Evidence of brown fat activity in constitutional leanness.

Background: Brown adipose tissue (BAT) was considered essentially nonexistent in adults until recent evidence obtained using 18-fluorodeoxyglucose (18-FDG) positron emission tomography/computed tomography. It seems to play a role in whole body metabolism, but it has not been evaluated in underweight conditions, such as in young females with constitutional leanness (CL) or anorexia nervosa (AN).

Subjects And Methods: Thirty-eight subjects were evaluated from October 2011 to March 2012 : 7 CL (21.