Not all Fat is Created Equal

Ever wondered why it sometimes seems that thin, fit people don’t have to watch what they eat as much and are better able to keep exercising?  This month Harvard & Dana Farber researchers report on a newly discovered hormone, Irisin, that may play a role in this seemingly unfair phenomenon.  Irisin, created when people exercise, seems to turn white fat cells into brown fat cells. White fat?  Brown fat?  What difference does it make–fat is fat, right? Actually no, not all fat is created equal.

White fat just stores calories, whereas brown fat actually burns calories.  We used to think that only babies had brown fat. It was thought that they used it to help keep themselves warm until they were old enough to move around and generate their own heat, and then-no longer needing the brown fat’s heat-the brown fat was replaced by white fat.  In 2009 we learned that some adults still seem to have some brown fat, but we didn’t know how or why.  This new study seems to have revealed one possible mechanism.  In brief, exercising muscles release a hormone called PGC1-alpha which in turn leads to the creation of Irisin.  Irisin then travels to white fat and seems to signal the white fat to become brown.

Now these guys aren’t the only reasons fit people are more toned than sedentary individuals, but the study does demonstrate that the more you exercise, the more of these hormones you release, and the more brown fat you develop – ergo, burning calories for you and increasing your metabolism!

You can read more in this NY Times article.