Natural “exercise” hormone transforms fat cells

Exercise makes cells burn extra energy—that’s one way it helps control weight. It also generates a newly discovered hormone, called irisin, that transforms energy-storing white fat cells into energy-burning brown fat cells. Irisin also appears to help prevent or overcome cellular changes that lead to type 2 diabetes.

“Irisin travels throughout the body in the blood and alters fat cells,” explains Dr. Anthony Komaroff, editor in chief of the Harvard Health Letter, in the June 2012 issue. “If your goal is to lose weight, you want to increase the number of brown fat cells and decrease white fat cells.”

Fat “color” makes a difference

White adipose tissue, more commonly known as body fat, is the tissue that dimples thighs, enlarges waists and derrieres, and pads internal organs. Each white fat cell stores a large droplet of fat. Brown fat, in comparison, is chock full of energy-burning mitochondria. Its main function is to generate body heat by burning fat.

Babies are born with brown fat, but it was thought to gradually disappear. In 2009, several studies showed that adults still have brown fat cells lurking in their bodies. Earlier this year, a team led by Dr. Bruce Spiegelman, professor of cell biology and medicine at Harvard Medical School, identified irisin in mice and humans. His team also showed how irisin transforms white fat cells into brown ones, at least in mice. The same thing is likely to happen in humans, too, but that remains to be worked out.

This transformation helps the body burn more energy during exercise. The effect lingers, since brown fat cells keep burning fat even after you’ve stopped exercising. In addition, Spiegelman’s work showed that irisin also helps prevent or overcome insulin resistance, which leads to type 2 diabetes.

No need to wait

The possibility of creating a new medication based on irisin for weight loss or type 2 diabetes may have pharmaceutical companies already mapping out the long, expensive process for bringing a new drug to market. But you can make your own irisin today, for free, by exercising. And even if irisin’s effects aren’t quite as potent in humans as they are in mice, you are still getting all the other benefits that exercise has to offer.

Click here to read the full Harvard Health Letter article on irisin.


  1. Telcan

    True, but study after study has only found a behavioral link to exercise and weight loss, not a causative one, and maintaining a level of intensity necessary to burn significant calories over time is beyond most people in terms of practicality and ability.

  2. Telcan

    Exercise can be a weight loss tool. I believe the reason why exercise fails for a weight loss tool for many people is that they people sometimes overcompensate by eating a lot more.Also, exercise can burn many calories. It all depends on your intensity.

  3. Anthony

    I have always thought that
    physical execrcise + balanced diet = perfect life.

  4. Anonymous

    This article is very interesting and useful for me and I’m sure many other readers also felt this. Thank you for this good information.

  5. Sarder

    I am personally a diabetic patient. Reading this article was great add to my knowledge thanks for you valuable contribution Dr.

  6. Dan

    Time to go make some irisin! Thanks for the info.

  7. Bjorn Ulv Jensen

    Diabetes 2 is not tempting, but dieting must do the trick, exercising isn’t part of the lifestyle. Look to the swimming champion Alexander Dale Oen, his heart couldn’t take anymore. Some people exercise in order to avoid ponder too deeply. Not me. Not yet. Dieting must be enough. I would recommend dietary supplement.

  8. Shannon van der Bilt

    Thank you very much for this interesting article. I learned a lot from it!

    Shannon van der Bilt

  9. Anonymous

    So you’re saying that exercise is good for me? Groundbreaking! Hah, but all humor aside, it’s pretty awesome that there are fat cells in charge of burning other fat.

  10. Marielaina Perrone DDS

    Great article. Learn something new every day. Fascinating discovery.

    Marielaina Perrrone DDS

  11. Marksmanbeatz

    This is definetly a article i will mention to lots people especially stubborn who want to loose weight its amazing how technology has played key role in are view of diet and nutrition but back hundreds of years ago there wasn’t a epidemic of obesity so in are day in age this article is like the penicillin to the black plague of the dark ages of are day of weight issues

    Dieting will always be an issue to beat because of a re large selection of sugary and salty food we are condition to eat in america

    • The Fat Truth

      Weight issues are simply someone who consumes more calories than burns. Simple as that. Everything else is just excuses.

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