IT’S WORSE WHEN YOU’RE OLDER: Take a Vacation From Exercise? Your Body May Not Thank You.

In some past studies with healthy, active young people, often college students, the consequences have been swift but reversible. When these volunteers have taken to their beds and chairs for days on end in the interest of science, they often have developed heightened blood sugar and some early symptoms of insulin resistance.

But within a day or two of returning to their normal activities, their metabolisms usually stabilized and blood sugar and insulin levels dropped.

Many of us, though, are not robust, young college students, and whether the impacts of becoming inactive, even for a short period of time, are likely to be as ephemeral for us has been less clear. . . .

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.

Hmm.