Nonalcoholic fatty liver disease (NAFLD) is systematically associated with insulin resistance and the metabolic syndrome, where behavior therapy remains the primary treatment, simultaneously addressing all the clinical and biochemical defects. However, very few studies have tested the effectiveness of intensive behavior therapy in NAFLD, aimed at lifestyle modifications to produce stable weight loss by reduced calorie intake and increased physical activity. Searching the literature for studies testing weight loss and lifestyle modifications for the treatment of NAFLD, only 14 reports were traced where the entry assessment satisfied well-defined criteria. The final effectiveness was based on hard histological outcomes in 5 cases. All but 1 were pilot, uncontrolled studies or limited case series, and in general the details of treatment were scanty. In only 3 cases treatment was carried out along the guidelines of behavior treatment to reduce excess nutrition and increase exercise; in these cases, a remarkable effect on weight loss and an improvement in liver histology were reported. The principles of behavior therapy are presented in detail, to help physicians change their prescriptive attitude into a more empowerment-based approach. A brief section is also included on the practical aspects and public policies to be implemented at societal level to obtain the maximum effects in lifestyle changes. There is a need for multidisciplinary teams including dietitians, psychologists, and physical activity supervisors caring for patients with NAFLD. Alternatively, general practitioners and physicians working in gastrointestinal units should limit their intervention to engage patients with NAFLD before referral to specialized teams set up for the treatment of diabetes and obesity.