How do you move TV-watching kids off the sofa?

Parents may have a way to budge their chip-chomping, TV-watching kids from the family sofa: a bicycle hooked up electrically to the set. To see their favorite shows, couch potatoes have to pedal.

An obesity researcher who came up with the "TVcycle" says early tryouts helped youngsters shed fat and discouraged TV viewing.

David Allison of St. Luke's-Roosevelt Hospital in New York knows parents are not going to race to rewire TV sets and he cautions that his findings are preliminary.

But he says his small study of a few overweight New York children is important because it suggests tinkering with the technology that makes life more comfortable -- but also more sedentary and fattening -- could help trim Americans' expanding waistlines.

"I am not naive enough to think we're going to solve the world's obesity problems with TVs hooked to bicycles," Allison said. "But there are other things we could do ... that are limited only by our imaginations."

The National Institutes of Health says about 55 percent of American adults are overweight or obese, up from 43 percent in 1960. Studies also suggest more than 13 percent of youngsters ages 6 through 17 are overweight, and getting fatter each year.

Lack of exercise is a main cause.

Research shows television is a major culprit for kids, mesmerizing children who otherwise might burn calories while playing.

Formal exercise programs do not help much because it is hard to get to a gym or playground regularly, particularly for young children with busy parents, so scientists are hunting for home-based tricks to get kids moving, Allison said.

For his experiment, an engineer rewired TV sets to work only while the viewer was pedaling an attached bicycle. Built-in computers measure how long the televisions were on. The TVcycles, which are back in Allison's office as he hunts money for a larger study, are not for sale.

With NIH funding, Allison delivered the TVcycles to six overweight TV fans, ages 8 to 12, and put standard exercise bikes in front of televisions for four similar children.

The kids did not diet and the televisions for the TVcycle group were locked to prevent cheating.

Nobody nagged the youngsters to pedal or lose weight, Allison said. "We just said, 'Here you go. For the TV to work, you have to pedal. See ya,"' he said.

Ten weeks later, the four kids who watched television while lolling on the couch saw 20 hours a week and bicyled only 8 minutes a week, Allison said in an interview Friday before presenting his results at a biology conference Sunday in Washington.

The six TVcycle kids watched an hour a week and pedaled an hour a week. But that was not all the TVcycle kids watched.

They did not pedal when the family watched television together and there was some cheating, when parents lets kids watch a special show on a set not part of the test, Allison said.

But the pedaling kids finished the study with 2 percentage points less total body fat and 3 percentage points less fat on their legs than the other children. So those kids must have been more active during the time once spent watching TV.

"It's quite amazing they'd see any change" in such a short time and in kids who did not diet, said Michael Jacobson of the Center for Science in the Public Interest, a consumer advocacy group that fights obesity.

Allison says the study shows scientists should look for innovative ways to encourage physical activity and better nutrition.

One of his more radical suggestions is charging a quarter to ride an elevator, which might leading more people to use the stairs.