[Originally published at Outsideonline.com, September 3, 2015]

On July 27, the media team at the University of Southampton, in the UK, announced results from a new study concerning a molecule researchers had dubbed Compound 14. When fed to obese mice, it triggered a startling metabolic reaction: In just seven days the rodents shed five percent of their body weight. Even more miraculous, the otherwise healthy mice thinned down while continuing to gorge on a high-fat, high-carb diet—the rodent-equivalent of ice cream and pizza—and all without doing a single bout of exercise. 

The study, published in the Journal of Chemistry & Biology, called Compound 14 an “exercise mimetic,” a phrase Ali Tavossoli now laments. “We never actually said this is exercise in a pill,” says Tavossoli, a professor of chemical biology at the University of Southampton and the study’s principal scientist. In fact, the experiment was intended to explore potential therapies for metabolic disorders, diabetes, obesity, and muscular dystrophy, a disease that makes normal exercise impossible because it damages muscle tissue.

But merely suggesting that a substance could simulate exercise was enough to spark hysteria. “It all snowballed,” Tavossoli says. “I lost count of all the people I spoke to.” The Washington Post called. So did ABC News and Esquire. Then Shape magazine, which followed up with an online article, preposterously headlined “An Exercise Pill May Soon Exist for Gym-Haters.”

Let’s be clear: There is no such thing as a workout pill, now or ever. Compound 14 and similar molecules, including AICAR and GW1516 (see Faster, Higher, Squeakier, Outside, February 2011), dupe cells into thinking they’ve run out of adenosine triphosphate (ATP), their primary fuel. With ATP depleted, cells demand glucose, which is derived from burning fat. A secondary benefit—and what makes these compounds so attractive for treating diabetes—is boosting glucose tolerance. “But this is only what happens in mice,” Tavossoli points out. “We have no idea what this does in humans.”

But more importantly, these compounds are not even remotely equivalent to doing actual physical activity, “the benefits of which are huge for just about everything,” says Ron Evans, a biology professor at the Salk Institute who pioneered AICAR and GW1516 research. Exercise can prevent heart disease, stroke, cancer, and arthritis. It will make you buff, reduce stress, bolster your immune system, boost brainpower, strengthen bones, lower cholesterol, improve sleep, and supercharge your sex life. A pill that can do all this? Pipe dream. Now go to the gym.