Insulin resistance (IR) modifies the anti-viral effects of interferon (IFN) therapy in patients with chronic hepatitis C (CHC). This prospective study evaluated whether lifestyle interventions improve the anti-viral response to treatment with pegylated (PEG)-IFN plus ribavirin (RBV) in patients with CHC. The study cohort consisted of 60 patients chronically infected with a high viral load of hepatitis C virus genotype 1b and a homeostasis model assessment of IR (HOMA-IR) value above 2. The patients were divided into two groups, an intervention group (n=26) and a control group (n=34). The patients in the intervention group were prescribed diet and exercise treatment for 3-6 months to reduce their body weight by ≥5% before starting treatment with PEG-IFN plus RBV. Diet and exercise significantly reduced the HOMA-IR values in the intervention group, from 3.4 to 2.5 (p=0.0009), especially among the 15 patients who achieved a body weight reduction of ≥5%. The viral disappearance rate at 12 weeks was significantly higher in the intervention group among the patients with a ≥5% weight reduction than in the control group (53.3% vs. 23.5%, p=0.01). However, the sustained viral response (SVR) rates were similar. Improvements in IR achieved through weight reduction via lifestyle interventions may enhance the early viral response to PEG-IFN plus RBV in patients with CHC. However, this intervention program has no effect on the SVR rate.