Less than half of U.S. adolescents are living heart-healthy lives, and lack of exercise and poor diets could be creating a new generation of heart-disease patients.

But the latest survey confirms the fear that the current generation of teens could be at greater risk of heart disease than their parents if they don't change their eating and exercise behaviors.

Christina Shay, an epidemiologist at the University of Oklahoma Health Sciences Center, led a study of 4,673 teens ages 12 years old to 19 years old who participated in the National Health and Nutrition Examination Surveys between 2005 and '10. The sample is demographically representative of the 33.2 million adolescents in the U.S.

As in previous studies, Shay and her colleagues found that these teens were a sedentary group that ate unhealthy foods. More than 80% ate what the researchers rated as a poor diet — high in fast foods and processed foods as well as sugar-sweetened drinks, and low in fruits and vegetables and whole-grain products.

Less than 1% of the teens were eating an ideal healthy diet. As for physical activity, 44% of the girls and 67% of boys exercised an hour or more per day, with 13% of boys and 23% of girls not physically active at all.

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