The study, published in The Journals of Gerontology, asked overweight patients with prediabetes to reduce their daily steps to no more than 1,000 a day for two weeks.
Prediabetes means your blood sugar level is higher than normal but not yet high enough for you to be diagnosed with the disease.
This period of reduced activity resulted in elevated blood sugar levels and sped the onset of type 2 diabetes.
After resuming normal activity, some patients still did not fully recover.
“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 Chris McGlory, lead author of the study.
The results suggest that older people who become inactive due to illness, bed rest or hospitalisation are more likely to suffer harmful health effects.
“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.