Here's what i know about dead fat cells: fat necrosis is sometimes an unwanted result of surgery (especially reconstruction). The area becomes hot & red & hard - sometimes it shrinks but sometimes you can also end up with a hard scar or lump in that spot (which might or might not go away). If its caused by loss of circulation, the tissue death can progress to gangrene.

I would be pretty cautious because of the potential for scarring. Also, how do they make sure they don't accidentally "freeze" the wrong tissue - like skin or blood vessels? How is it regulated?