We aimed at evaluating whether the addition of low-dose metformin to dietary treatment could be an effective approach in nondiabetic patients with nonalcoholic fatty liver disease (NAFLD). We carried out a 6-month prospective study in a series of overweight or obese patients with ultrasonographic diagnosis of hepatic steatosis. In total, 50 patients were enrolled and randomized into two groups: the first group (n=25) was given metformin (1 g per day) plus dietary treatment and the second group (n=25) was given dietary treatment alone. At the end of the study, the proportion of patients with echographic evidence of fatty liver was reduced in both the metformin (P<0.0001) and the diet group (P=0.029). Moreover, patient body mass index and waist circumference significantly decreased in both groups (P<0.001). Fasting glucose, insulin resistance (evaluated as homeostasis model assessment of insulin resistance (HOMA-IR)) and serum adiponectin decreased in both groups, although these changes reached statistical significance only in the metformin group. In this group, HOMA-IR decreased from 3.3+/-1.6 to 2.4+/-1.2 (P=0.003), whereas it decreased from 3.2+/-1.6 to 2.8+/-1.1 (not significant, NS) in the diet group. Similarly, the proportion of patients with impaired fasting glucose declined from 35 to 5% (P=0.04) in the metformin and from 32 to 12% (NS) in the diet group. At baseline, approximately 40% of patients in both groups met the diagnostic criteria of metabolic syndrome. This proportion decreased to 20% in the metformin group (P=0.008) and to 32% in the diet group (NS). In our 6-month prospective study, both low-dose metformin and dietary treatment alone ameliorated liver steatosis and metabolic derangements in patients with NAFLD. However, metformin was more effective than dietary treatment alone in normalizing several metabolic parameters in these patients.
