So, you’re one of those lucky Americans keeping your weight in line. That’s great. Chalk it up to good genes or a diet without junk food. But if you aren’t getting enough exercise, maintaining a normal weight isn’t necessarily a shield against cardiovascular disease. You still have to work at it.

A recent study by researchers at the University of Florida and the University of North Carolina found that low levels of exercise can put healthy weight adults at the same risk of cardiovascular disease as those who are overweight.

The false sense of confidence engendered by a normal body-mass index, or BMI, may lull some people to go easy on their exercise regimen. Bad idea.

The study, published in the American Journal of Cardiology, found that 30 percent of normal-weight adults nonetheless have an increased risk of heart attack or stroke. Researchers say these people have higher levels of belly fat, shortness of breath when exerting themselves, unhealthy waist circumference or less than recommended levels of exercise.

Researchers say traditional thinking has been that people with a normal BMI have a low risk of heart disease. But BMI, they note, shouldn’t be the only yardstick in measuring good health.

The study is based on an analysis of data from the National Health and Nutrition Examination Survey and focused on participants ages 40 to 79 who did not have a previous diagnosis of coronary heart disease, stroke or heart attack.

Researchers note federal guidelines recommend 150 minutes of moderate intensity exercise weekly for adults. So, don’t let that dreamy BMI keep you out of the gym.

When it comes to heart health, there is no free lunch.