Controlled Trial of WLS vs. CLI for Severely Obese Adolescents With NASH

Inclusion Criteria: * Adolescents ages 12-19 years (range as defined by World Health Organization). * BMI ≥ 35 to 69 kg/m2 (minimum BMI per current guidelines for WLS in adolescents). An upper limit of BMI was set to avoid rare outliers in BMI. * Meet current standard of care eligibility criteria for adolescent WLS. * Liver biopsy for clinical indication to evaluate for NASH within 1 year of enrollment. Biopsy must confirm definite or borderline NASH with a minimum histological NASH Activity Score of ≥ 3. * No evidence of any other liver disease by history, screening tests or histological evaluation. * Written informed consent from parent/legal guardian and informed assent from the adolescent Exclusion Criteria: * Evidence of other chronic liver disease: autoimmune hepatitis; hepatitis B; hepatitis C; hemochromatosis; alpha-1-antitrypsin (A1AT) deficiency; Wilson disease; use of medications known to cause fatty liver for \> 2 consecutive weeks in past year (i.e. systemic glucocorticoids, tetracycline, anabolic steroids, valproic acid); alcohol intake \>10 gm/day females \& \>20 gm/day males. * Non-compensated liver disease with any of the following: hemoglobin \<10 g/dL; white blood cell count \<3,500 cells/mm3, platelet count \<130,000 cells/mm3 of blood, direct bilirubin \>1.0 mg/dL, total bilirubin \>3 mg/dL, albumin \<3.2 g/dL, international normalized ratio (INR) \>1.4 * Active psychiatric disorder that would prevent eligibility for WLS or impede adherence to CLI, including clinically significant depression (hospitalization or suicidal ideation) in past 12 months. * Any medical condition preventing eligibility for WLS including but not limited to micronutrient deficiencies (e.g. iron) refractory to medical therapy or inflammatory bowel disease. * Poorly controlled Type 2 diabetes mellitus (T2DM) defined as hemoglobin A1C (HgbA1c) \> 10%. * Initiation of high dose vitamin E (\>400 IU per day) or other medications which could alter NASH histology at any time after baseline liver biopsy or during the trial. Stable dose of vitamin E that was started 12 months or more prior to biopsy is allowed. * Weight reduction of \>5% between baseline liver biopsy and enrollment, as weight loss \>5% may change NASH severity. * Inability or failure to provide informed assent/consent * Current enrollment in another clinical trial or receipt of an investigational study drug within 6 months prior to the baseline liver biopsy * Any female who is currently nursing, planning a pregnancy, known or suspected to be pregnant, or has a positive pregnancy screen * Inability to travel to study site at intervals necessary for clinical interventions (CLI or WLS). * Prior history of WLS.