The purpose of this study is to determine the effects of a low carbohydrate diet vs a low fat diet on improvement in aminotransferases, hepatic fat infiltration, markers of inflammation, insulin resistance, and body composition in obese adolescents with non-alcoholic fatty liver disease (NAFLD).

NAFLD is the most common form of liver disease in children in the United States. Currently, there is no treatment for NAFLD. In adults, weight loss through caloric restriction is commonly recommended to improve fatty liver. Weight loss is particularly difficult for children to achieve and significant caloric restriction may not be a prudent recommendation in developing children and adolescents. Because of this difficulty with weight loss in children, many children go on to develop cirrhosis and eventually undergo liver transplant. Data on the effectiveness of diet to reverse fatty liver and prevent progression to cirrhosis in children is urgently needed. To date, no studies have been done examining how changes in diet composition without intentional caloric restriction influences NAFLD in children. Data from previous studies in adults support the hypothesis that consumption of lower-CHO, higher-fat food sources rich in high-quality proteins and essential fatty acids has beneficial effects on metabolic health in adults without restricting calories. This study aims to test the hypothesis that a low CHO higher- fat diet will induce rapid reversal of fatty liver while also depleting of total and abdominal adiposity, preserving lean mass, and reducing inflammation in adolescents with obesity and NAFLD.

Inclusion Criteria:

• Overweight/obese (BMI over the 85th percentile) male and female adolescents (age range 10-17) with elevated serum aminotransferase levels, diffusely echogenic liver via ultrasound suggestive of fatty liver, and/or prior diagnosis of NAFLD. Participant eligibility will depend on the ability of one parent to attend the initial diet instruction and individual counseling sessions with the registered dietitian during week 2, 4 and 6 of the diet intervention.

Exclusion Criteria:

• Presence of hepatic virus infections (HCV RNA-polymerase chain reaction negative; hepatitis A, B, C, D, E, and G; cytomegalovirus; and Epstein-Barr virus), alcohol consumption, history of parenteral nutrition, and use of drugs known to induce steatosis (for example, valproate, amiodarone, or prednisone) or to affect body weight and carbohydrate metabolism. Autoimmune liver disease, metabolic liver disease, and Wilson's disease will be ruled out by the participants physician prior to enrollment in the study.