The most appropriate management is weight loss. This patient has nonalcoholic fatty liver disease (NAFLD), and weight loss should be recommended. NAFLD is the most common cause of abnormal liver test results in the United States. Approximately 30% of the U.S. population has NAFLD, some of whom have normal liver enzyme levels. Most patients with NAFLD have insulin resistance associated with obesity, hypertriglyceridemia, and/or type 2 diabetes mellitus. Approximately 20% of patients with NAFLD have nonalcoholic steatohepatitis (NASH), which is characterized by hepatic steatosis accompanied by inflammation and often fibrosis. Although NASH requires a liver biopsy for accurate diagnosis, a presumptive diagnosis can be made in a patient with mild abnormalities of aminotransferase levels, risk factors for NAFLD (such as diabetes, obesity, and hyperlipidemia), and imaging features consistent with hepatic steatosis. This patient's liver biopsy is consistent with steatohepatitis, and given his risk factors of obesity and diabetes mellitus, NAFLD is the most likely diagnosis.

Patients with NASH who have bariatric surgery and lose weight have improvement in hepatic histology, and bariatric surgery can be considered if conservative attempts at weight loss fail.

Patients with NAFLD may have abnormal iron tests, especially serum ferritin. The absence of iron on this patient's liver biopsy excludes significant iron overload, and therefore phlebotomy is unnecessary.

Patients with NASH and cirrhosis are at significant risk for hepatocellular carcinoma, and surveillance with imaging should be performed every 6 months; however, surveillance is not necessary in the absence of cirrhosis.