This post is in response to The “Exercise Hormone” Irisin Is NOT a Myth by Christopher Bergland
 maradon 333/Shutterstock
Source: maradon 333/Shutterstock

In the first study of its kind on fat tissue and fat cells, researchers at the University of Florida have discovered that an exercise-induced hormone, irisin (also known as FNDC5), is a fat-fighting powerhouse. The results provide a new source of motivation for exercising more or losing some weight and keeping it off.

Irisin is called the “exercise hormone” colloquially because it's released during moderate aerobic endurance activity when your cardiorespiratory system is engaged and your muscles are exerted.

The groundbreaking study shows that irisin fights fat with a one-two punch. First, irisin appears to activate genes and a protein that transform calorie-storing white fat cells into brown fat cells—which continue to burn energy after you finish exercising. Second, irisin appears to inhibit the formation of fatty tissue.

The September 2016 report was published this week in the American Journal of Physiology - Endocrinology And Metabolism. This study affirms that stimulating the production of irisin via exercise is a beneficial clinical intervention for maintaining healthy body weight and combating obesity. This research was led by Li-Jun Yang, professor of hematopathology in the UF College of Medicine’s department of pathology, immunology, and laboratory medicine.

Double Whammy: Irisin Gives Fat Cells and Adipose Tissue a One-Two Punch

For this study, Yang et al. collected fat cells from 28 patients who had undergone breast reduction surgery. After exposing the fat cells to irisin, they found a nearly fivefold increase in cells that contain a protein known as UCP1. This protein is essential for fat "burning" to occur. In a statement to University of Florida, Yang said, 

"We used human fat tissue cultures to prove that irisin has a positive effect by turning white fat into brown fat and that it increases the body's fat-burning ability. The findings about irisin's role in regulating fat cells sheds more light on how working out helps people stay slender.

Instead of waiting for a miracle drug, you can help yourself by changing your lifestyle. Exercise produces more irisin, which has many beneficial effects including fat reduction, stronger bones, and better cardiovascular health.”

Yang and her collaborators found that irisin literally suppresses fat-cell formation. When they tested fat tissue samples of an exercise group to a sedentary control group, they found that irisin reduced the number of mature fat cells by a staggering 20 to 60 percent.

The researchers believe that irisin is reducing the storage of fat in the body through a complex chain reaction that hinders a process by which undifferentiated stem cells are turned into fat cells. Irisin also appears to simultaneously promote stem cells' differentiation into bone-forming cells.

Tracing the Roots of Irisin's Discovery

In January 2012, Bruce Spiegelman, a cell biologist at Dana-Farber Cancer Institute at Harvard Medical School and colleagues first reported their revolutionary discovery of exercise-induced irisin in the journal Nature.

Spiegelman coined the term irisin, in reference to the Greek mythological goddess Iris (the messenger of the gods) after discovering the role FNDC5 played as a chemical messenger sent when muscles were activated during exercise in both mice and humans.

In 2012, Spiegelman told the Harvard Gazette, “There has been a feeling in the field that exercise 'talks to' various tissues in the body. But the question has been, how?" The study published this week by Yang helps solve the riddle proposed by Spiegelman over four years ago.

At the time of irisin's initial discovery, Spiegelman had a hunch that he and his team had pinpointed biological mechanisms that translate physical exercise into beneficial changes throughout the body. Spiegelman and colleagues have long believed that irisin is a highly promising candidate for developing novel interventions for weight loss, obesity, and diabetes—​as well as the prevention and treatment of other maladies, including cancer.

A wide range of studies since 2012 have continued to show that the “exercise hormone” irisin has many potential health benefits. As an example, in 2015, Yang and her colleagues discovered that irisin improves heart function by boosting calcium levels required for heart contractions. In June of 2016, Yang and another group of scientists found that higher levels of irisin reduced arterial plaque buildup in mice by thwarting the accumulation of inflammatory cells. This prevented atherosclerosis.

Understanding the Power of Irisin Should Motivate You to Exercise More

Approximately, two out of three U.S. adults are overweight or obese according to the National Institutes of Health (NIH). Additionally, the CDC reported in June 2016 that only 49 percent of adults 18 years of age or older meet the Physical Activity Guidelines for aerobic physical activity (150 minutes per week).

Clearly, Americans are under exercising and not producing enough irisin individually and collectively. This is a public health crisis that affects us all in one way or another. The good news is that small amounts of moderate aerobic exercise will stimulate the production of irisin. In conclusion, Yang drives home the practical aspects of her research with actionable advice: 

“Knowing that the body produces small quantities of fat-fighting irisin underscores the importance of regular exercise. Irisin can do a lot of things. This is another piece of evidence about the mechanisms that prevent fat buildup and promote the development of strong bones when you exercise."

Hopefully, these findings will inspire you to create an uptick in your daily irisin production by kickstarting an exercise routine and making a commitment to move more and sit less.

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