Benefits of a period of exercise persist after 10 years.

Gretchen Reynolds points to a study by Johnson et al. showing long term effects of an experiment conducted from 1998 to 2003, in which overweight volunteers between 40 and 60 were divided into control (inactive), moderate walking), and vigorous (jogging) exercise groups that completed three sessions of their assigned workout each week for eight months. Health markers (aerobic fitness, blood pressure, insulin sensitivity and waist circumference) improved in the exercise but not the control groups. Experimenters were able to get in touch with many subjects 10 years later and found:

Most of the men and women from the control group, who had not exercised 10 years before, had larger waistlines now, while the exercisers displayed little if any middle-aged spread compared to their decade-earlier selves.

Those from the control group also were less fit now. Most had lost about 10 percent of their aerobic capacity, which is typical of the declines seen after about age 40, when most of us will lose about 1 percent of our fitness annually.

But those men and women who had exercised vigorously for eight months during the original experiment retained substantially more fitness. On average, their aerobic capacity had fallen by only about 5 percent, compared to when they had joined the Strride study, and those few who reported still exercising at least four times a week were more fit now than they had been a decade before.

Interestingly, those earlier experimental volunteers who had walked — meaning their exercise had been moderate, not intense — did not seem to have enjoyed the same lasting fitness benefits as those who had exercised more vigorously. Most of them had shed about 10 percent of their aerobic capacity during the past decade, much like the controls.

On the other hand, they showed surprisingly persistent improvements in their metabolic health, more so than among the intense exercisers. The walkers from 10 years ago still had healthier blood pressures and insulin sensitivity than they had had before joining the earlier experiment, even if they rarely exercised now. They had also had relatively healthier metabolisms than the men and women who had exercised intensely all those years before.