During the study, the volunteers simply stopped moving much, cutting their daily steps to below 2,000 and sitting for more than three and a half additional hours each day, a routine that they continued for two weeks.

The researchers then rechecked their metabolisms and body compositions and asked them to return to their former activity levels for another two weeks, after which the tests were repeated.

The results proved to be consistent if worrisome. The volunteers almost all had developed what the scientists called “metabolic derangements” during their two weeks of being still. Their blood sugar levels had risen, insulin sensitivity declined, cholesterol profiles become less healthy, and they had lost a little muscle mass in their legs while gaining fat around their abdomens.

Thankfully, most of these derangements were reversed once the men and women became active again.

But for unknown reasons, a few of the volunteers did not return to quite the same level of exercise they had engaged in before. They now completed fewer minutes of vigorous activity each week than previously and had some slight but lasting symptoms of insulin resistance, even after two weeks of moving normally.

The consequences of sudden inactivity were more severe and, in their way, poignant in the other new study, which was published in July in The Journals of Gerontology.

It focused on overweight people past age 65 who already were at risk of developing diabetes because they had high blood sugar. But they otherwise were healthy and active, walking about 7,000 or 8,000 steps each day.

Now, as in the other study, they sat, reducing their steps to below 1,000 a day for two weeks, after which, for a final two weeks, they moved about normally.