This is an investigator-initiated study being conducted in equal numbers at two sites, UC San Diego and Emory University. The purpose of this study is to understand the potential of a low sugar diet for the treatment of nonalcoholic fatty liver disease (NAFLD) in children. Forty boys with NAFLD will be randomly assigned to either an intervention group or a habitual diet control group. The intervention will be a low sugar diet for a period of 8 weeks. The effect of this dietary change will be assessed using advanced MRI testing to measure liver fat