A new study has shown that teenage boys who watch television and play computer games in place of doing exercise are almost three times more at risk of having diabetes.

University of Sydney researcher Dr Louise Hardy and fellow workers collected blood samples from 500 Sydney Year 10 students.

They discovered that boys who had more than the recommended maximum two hours of 'screen time' a day were far more susceptible to developing insulin resistance, a precursor to type-2 diabetes.

The survey discovered an alarming 90% of boys and 75% of girls surpassed the two-hour guideline.

Hardy stated that surveyed teenage boys spent around 22 hours glued to their TV sets and PCs every week.

While boys were the worst offenders, Hardy said girls were catching up.

Hardy will present her discoveries by the coming week at the International Congress of Obesity in Sweden. (With Inputs from Agencies)