Aim I: A cross sectional study to evaluate baseline mitochondrial function in obese children compared to non-obese children. Determine whether children with pediatric obesity have impaired mitochondrial function based on 31P magnetic resonance spectroscopy when compared to healthy non-obese control children.Examine the relationship between mitochondrial function and insulin resistance in obese and non-obese children. Determine the impact of pubertal stage on mitochondrial function in obese and non-obese children.