The Amazing Link Between Exercise and the Fat-Burning Hormone Irisin
If you’ve been having a hard time sticking to your exercise program in the first few weeks of 2018, the latest findings from a team of researchers at the University of Florida College of Medicine should inspire you. What they found recently was that moderate aerobic endurance activity – such as going out for a brief run – stimulated the body’s production of a hormone known as irisin, which has critical fat-burning properties.
Back in 2012, a team of researchers at Harvard Medical School first wrote up their findings of the link between exercise and irisin in the journal Nature. In fact, that’s when the hormone FNDC5 first became known as “irisin." and the first time that researchers hypothesised about the fat-burning properties.  The Harvard researchers viewed irisin as a chemical messenger capable of being activated during exercise and came up with the inspired idea of naming the hormone after a Greek goddess.
First and most importantly, irisin acts as a messenger hormone that activates specific genes within your body and the production of a protein that transforms “bad” white adipose or fat cells into “good” brown fat cells. The white fat cells store calories, while the brown fat cells help to burn calories, even after you’ve stopped exercising. So Irisin is re-wiring your body to burn fat . It also improves metabolism by increasing energy expenditure and has an impact on insulin resistance. 
And the good news doesn’t stop there. Irisin blocks the formation of fatty tissue in the future. In a lab setting, the University of Florida researchers found some genuinely extraordinary results: the production of irisin could reduce the number of fat cells formed by anywhere from 20 to 60 percent!  That means that you’re helping your body set up a barrier against fat formation in the future.
The one caveat, though, is that not every form of exercise may induce the production of irisin. The researchers specifically noted that the physical activity had to be “moderate” in nature and that it had to involve “aerobic endurance” movement. Thus, any form of exercise that doesn’t get your heart rate up to certain levels may not be as effective. Any form of anaerobic exercise, also, might not work as effectively to trigger the “exercise hormone.”
Irisin then acts as a “messenger,” telling the various parts of your body how to respond. It essentially informs your body that you need to start burning fat instead of storing fat and that you need to cut down on your production of adipose tissue in the future.
What’s becoming clear is that exercise is about more than just building stronger muscles and bones, or about improving overall cardiovascular health. Those are all vital, of course. But physical activity could be playing a more significant role in triggering biological and biochemical mechanisms within your body. Every time you exercise, your body is ramping up its production of irisin, which is then distributed throughout your body. 
Irisin could be a hormone therapeutic for human metabolic disease and other lifestyle diseases that are improved with exercise. Irisin is one to watch.
Research:  Rodríguez A, et al., "Crosstalk between adipokines and myokines in fat browning.", Acta Physiol (Oxf)., Feb 2017  Bostrum P, et al., “A PGC1-α-dependent myokine that drives brown-fat-like development of white fat and thermogenesis.”, Nature (2012)  Yang Z., Chen X., Chen Y. & Zhao Q., "Decreased irisin secretion contributes to muscle insulin resistance in high-fat diet mice.", Int J Clin Exp Pathol 8, (2015)  Yang Z., Chen X., Chen Y. & Zhao Q., "PGC-1 mediates the regulation of metformin in muscle irisin expression and function.", Am J Transl Res 7, 1850–1859 (2015)