1. Group A- Lean Adolescents a. Inclusion criteria: This group will consist of 20 lean adolescents between the ages of 12-18 years, Tanner stage 3-5 for pubertal development, have a BMI less than 85th and above 20th for age and an HbA1C less than or equal to 6% (normal range is 4-6%). They should not be taking any medications. A DXA scan will be performed to estimate lean and fat body mass. The body fat mass should be less than or equal to 25 % to be included in this group (in the lean range). The subjects will be matched for age and Tanner stage to the subjects in Group B and C. Menstruating females must have a negative urine pregnancy test for inclusion.The subject must weigh more than 43 kg.