Exercise does more than just tone muscle and burn calories in the moment: New research shows that a hormone released during exercise actually helps the body shed fat and keep it off.
The hormone, called irisin, has been shown to play a role in transforming energy-storing white fat cells into energy-burning brown fat cells—a process scientists call “browning.” Now, University of Florida scientists say that irisin helps inhibit the formation of new fatty tissue, as well.
These findings highlight a new and additional benefit of physical activity, said co-author Li-Jun Yang, MD, a professor of hematopathology in the University of Florida College of Medicine, in a press release, because irisin levels are believed to surge when the heart and other muscles are exerted. (In addition to exercise, studies show that shivering can trigger irisin production, as well.)
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To examine the effect of irisin on human fat tissue, the researchers collected fat cells donated by 28 women who’d had breast reduction surgery. In their lab, they exposed some of the samples to the hormone and watched for changes in cell activation and gene expression.
As predicted, they found a nearly fivefold increase in activity among cells that contained a fat-burning protein known as UCP1. “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,” Dr. Yang said.
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But they made another discovery, as well: After 18 days, the fat tissue samples that were exposed to irisin had a 20 to 60 percent reduction of mature fat cells, compared to a control group. This suggests that irisin actually hinders the process that turns undifferentiated stem cells into fat cells, the authors wrote, and pushes them toward becoming bone-forming cells instead.
The study, published recently in the American Journal of Physiology—Endocrinology and Metabolism, is believed to be the first of its kind to investigate how irisin affects human fat cells. Previous research on animals has suggested that it can improve heart function, boost calcium levels in the body, and reduce plaque buildup in arteries. Next, Dr. Yang and her colleagues hope to study the hormone’s effect on dangerous abdominal fat.
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Findings about irisin’s role in regulating fat cells shed some light on a complex issue that scientists still don’t fully understand: how exercise helps people not only slim down, but also stay slim.
“Irisin can do a lot of things,” said Dr. Yang. “This is another piece of evidence about the mechanisms that prevent fat buildup and promote the development of strong bones when you exercise.”
It’s possible that irisin’s benefits could be used to develop weight-loss medications, Dr. Yang said, or even treatments or preventatives for diabetes and osteoporosis. But that likely won’t happen anytime soon; more studies are needed, and it can take years for a new pharmaceutical to be conceived, tested, and approved for sale.
For now, her message is simple: “Instead of waiting for a miracle drug, you can help yourself by changing your lifestyle,” she said. “Exercise produces more irisin, which has many beneficial effects including fat reduction, stronger bones and better cardiovascular health.”