The study, published in the journal Diabetes Care, is part of a growing body of evidence that for people who get very little exercise, "even small amounts of activity will provide a really good return on their investment," said Catrine Tudor-Locke, who studies walking and health at Pennington Biomedical Research Center in Baton Rouge, Louisiana, and was not involved in the research.

Daily walking recommendations typically point to a minimum of 10,000 steps per day. Tudor-Locke said a good rule of thumb is that 2,000 steps equals about one mile.

Earlier studies, based on questionnaires, have shown that walking more is tied to a lower risk of diabetes. But few studies have used precise measures of how many steps people take each day, said Amanda Fretts, the lead author of the new report and a researcher at the University of Washington in Seattle.

To get a better sense of walking's potential benefits, Fretts and her colleagues asked more than 1,800 people to wear a pedometer on their hip for a week to tally the number of steps they typically took each day.

All of them came from native American communities in Arizona, Oklahoma and North and South Dakota that are known to have low physical activity levels and high rates of diabetes.

About a quarter of the group were considered to have very low activity, taking fewer than 3,500 steps a day, while half took fewer than 7,800 steps per day.

At the beginning of the study, none of the participants had diabetes. But after five years of follow-up, 243 people had developed the condition.

About 17 percent of the people in the lowest activity group developed diabetes, compared to 12 percent of the people who took more than 3,500 steps a day.

After taking into account people's age, whether they smoked and other diabetes risk factors, Fretts's team determined that people who walked the most were 29 percent less likely to develop diabetes than those who walked the least.

"Our finding wasn't surprising given that other studies have shown that even light activity is associated with a lower risk of diabetes," Fretts wrote in an email to Reuters Health.

The findings don't prove that walking more is responsible for the lower risk of diabetes, but Fretts offered some possible explanations for how walking might help.

"Increased physical activity may prevent weight gain and promote weight loss, a major determinant of diabetes risk," she told Reuters Health.

Indeed, when Fretts took into account how large people were, based on a measure called body mass index (BMI), she found that extra walking didn't provide any benefits to reducing people's diabetes risk.

"BMI is one of the plausible biological mechanisms by which physical activity (or walking) may lower diabetes risk - that is, walking may promote weight loss - and weight loss is a major factor related to diabetes risk," Fretts said.

Physical activity also has effects on inflammation, glucose and other molecules in the body that could help lower diabetes risk, said Fretts.

Tudor-Locke added that the potential benefits of moderate levels of walking are "only for those who are really inactive to begin with" and don't mean others should decrease their activity levels.

SOURCE: bit.ly/Lr2Pkb Diabetes Care, online June 20, 2012.

(This story corrects attribution in last paragraph)

• A Permanent Economic Emergency