Donald Lloyd-Jones of Northwestern University Feinberg School of Medicine in Chicago examined risk factors for heart disease in teens and found many had high blood sugar, low physical activity and smoked.
The study, presented at an American Heart Association meeting, found U.S. teens' diets were high in sodium and sugar-sweetened beverages, but low in fruits, vegetables, fiber and lean protein, said a statement by the U.S. Health and Human Services.
"We know that we tend to gain weight as we age through adulthood, so we're already seeing that our teens are off to a very poor start," Lloyd-Jones said.
One way to improve child and teen health is to provide more opportunities for them to eat fruit and vegetables.
Sonia Kim, a researcher for the Centers and Disease Control and Prevention, found that 1-in-4 teens were eating fruit less than once a day, and 1-in-3 were eating vegetables less than once a day.
Teens should get the equivalent of four or five cups of fruits and vegetables a day -- more if they're physically active. A cup is about a medium apple or a large tomato.