Effect of Amino Acids on Hepatic Fat Content in Adolescents (AMINOS Study)

Inclusion Criteria - Ages 13-18, Tanner stage 4-5 - Suspected or diagnosed with NAFLD per fibroscan or liver biopsy within 6 months prior to enrollment as long as participants have not lost more than 5% of total body weight. Their MRI liver fat \>5.5% - Diagnosis of non-alcoholic fatty liver disease (NAFLD) per hepatologist - Sedentary- less than 3 hours of moderate (jogging, swimming, etc.) exercise a week - BMI equal or greater than the 85th percentile for age and gender, this is overweight and obese categories Exclusion Criteria - Use of medications known to affect insulin sensitivity: metformin, oral glucocorticoids within 10 days, atypical antipsychotics, immunosuppressant agents, HIV medications. - Currently pregnant or breastfeeding women. Development of pregnancy during the study period will necessitate withdrawal from the study - Severe illness requiring hospitalization within 60 days - Diabetes, defined as Hemoglobin A1C \> 6.4% - BMI percentile less than the 85th percentile for age and sex. Waist circumference \>200 cm - Anemia, defined as Hemoglobin \< 11 mg/dL - Diagnosed major psychiatric or developmental disorder limiting willing to sign a consent form - Implanted metal devices that are not compatible with MRI - Use of blood pressure medications - Known liver disease other than NAFLD or AST or ALT \>150 IU/L Always talk to your doctor about whether this trial is right for you.