This study will establish the impact of WLS on NAFLD in adolescents. Currently, it is assumed that adolescents with NAFLD diagnosed at the time of WLS have universal resolution of their disease with appropriate weight loss, and no further evaluation is conducted. Our group has shown that up to 40% of adolescents who undergo WLS have persistently abnormal aminotransferase levels, suggesting that many may have persistent NASH and are at risk of progressive liver disease. The study will elucidate the history of NAFLD following WLS. Such data have not been previously published and will represent a significant contribution to this field.