2. Group B- Obese Adolescents a. Inclusion criteria: This group will consist of obese adolescents, between the ages of 12-18 years and Tanner stage 3-5 for pubertal development. They must have: a BMI above or equal to 95th for age, but not greater than 40 kg/m2 . They must have a normal glucose tolerance, in other words subjects with undiagnosed impaired glucose tolerance or diabetes will not be considered for the study. To test them for diabetes or impaired glucose tolerance they will undergo a 2-hour Glucose tolerance test (2hr-GTT). The ADA criteria will be used for the diagnosis of diabetes and/or impaired glucose tolerance (fasting plasma glucose < 110 mg/dl and a 2 hour postprandial blood glucose < 140 mg/dl). They must have and normal liver function tests and not taking any medications. The subjects will undergo DXA scan for estimation of total lean and fat body mass. The fat mass should be more than or equal to 30% to be considered obese. The subjects in this group will be matched for age (plus minus 1year), Tanner stage (plus minus 1) and body fat mass (plus minus 5%) to the Type 2 diabetes adolescents?. Menstruating females must have a negative urine pregnancy test for inclusion. 3. Group C- T2DM Adolescents a. Inclusion criteria The study group will consist of adolescents with T2DM, between the ages of 12-18 years, Tanner stage 3-5 for pubertal development, BMI above or equal to 85th for age (but less than 40 kg/m2) and HbA1c less than 8.5%. They must have T2DM diagnosed for at least 2years, treated with diet , oral hypoglycemic agents and or insulin. If on medications they need to be on a stable dose of insulin and / or oral hypoglycemic agent over the last 2 months. The subjects must be otherwise healthy except for hypothyroidism stable on treatment. Menstruating females must have a negative urine pregnancy test for inclusion. -