The Exercise Hormone Irisin Exists, Says Science, So Here's Everything We Know About It So Far

Big news, everyone: Scientists are saying that new research has proven the existence of irisin, the "exercise hormone" (named after Greek messenger goddess Iris). Irisin's existence has been hotly debated in recent years, but if these new findings are right, we could potentially be looking at a major breakthrough in the world of physical health and fitness. Some claim that irisin will not only help us get in shape easier, but might also make us smarter and slow down the aging process. But what exactly is irisin, and how does it work? Let's review what we know so far about our someday-maybe-BFF flighty hormone goddess.

Back in 2002, scientists discovered FNDC5 — a protein that, nearly a decade later, turned out to be the precursor to irisin, a hormone that seemed to increase in mice during exercise. As soon as even the hint of irisin existing in humans burst onto the radar of science, controversy exploded. Dozens of studies were undertaken. Some claimed to prove that irisin was in humans, while others claimed to prove the opposite.

Finally, Harvard scientists studying irisin announced a breakthrough last week, saying that "These data unequivocally demonstrate that human irisin exists, circulates, and is regulated by exercise." They were able to make this bold statement after a new peptide-binding technique helped them isolate where the irisin appears under a mass spectrometer (yes, think the Major Mass Spec in Abby's lab on NCIS). The results led The Scientist to publish an article titled "Irisin Redeemed."

So we know now that irisin does exist, and that we make more of it by exercising. But what does the hormone do once our heart rate goes up and it starts pumping through our blood? Apparently, it turns white fat into brown fat. And since brown fat is better for us, since it burns energy instead of just storing it ... well, you can see how that might be a good thing for our physical health. By triggering the switch from white fat to brown fat, irisin increases our metabolism. Studies also showed that it has other fancy skills, like triggering the growth of new neurons and activating genes involved in learning and memory. And of course, the other big kicker: Increased irisin levels were shown to be associated with longer telomeres — which, while not translating directly to fewer wrinkles, does mean that our cells stay younger and healthier. This in turn makes us less prone to basically every kind of age-related illness, including cancer, heart disease, and dementia.

Unfortunately, the history of controversy probably means it will be a while before the entire scientific community gets on board and starts figuring out how to harness the power of irisin to make us all feel even more fabulous than we already do. In the meantime, we can start today by increasing our own levels of irisin with a jog around the neighborhood or a new exercise routine.

Images: condesign/pixabay, kirinqueen/Flickr; Giphy