Youngsters who look at screens for more than three hours a day are fatter and have greater insulin resistance, a study found.
The findings applied to TV, tablets, mobile phones and computers, suggesting millions of children are at risk.
Under-fives in Britain spend four hours and 11 minutes on average in front of electronic screens. Children aged five to 15 spend five hours and 33 minutes a day gazing at gadgets, according to communications watchdog Ofcom.
There are four million people with diabetes in the UK, which costs the NHS nearly £10billion a year.
Type 1 diabetes is not affected by lifestyle and is not preventable.
Type 2 usually occurs when fat content in the body becomes so high that it stops insulin maintaining a normal blood glucose level. This often happens when someone has been overweight for a long time, which is why it usually does not strike until middle age.
Diagnosis of diabetes has risen by 60 per cent in a decade. To explore the increase, experts monitored 4,500 children aged nine and ten at London primary schools.
Those with more than three hours’ screen time a day were already showing warning signs of type two diabetes, according to the study published in the Archives of Disease in Childhood journal. Compared with those who spent less than an hour a day in front of screens, they had 3.3 per cent more body fat and 10.5 per cent higher insulin resistance.
The researchers wrote: ‘Our findings suggest that reducing screen time may be beneficial in reducing type 2 diabetes risk factors, in both boys and girls and in different ethnic groups from an early age. This is particularly relevant, given rising levels of type 2 diabetes, the early emergence of type 2 diabetes risk, and recent trends suggesting that screen time related activities are increasing.’
Dan Howarth, head of care at Diabetes UK, said type 2 diabetes in children is increasing at an alarming rate and should be of concern to everyone.
He said: ‘As a nation, we should all encourage physical activity rather than a sedentary lifestyle for children and adults alike.