Don’t smoke.

Although your best plan to live longer is to adopt all four lifestyle factors, if you had to choose one, the researchers say, this is it.

Smoking affects coronary arteries and lungs, and smokers also have increased rates of cancer and risk of stroke.

Maintain a healthy weight.

The healthiest people in the study maintained a body mass index (BMI)—a ratio of height to weight that measures body mass—of less than 25.

To find out your BMI, try using a free BMI calculator. To reach (and maintain) a healthy BMI, get busy on lifestyle changes 3 and 4.

Get up and move.

Aim for about 30 minutes of activity a day most days of the week. Try breaking it into three 10-minute bouts of activity per day—a 10-minute walk in the morning, another at lunch and a stroll after dinner.

Make healthy food choices.

The study found that the healthiest people followed a Mediterranean-style diet. That means a diet rich in fresh fruits and vegetables, tree nuts with healthy oils, fish (and less red meats), whole-grain carbs and olive oil for cooking.