Scientists have developed an “exercise in a pill”, a drug that lets mice experience the benefits of intense exercise without ever lifting a paw. The researchers say this has the potential to be life-changing for those unable to exercise, such as the elderly, obese, or those with physical disabilities.

After taking this drug for eight weeks, the mice were able to run on a treadmill for 70 percent longer – over 100 minutes more – than mice not on the drug. The discovery was featured in a study published in the journal Cell Metabolism this week.

"It's well known that people can improve their aerobic endurance through training," senior author Ronald Evans, a Howard Hughes Medical Institute investigator, said in a statement. "The question for us was: how does endurance work? And if we really understand the science, can we replace training with a drug?"

The drug activates a gene pathway (PPARD) that prevents sugar from being an energy source during exercise and makes the muscles burn fat instead. Previously, scientists genetically engineered mice to have this gene permanently activated. Just like this drug, it made them extremely good long-distance runners that were resistant to weight gain and highly responsive to insulin.

"Exercise activates PPARD, but we're showing that you can do the same thing without mechanical training," said lead author Weiwei Fan, a Salk research associate. "It means you can improve endurance to the equivalent level as someone in training, without all of the physical effort."

Weirdly, the muscles of mice did not show the changes that typically accompany aerobic fitness, such as additional mitochondria, more blood vessels, and more muscle fibers that burn fat rather than sugar. That means that these changes are not the only thing driving exercise endurance.

The drug, known as GW501516 and GW1516, is currently sold on the black market as an illegal performance enhancing drug. Needless to say, this study was carried out on mice, so the exact effects on humans aren't as known yet. However, the researchers suggest that this drug could be used to treat people with obesity or type 2 diabetes. Alternatively, it could be used to improve patients' fitness after surgery or those unable to move.

However, that’s all a very long way off. For now, we suggest hitting the gym and cutting down on the fast food.