A short stretch of inactivity can unleash diabetes in older adults at risk for the blood-sugar disease, a new study finds.

For the study, overweight patients with prediabetes were asked to reduce their daily steps to no more than 1,000 a day for two weeks.

This short stretch of reduced activity led to elevated blood sugar levels and sped onset of type 2 diabetes -- and some patients did not fully recover even after resuming normal activity, according to the Canadian study. It was published online recently in The Journals of Gerontology.

"We expected to find that the study participants would become diabetic, but we were surprised to see that they didn't revert back to their healthier state when they returned to normal activity," said lead author Chris McGlory.

He is a research fellow in the department of kinesiology at McMaster University, in Hamilton, Ontario.

The findings suggest seniors who become inactive due to illness, bed rest or hospitalization are more likely to suffer harmful health effects.

"Treatment of type 2 diabetes is expensive and often complicated," study co-author Stuart Phillips said in a university news release. Phillips is a professor in the department of kinesiology.

"If people are going to be off their feet for an extended period they need to work actively to recover their ability to handle blood sugar," he said.

More than 84 million Americans have prediabetes, and more than 30 million are diabetic, according to the U.S. Centers for Disease Control and Prevention.

"In order for prediabetic older adults to recover metabolic health and prevent further declines from periods of inactivity, strategies such as active rehabilitation, dietary changes and perhaps medication might be useful," McGlory said.