Are researchers close to developing an exercise pill?

Today's booming gym business could start to go bust if scientists confirm the initial promise of two performance-enhancing, fat-melting pills that mimic the physiological benefits of exercise without all the sweat.

Results published today in the journal Cell show the drugs turn ordinary mice into trim marathon champions. There should be no shortage of volunteers ready see if they do they same in humans.

The two drugs, which go by their scientific names AICAR and GW1516, have two different target demographics: Couch potatoes might consider AICAR, which seems to build endurance and encourage fat burning through the same molecular processes that go on during real exercise. GW1516 may be more for athletes, because it boosted endurance even more but only if the mice did about 30 minutes of treadmill running a day.

Study leader Ronald Evans of the Salk Institute started by genetically engineering mice to have unusual physical endurance and a seeming inability to store fat no matter how much they ate. He then studied how the altered gene worked, and sought drugs that would do the same thing.

Evans said he thinks the drugs could have the biggest and most immediate benefit for people with muscular dystrophy, other muscle-wasting diseases, or disabilities that make exercise impossible. But the promise of exercise-in-a-pill will be seductive to everyone from the mildly flabby weekend warrior to the aspiring Olympic medalist.

Since enhancement drugs are still considered cheating in the Olympics, pro baseball, and many other competitions, Evans has already devised blood and urine tests to detect them. So in the future, elite athletes may be the only ones who still have to get sore and sweaty.