Hormone Find Could Yield 'Exercise Pill' Irisin sends messages from muscle cells to fat cells By Rob Quinn, Newser Staff Posted Jan 13, 2012 3:06 AM CST 8 comments Comments Researchers found that exercise programs significantly boosted volunteers' levels of irisin. (AP Photo/Mark Lennihan) (Newser) – In research that may alarm gym owners, scientists have found a hormone responsible for many of exercise's health benefits. The newly discovered hormone—named "irisin" after the Greek messenger goddess Iris—turns ordinary white fat cells into energy-burning brown fat, and helps ward off diabetes by improving glucose tolerance, Time reports. Researchers found that the body produces irisin in response to exercise, and the hormone helps muscle cells "talk" to the body's fat cells. Scientists believe that the protein could yield "exercise in pill form," offering new treatments for diabetes and obesity in people unable to exercise. Irisin does not, however, build muscle or strengthen bones. “We’re not trying to replace diet and exercise,” the lead researcher says. “That’s still important." The catch—as usual—is that irisin injections have so far only been tested on mice, but the hormone is identical in mice and humans, and researchers hope to begin clinical trials relatively quickly.