It’s been said any medicine that replicated the health-giving benefits of exercise would be hailed as a miracle drug. Well, that day seems to be getting closer. But could we really replace a workout with a prescription, and would this really be progress?

Live longer, have better sex, increase your memory, build muscle tone, burn fat ... with supposed benefits like these, it's no wonder that the search is on for a medication that mimics what happens when we exercise.

What scientists have discovered, however, is that the body’s responses to exercise are so complex at so many levels that emulating all (or even just some) of these effects will be enormously difficult and unpredictable.

At the same time, there has been a surprising amount of progress made already. American-based journalist Nicola Twilley has been exploring the development of a so-called “exercise pill” and recently shared her fascinating findings in a brilliant article for the New Yorker.

You can hear her discuss the frontiers of synthetic exercise in this interview, and also find out what she thinks of a future where popping a pill could replace working out.

This interview comes courtesy of Radio New Zealand.

In some ways, the future is already here. Twilley came across one drug in particular, known as GW501516 (or just 516 for short), that is showing promising early results in rodents – but also in a small group of humans who have been willing to risk unknown side-effects because of the drug’s apparent effect on their fitness levels.

As she describes in her New Yorker article, two groups of mice were given an “average American” lifestyle of processed food and no exercise. What the researchers termed “Couch Potato Mouse” became lethargic, overweight and physically run-down.

What they termed “Lance Armstrong Mouse” lived under exactly the same conditions, and yet was lean, muscular, in seemingly great physical condition, and comparatively active.

The only difference was that Lance Armstrong Mouse had been given a daily dose of GW501516.

The drug was originally developed in the 1990s as a possible treatment for metabolic syndrome (the name given to a group of symptoms including obesity, high blood pressure and high blood sugar, which can be precursors to heart disease and diabetes). Due to an increased cancer risk in mice, the drug company behind the trials shelved the project in 2007 – but not before the obvious beneficial results had already been noted.

While there is clearly a long way to go, the genie is out of the bottle. A pill may not ever replicate all the effects of exercise – including the social and less tangible emotional aspects – but it might prove effective as a short-term treatment for everyone from astronauts dealing with muscle loss in zero gravity, to hospital patients or elderly people whose movement is restricted.

As Twilley points out, with physical inactivity contributing to so much chronic disease, the public health benefits of such a medication will increasingly become the focus of ethical and political debate.

Twilley herself remains sceptical. “I think once we approach this from a biochemical perspective, yes we’ll learn more about and that’s important … but we might lose something too.”

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