A 72-year-old woman with stable angina and hypertension is reviewed in general practice. She takes perindopril and metoprolol, and uses sublingual glyceryl trinitrate occasionally. Blood pressure is 130/78 mmHg, LDL cholesterol is 2.8 mmol/L and HbA1c is 5.7 percent. According to current Australian preventive guidelines, which additional intervention offers the greatest benefit in secondary prevention of cardiovascular disease?