Last week the New York Times published an article on two new devices in development, both of which target fat without internal intervention.  The first, the Zeltiq, uses an externally placed cooling device that selectively freezes the fat in a process know as cryolipolysis.  The second, Zerona, uses low level laser energy applied to the skin that heats fat cells subcutaneously causing them to lyse. Both companies claim that there is no damage to the skin and that only fat cells are targeted.  The devices have not yet been approved by the FDA for safety and efficacy and the article implies that patients are having mixed results. While I am enthusiasticallly in support of non-surgical options, my personal experience has led me to be somewhat cautious in the introduction of similar devices in my practice. For example, I use SlimLipo for laser lipolysis. A fiber is passed beneath the skin and a 924 nm laser selectively "melts" the fat. When we first started using SlimLipo we would measure the internal temperatures of the treated area and the temperature of the skin above the area being treated.  We were very surprised to find that there was a not only a large difference in the internal and external temeperatures, but also they did not appear to be correlated in any way. Typically, the internal temperature was much hotter then the external temperature.  We concluded that the external temperature is NOT indicative of what is happening under the skin.  Therefore, my own clinical experience leads me to be cautious of devices that are treating deeper structures without a means of monitoring them simultaneously. Thus, although these are both very interesting technologies and may, in the future, prove to clinically and aesthetically efficacious, I will reserve my judgement on Zeltiq and Zerona until many more patients have been treated in IRB studies and more data and clinical follow-up becomes available.