Muscle-like fat?

All fat is not not created equal: In the past couple years researchers have come to realize that there's good fat and bad fat, and a study in this week's __Nature__ points to a biological reason for this difference. White fat, the main type of fat in the body, develops from fat precursor cells and stores excess energy. Brown fat, however, burns energy rather than storing it, and the new findings suggest it originates from muscle precursor cells. That means that "brown fat is one gene away from