Participants meeting study entry criteria are randomized with equal probability to one of two study groups: (1) Lifestyle modification or (2) Vertical Sleeve Gastrectomy (VSG) with Iifestyle modification, followed for 12 months. The primary goal for the trial is to determine if the investigators can recruit, randomize, and retain participants to perform invasive and non-invasive measurements of NASH and fibrosis, deliver lifestyle modification and demonstrate the safety of VSG. The investigators wish to also understand which of these two interventions is more effective in achieving, 12 months after entry into the trial, a reduction in NAS composed of the non-weighted scores: (1) steatosis 0-3 (2) Inflammation 0-3 and (3) ballooning 0-2. Secondary goals include comparing the two treatment groups for changes in other measured outcomes including MRI assessments of intrahepatic triglyceride and liver elasticity and serum markers. As a pilot study, a sample size of 20 in each group should offer significant information as to the difference in NAS score reduction between to two groups and achieve adequate power to distinguish clinically significant changes in the primary and secondary outcome measures. These data support the overarching objective i.e. to provide evidence that a larger, longer-term clinical outcomes trial is feasible. A goal is for a longer term follow up for 5 years to assess the durability of treatment effects and treatment differences.