According to researchers in the U.S. as many as one in three American teens are physically unfit and already have many of the risk factors for heart disease.

The news regarding adults is not any better as the researchers at the Feinberg School of Medicine at Northwestern University in Chicago say that 14% of adults under the age of 50 are also fundamentally unfit and obesity has become a major problem in the U.S.

In a major US health survey, over 5,000 Americans were assessed; none had previously being diagnosed with cardiovascular disease.

Data was analysed on the 3,110 adolescents aged 12 to 19, and 2,205 adults aged 20 to 49 who took part.

The researchers led by Dr Mercedes Carnethon, say their report indicates that low fitness is a prevalent and important public health problem in the US population and a direct consequence of a decline in physical activity.

The researchers predict that the connection between low fitness and heart disease risk factors suggestes a potential rise in illness and death from chronic diseases, and is a sign of an obesity epidemic.

They are calling for campaigns along the lines of the smoking ones, in order to address the problem.

As a result of strenuous treadmill tests on 3,100 adolescents it was revealed that 34 percent were in bad physical shape and that is considered a conservative estimate as some were unable to participate because they were at risk of a heart attack during the test.

The scale of the problem was evident when one in eight adults aged 20 to 49 who performed the treadmill test were also physically unfit, say the researchers.

During the test the participants were asked to push themselves to achieve 75 percent to 90 percent of their age-predicted maximum heart rate.

It was seen that those who did poorly on the treadmill also tended to have high levels of bad cholesterol in their blood, and low levels of good cholesterol, high blood pressure and large waists, even though some of the subjects were thin.

The study found that blacks and Mexican-Americans were more likely to be unfit than whites, and more adult women were unfit than men.

The proportion was equal between teenage girls and boys.

If these results are projected onto the entire U.S. population, says the report, it suggests that as many as 7.5 million adolescents and 8.5 million adults are in bad physical shape and at risk for cardiovascular disease and other illnesses such as diabetes.

Obesity experts in Britain say they are not surprised and the study is further proof of people doing too little exercise, and warn a similar picture is already emerging there, where around two thirds of men and over half of women are overweight or obese.

They advise that healthy eating habits need to be combined with increased activity levels.

The study is published in the Journal of the American Medical Association.

http://www.medschool.northwestern.edu