In patients infected with genotypes 1, 4, 5 and 6, the response rate to antiviral therapy remains suboptimal (less than one in two patients have a sustained virological response), which justifies the search for strategies optimizing the results of antiviral therapy. Some factors associated with non response have been identified. Among the modifiable factors, numerous series have shown that insulin resistance adversely impacts the rate of sustained virological response. The aim of this study is to determine whether the pharmacological correction of insulin resistance through therapy with glitazones restores higher rates of viral eradication and to determine the impact on the kinetics of viral response. Patients will be randomized to receive pioglitazone or placebo starting 4 months before initiating pegylated interferon and ribavirin and continued throughout the whole antiviral treatment period.