A 52-year-old man from rural Maharashtra presents to a health camp with complaints of polyuria and polydipsia for 3 months. He works as a farmer and has a sedentary lifestyle during off-season. His BMI is 28.5 kg/m². Fasting blood glucose is 156 mg/dL, and HbA1c is 8.2%. His father had type 2 diabetes diagnosed at age 55. What is the most significant epidemiological risk factor for diabetes in this patient?