Almost 10 years after the triumphant birth of the cartoon Teletubbies, scientists have proved that the fat little creatures exist in real life.

The first research into TV and pre-school obesity has nailed under-fours' increasingly common girdle of unwanted fat firmly on the growing practice of giving toddlers their own bedroom TVs.

Almost 3,000 roly-polys aged under five were interviewed in the United States, where the "square-eyed bedsitter" is an increasingly popular way of keeping small children quiet. Comparative studies were made with obese teenagers and adults, whose weight gain has already been linked to couch potatodom.

The study by Columbia University and a New York healthcare institute found that 40% of the children - including all the chubbiest - already had their own bedroom TVs. Overall, they heavily outweighed the rest of the sample who did not have a bedroom set.

The study warns that peer pressure is certain to increase the problem, which is likely to affect Europe too. The survey also found that, like the Jesuits, a bedroom TV which gets a child before five, wins allegiance for life.

Viewing by the bedroom sample as they got older increased significantly faster than among the rest of the children monitored by the researchers.

The report, published today in the American Journal of Paediatrics, concludes: "A TV in the child's bedroom is the strongest marker of increased risk of being overweight. Because most children watch TV by age two, educational efforts about limiting child TV/video viewing and keeping the TV out of the child's bedroom need to begin before then."

The following correction was printed in the Guardian's Corrections and Clarifications column, Monday June 10 2002

We referred to the triumphant birth almost 10 years ago of the Teletubbies "cartoon". Teletubbies is a children's play programme, not a cartoon. It dates from 1997.