Corresponding author: CS Mantzoros, MD, D. Sc., Division of Endocrinology, RN 325, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215, USA Abbreviations: BMI, Body mass index; C/EBPa, CCAAT/enhancer-binding protein a; PPAR γ, peroxisome proliferator activating receptor γ; NIDDM, non-insulin dependent diabetes mellitus; PCOS, polycystic ovary syndrome; cAMP, cyclic adenosine monophosphate; JAK, Janus kinase; STAT, signal transducer and activator of transcription; CNS, central nervous system; NPY, neuropeptide Y; CSF, cerebrospinal fluid; UCP 2 (or 3), uncoupling protein 2 (or 3).