A new study has found that cardiovascular mortality rates among young adults is steadily increasing because the overall health of teenagers is worse now than at any time in U.S. history.

The study by researchers at Northwestern University Feinberg School of Medicine discovered that one in three American children and adolescents from ages 12 to 19 are overweight and have high blood sugar, 25 percent have smoked, and more than half don’t get enough exercise.

As a result of poor eating habits and a more sedentary life style, many are likely to die of heart disease between the ages of 35 to 44, according to the study presented Wednesday at the American Heart Association Scientific Sessions in Orlando, Fla. Researchers said they were surprised by the findings after reviewing the health profiles 5,547 young subjects nationwide because cardiovascular mortality rates had been decreasing.

“After four decades of declining deaths from heart disease, we are starting to lose the battle again,” said Dr. Donald Lloyd-Jones, one of the study’s lead investigators.

“We are all born with ideal cardiovascular health, but right now we are looking at the loss of that health in youth,” added Dr. Lloyd-Jones, an associate professor of preventive medicine at Feinberg. “Their future is bleak.”

Among the study’s findings:

- The eating habits of the nation’s youth aren’t just bad, they’re awful. For example, none of the study subjects' diets met the five criteria for being healthy because they were high in sodium and sugar-sweetened beverages and included hardly any fruits and vegetables. “They are eating too much pizza and not enough whole foods,” observed Dr. Lloyd-Jones.

- Thirty-five percent of boys and girls in the study were overweight or obese, which Lloyd-Jones described as a “startling” situation that only “worsens with age.”

- And the study revealed that more than 30 percent of boys and more than 40 percent of girls had elevated blood sugar, putting them at high risk for Type 2 diabetes.

Lloyd-Jones said the problems won’t be easy to fix because Americans are much more sedentary, get less sleep and have developed poor eating habits. “It’s a cultural phenomenon, and the many pressures on our health are moving in a bad direction,” he said. “This is a big societal problem we must address.”