Here’s some incentive to stick with that resolution to exercise more often. Researches in Boston at Dana-Farber have made it into Nature with a new finding on another aspect of why exercise helps us live longer and feel better. Part of the answer it turns out is that exercise stimulates production of a hormone now dubbed "irisin," and it helps to stimulate "good fat" instead of "bad fat." The short story is below; the ScienceDaily summary includes a link to the full article.
"There has been a feeling in the field that exercise ‘talks to’ various tissues in the body," said Spiegelman, a professor of cell biology at Harvard Medical School. "But the question has been, how?"
According to the report, the irisin hormone has direct and "powerful effects" on adipose, or fatty, tissue — subcutaneous deposits of white fat that store excess calories and which contribute to obesity.
When irisin levels rise through exercise — or, in this study, when irisin was injected into mice — the hormone switches on genes that convert white fat into "good" brown fat. This is beneficial because brown fat burns off more excess calories than does exercise alone.
Only a small amount of brown fat is found in adults, but infants have more — an evolutionary echo of how mammals keep themselves warm while hibernating. In the wake of findings by Spiegelman and others, there has been a surge of interest in the therapeutic possibilities of increasing brown fat in adults.
Along with stimulating brown fat development, irisin was shown to improve glucose tolerance, a key measure of metabolic health, in mice fed a high-fat diet.
The discovery won’t allow people will be able to skip the gym and build muscles by taking irisin supplements, Spiegelman cautioned, because the hormone doesn’t appear to make muscles stronger. Experiments showed that irisin levels increase as a result of repeated bouts of prolonged exercise, but not during short-term muscle activity.
The Dana-Farber team identified irisin in a search for genes and proteins regulated by a master metabolic regulator, called PGC1-alpha, that is turned on by exercise. Spiegelman’s group had discovered PGC1-alpha in previous research."