"Pretty much all signs of heart disease went when mice were given this drug," the unit's deputy director Sean McGee told AAP.
Their enlarged hearts - a common symptom of obesity - returned to normal size. They also became more efficient at pumping blood, and their blood sugar levels fell.
And tests showed their muscles responded in the same way they would have if they'd been exercising.
The result was fitter mice that could run for longer in treadmill tests, and burned more fat when they did.
They didn't, however, lose any weight.
"The mice actually tended to eat a little bit more which isn't really surprising because we know that exercise alone is not that effective at making you lose weight, which is more associated with dietary changes," Associate Professor McGee says.
"This drug is not a weight-loss panacea. It doesn't do much for vanity."
But it holds great promise for people suffering with serious, weight-related health problems.
"At the moment there's no effective treatment for the heart disease you see associated with obesity, and heart disease and diabetes are still the biggest killers of those patients," McGee says.
The next step will be to produce a more potent form of the drug, and then aim for human trials in about four to five years' time.
McGee says his phone has been running hot over the discovery, including calls from pharmaceutical companies. The discovery was reported in the international journal, Cell Reports, today.
- AAP
