If living healthy was a class, the vast majority of us would be flunking, a study published recently in the journal Mayo Clinic Proceedings has found.

Just 2.7 percent of Americans have a “healthy lifestyle,” which researchers defined as hitting all four benchmarks of good health. They are: not smoking; getting regular, moderate exercise; eating a diet rich in vegetables and whole grains and low in saturated fat, and maintaining a low body fat.

For women, low body fat is under 30 percent; for men, it’s under 20 percent. The exercise benchmark requires at least 150 minutes a week of moderate exercise.

The study was conducted by researchers from Oregon State University and the University of Mississippi. Their findings echo results from other similar studies.

It seems the toughest target to hit was maintaining low body fat. The percentage of Americans who eat a healthy diet, exercise regularly and don’t smoke is 13 percent, the study found.

In addition, some groups of people fared better than others at meeting certain benchmarks. Older people were less active and had higher body fat than younger people in the study. But they were less likely to smoke and had healthier diets.

Also, women were more likely to be nonsmokers and eat healthier than men. But men tended to exercise more than women.

Of course, a main goal in cultivating healthy habits is to prevent diseases. To that end, the researchers found that having more healthy lifestyle characteristics was associated with better cholesterol, blood sugar and blood pressure numbers.

“To Your Health” offers quick doses of health news several times a week.