Science comes a step closer to a workout in a pill

Ever wished you could wash down that pizza, cheesecake and beer with a magic pill to make it all vanish from your waistline?

The prospect may be only a few years away, say Australian scientists doing research on a drug to simulate the effect of exercise, a move sure to excite couch potatoes the world over.

"I've loosely called it the vanity drug," said Bruce Kemp, senior research fellow at St Vincent's Institute of Medical Research in Melbourne. "A lot of pharmaceutical companies are now working on this very actively," he said.

St Vincent's and the Commonwealth Scientific and Industrial Research Organization (CSIRO) have identified and unlocked the structure of an enzyme - a protein that kicks off chemical reactions - that turns off the synthesis of fat and cholesterol.

"This enzyme is activated during exercise and it accelerates your metabolism to make up for the energy deficit in your muscle that's been created by exercise," Kemp said.

"There's been international interest in the enzyme," he said.

Scientists believe the enzyme, technically known as AMP-activated protein kinase, plays a role in regulating appetite and body weight.

But those seeking six-pack abdominals would still have to pump iron as any future pill would not tone muscles, Kemp said.

"You have to do some work. There are no miracles. (The pill) will do a number of the metabolic and gene transcription events that are caused by exercise but it doesn't do everything."

Despite Australia's reputation as a heavyweight performer in international sport, around half its adults, and a quarter of its children, are overweight or obese.