Moderately Carbohydrate-restricted Diet to Treat NAFLD in Adolescents

For this study, the investigators will use the low glycemic, moderately carbohydrate-restricted diet that the investigators have previously shown is associated with depletion of hepatic lipid content, and improvement in insulin resistance in adolescents with NAFLD. This diet has a macronutrient composition of approximately 25% energy from carbohydrate, 20% energy from protein, and 55% energy from fat. No food group is excluded in this diet prescription; however, the diet emphasizes low-glycemic sources of carbohydrate, and includes mainly whole foods (vegetables, fruits, whole grains) with minimal highly processed grain products and added sugar. Protein foods will include meat, poultry, fish, eggs, and whey protein supplements if necessary. Fat-containing foods will include olive, coconut, and nut oils; butter; tree nuts and nut butters; cheese; cream; coconut milk; avocados; and the fat found in meat. A number of full-fat dairy products will be included.

The fat-restricted, control diet will consist of approximately 60% carbohydrate, 20% protein, 20% fat. Participants will be given low-fat foods, whole-grain foods, fruits, and vegetables. The meal plans will minimize cholesterol, high-fat foods, high-cholesterol foods, processed starches, and added sugar, and will provide \<2300 mg/day sodium. Saturated fat will be limited to 10% of total fat intake, and all dairy products will be fat-free (or low fat).