Cryotherapy induces the human body's natural defenses against hypothermia, which is a mechanism that heats the body.  The mitochondria (the energy powerhouse of cells) in each individual cell ramp up a process called mitochondrial thermogenesis in an attempt to prevent the body from dropping in temperature.  This in turn has a heating effect of the entire body resulting in calorie burn.

In addition, repeated exposure to cold has been shown to increase the percentage of a special type of brown fat tissue.  This happens when the number of mitochondria in the fat tissue is increased due to the cold exposure.  This type of fat tissue was long thought to have only existed in humans during infancy, but this old dogma has been recently disproven.  

In fact, brown fat tissue has been shown to have an inverse correlation with body fat percentage.  In other words, the more browned fat tissue an individual possess the lower the body fat percentage will be.  This browning of fat tissue has been identified as a potential treatment for obesity.  Studies have shown that cold exposure has the ability to increase metabolic rate by 350%.