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Doctor Isolates Exercise Hormone; Tells People To Keep Exercising

What if your New Year's resolution to get more exercise could be fulfilled — by taking a pill? That's the far-flung idea suddenly brought much closer to reality by the discovery of a hormone called irisin, which is produced by the human body in response to exercise.

Irisin may hold some of exercise's key benefits that relate to obesity and Type 2 diabetes, researchers say.

WBUR's CommonHealth blog has the story, which came out today thanks to a study in the journal Nature. CommonHealth's Carey Goldberg spoke to the study's senior author, Dr. Bruce Spiegelman, who stresses that the researchers' intent was not to give people another reason to be lazy.

"The last thing in the world we're trying to do is substitute for diet and exercise," he tells Goldberg.

But Spiegelman, who works at the Harvard Medical School and the Dana-Farber Cancer Institute, says there are plenty of people out there who simply cannot perform some activities related to exercise. And whether that's because of paralysis or illness, they might someday benefit from the discovery of irisin.

The hormone's name comes from the Greek goddess Iris, whose mythic role was to carry messages between gods and humans.

And like a message telling your body, "Hey, don't be so fat," the hormone encourages what Spiegelman calls " the 'browning' of white fat — turning on a thermogenic program in some white fat."

Brown fat is seen as the most useful, and least harmful, type of fat — while white fat merely sits there, storing potential energy, your body's brown fat actually burns calories. And recent studies have found that some people simply have more of it than others.

Because it's a polypeptide naturally produced by the body, a trial of irisin on human test subjects for irisin injections might only be a few years away, Goldberg writes.

For now, Spiegelman is excited to learn more about the hormone.

"I think people have been thinking for a long time that exercise has benefits that go well beyond the muscle," he tells Goldberg. "It affects your heart, your blood vessels, it's very anti-diabetic. So to find a polypeptide that embodies some of that is very cool."

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Bill Chappell is a writer and editor on the News Desk in the heart of NPR's newsroom in Washington, D.C.