill that can help women drop a dress size in a matter of months could be on sale within two years.
In a large-scale study, overweight men and women who took lorcaserin for a year lost an average of 8 per cent of their body weight.
This equates to a stone for a 12st woman – and at least one dress size.
In one or two extreme cases in the 7,000-strong trial, dieters lost up to 40 per cent of their body weight, with most of the pounds melting away in the first few months.
Appetite was cut, waistlines shrunk and cholesterol and blood pressure were lowered, the European Congress on Obesity in Istanbul heard yesterday. Lorcaserin's Californian manufacturer, Arena, now plans to apply for permission to sell the twice-a-day drug in Britain early next year.
That means it could be routinely used to help win the battle of the bulge by 2013.
With Britain facing the worst weight problem in Europe and just one obesity drug on the market, some doctors argue there is an urgent need for new clinical solutions.
However, despite lorcaserin's apparent effectiveness, safety concerns prompted by tests on rats have prevented it being sold in the U.S.
The authorities there have insisted that Arena carries out more research before it gains a licence.
The drug, taken before breakfast and dinner, affects the way the brain uses serotonin, a chemical that regulates appetite, making those who take it feel less hungry.
Common side-effects in the trial were headaches, dizziness and nausea, but they tended to be temporary.
Crucially, the drug appeared to be free of the cardiac and psychiatric side-effects that have caused other obesity pills to be removed from the market in recent years.
Some have criticised the development of drugs to treat a problem which, they argue, should be addressed by healthier living.
In response, Arena's vice-president Dr Christen Anderson said: 'Diet and exercise are the cornerstone of any treatment programme but they may not be enough.
'Study after study has shown that motivation can wane and sometimes people need just a little help.
'Right now, patients have very few options. Surgery is a fairly extreme measure, so I think physicians and patients are really eager to have new tools to help battle obesity.'
It is not known how much lorcaserin will cost, but orlistat, the only diet pill currently available on prescription, costs around £1 a day.