A 48-year-old man comes to the clinic for a routine check-up. He is concerned about his health because his father was diagnosed with type 2 diabetes mellitus at age 55. His body mass index is 31 kg/m2, and he has no symptoms of diabetes. His fasting plasma glucose is 98 mg/dL, hemoglobin A1c is 5.4%, and lipid panel is within normal limits. Which of the following interventions is the most appropriate primary prevention strategy to reduce his risk of developing type 2 diabetes mellitus?