Irisin - Wikipedia, the free encyclopedia

Phys Ed: Exercise Hormone Keeps Us Healthy - NYTimes.com

Basically, it appears that exerise triggers release of the protein PGC1-alpha. This, in turn, increases expression of a the gene protein FNDC5.
That, in turn, decouples to the newly discovered hormone Irisin.
Irisin then appears to communicate with standard white adipose tissue (WAT), which is the most abundant type of fat tissue in adult humans, and begin changing them to brown adipose tissue characteristics.

Unlike WAT which is fairly inert as far as energy metabolism is concerned, BAT is much more metabolically active, burning stored energy (i.e fatty acids) to produce body heat.

BAT is quite prevalent in babies, but it gradually converts to WAT for the most part as we age. Converting it back could have some very interesting effects.

No doubt there will be all kinds of supplements and medications coming out over the years that will try and icnrease Irisin levels in people, probably with horrible side effects and a few deaths.

The bottom line is that exercise is probably the safest way to do this.