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Dear Doctor: I’m 35 years old and a regular exerciser. Sometimes, though, when I’m on vacation or just want to veg out, I need a break. Now I’m hearing that this is really bad for your metabolism, especially as you get older. Seriously? Taking a couple of weeks off really makes that much difference?

Dear Reader: We’re sorry to rain on your hammock time, but the newest research suggests that yes, taking as little as a two-week break from your regular exercise routine has negative health effects for older adults that can be long-lasting. This new insight comes from two recent studies that looked at what happened when physically active adults stopped exercising, even for a short time. Among the ill effects was a rise in blood sugar levels, a drop in insulin sensitivity and weight gain. As though that wasn’t enough bad news, it turned out that even after the study participants returned to their regular exercise regimens, the metabolic changes were slow to fully reverse.

A study conducted by researchers from the University of Liverpool in England looked at a group of 45 men and women between the ages of 24 and 50 who were quite active. They each walked more than 10,000 steps per day, did not have diabetes and were metabolically fit. When the study participants were asked to suddenly cut down on their exercise and begin sitting for at least 3 1/2 hours per day, their metabolisms changed. Over the course of the two weeks that the participants slowed down — their activity monitors logged under 2,000 steps per day — their blood sugar spiked, they showed signs of insulin resistance, and their blood lipid results started to become distinctly less healthy. Not only did they lose muscle mass in their legs, they gained fat around their middles. Although most of them recovered their lost ground when they began to exercise again, several of the participants showed ongoing signs of insulin resistance.

A second study from Canada’s McMaster University focused on adults aged 65 and older. In that study, the participants were also active, walking between 7,000 and 8,000 steps per day. However, in this case, they all had elevated blood sugar levels, which put them at risk of developing Type 2 diabetes. As with the Liverpool study, these adults were asked to drastically reduce their activity levels to below 1,000 steps per day, and to spend several hours sitting.

They suffered the same ill-effects as their younger peers, but more quickly and more severely. In fact, the sudden lack of exercise pushed some participants dangerously close to developing Type 2 diabetes, and they had to stop their participation in the study. Another difference between this group and the younger participants is that even after resuming normal activity for two weeks, most had not made up the metabolic ground lost to their enforced inactivity.

Yes, these are small studies, and more research is needed. But based on conclusions thus far, it appears that when we stop being active for weeks at a time, we pay a significant price.

(Send your questions to, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)