This study will measure fat accumulation over a 12 week period in adolescents and young adults taking an AAP for the first time. MRI imaging will measure hepatic, and visceral adipose tissue at baseline and study end. An Oral Glucose Tolerance Test will measure glucose resistance and insulin sensitivity. In an exploratory fashion, investigators will also image the brain to assess for volumetric changes which may occur in association with AAP treatment and changes in metabolic indices.