According to a large Swedish study, adolescents with disabilities and / or obesity have a higher probability of contracting a chronic illness and disability.

The researchers followed more than one million boys for an average of 28 years, starting at the age of 16 to 19 years.

Those who were inactive, obese or both in adolescence were more likely to receive a medical disability pension in adulthood. Pensions are granted in some countries to working-age adults who are unable to work due to a chronic illness or injury.

"Cardiorespiratory fitness and obesity as early as adolescence are closely related to future health," said lead researcher Pontus Henriksson, a dietitian at the Karolinska Institute in Huddinge, Sweden.

His team warned that this study did not prove that being unfit or obese in adolescence was the cause of disability in adulthood, but only that the two seemed linked.

This association is important though as many teens are less fit and weigh more than previous generations, said Henriksson. The study also provides more evidence of the relevance of physical fitness and obesity in adolescence as markers of future health.

The study found that men with morbid obesity were the most exposed.

Henriksson and his colleagues also found that, compared to an inability, a moderate or high physical condition was related to a reduction in the risk of disability, whether obese or not.

The researchers found that common deficiencies associated with poor physical fitness included muscular problems and debilitating injuries, diseases of the nervous system, circulatory problems and tumors, as well as mental problems.

"We need to step up our efforts to promote physical activity and prevent obesity as early as childhood," said Henriksson.

Dr. David Katz, director of the Yale-Griffin Prevention Research Center in New Haven, Connecticut, reviewed the results.

"In preventive medicine, we regularly report that it's never too late to take steps to protect your health," he said. "This paper reminds us that it's never too early either."

And while this study has only shown an association between early inactivity and subsequent disability, there is ample evidence to suggest that this trend is causal, Katz said.

Being active and managing your weight can be a healthy activity that parents and children can share, he said.

"Parents and children who are not yet engaged in health research have every reason to make the change," said Katz.

"We all want the people we love to be healthy and vital, parents can help their kids get there, and kids can help their parents." Health, just like love, is for sharing, "he said.

The report was published Feb. 11 in the Annals of Internal Medicine.