Here's the hard truth: Although hours of steady-state cardio is great for keeping you healthy and strengthening your heart, it’s not so great at turning up your metabolism to really torch fat. For that, you need to mix resistance exercises with high-intensity interval training—but the morbidly obese can’t just blast out the WOD "Murph" followed by a deadlift workout.

So maybe it's not surprising, then, that obesity researchers have spent years trying to find out a way to get the body to burn more fat without having to sweat. And on that front, scientists from The Scripps Research Institute in California may have stumbled upon the key to making our bodies turn on the fat-burning process without a punishing workout. It just comes from a bizarre source.

Their discovery? By turning on and off the gene pathways that connect serotonin with fat-burning in the brains of roundworms (which have most of the same signaling molecules as humans), researchers identified a hormone that stokes fat metabolism in the gut, they announced in a study published in Nature Communications.

In a first, scientists were able to observe how high serotonin levels caused a hormone to be secreted from neurons in the brain. That hormone then travels through the circulatory system to the gastrointestinal system to specifically trigger the burning of fat—without being tied to food intake. And get this: Increasing levels of the hormone didn’t cause any observable side effects, they found.

The finding could spur a whole new way to approach the obesity epidemic and create an easy and safe way to start burning fat. Sure, it might sound like a cheat code to those among us who bust their asses trying to shave off the last 10 pounds—but for people who can't just jump into an intense workout, it could be a literal life-saver.

And for those of you who are just holding on to a little extra fat and don’t want to wait for a quick fix, try out our quick and simple HIIT workouts that’ll torch those pesky few last pounds right off.