The goal is to motivate the young people to walk at least 10,000 steps a day in line with the U.S. Surgeon General's recommendation of 30 minutes of moderate exercise five days a week.
More than half the adult population in Colorado is obese and 20 percent of the state's children should lose weight, health officials said. Childhood obesity has gone up 11 percent nationwide since 1994.
Pedometers are instruments that record the distance a person covers on foot by responding to the body's motion at each step.
"It appears with a pedometer, people are more likely to stick with exercising and stick with walking," said Lee Stiffler-Meyer of the Colorado Department of Public Health and Environment. "Most kids aren't doing that."
Doctors and pediatric psychiatrists say the problem of childhood obesity is complicated and can't be blamed just on video games or the prevalence of fast food in middle and high schools.
Some cite a growing fear by parents that walking to and from school, even just a few blocks, isn't safe anymore. Others blame more rigorous academic loads, which robs time from after-school sports, or even the lack of home-cooked meals.
"There is unprecedented access to food by children and more money to buy it," said Dr. Nancy Krebs, a pediatrician who runs an obesity clinic at Children's Hospital in Denver. "And the frequency of eating out is another factor. There would be excessive intakes via excessive portion sizes."
State officials aren't yet sure which schools will get the pedometers or how old the test group will be.
The program is being launched with federal funding.