Don't just sit there! The benefits of breaking up sedentary time

I've written before (here and here) about some of the research that's been demonstrating the importance of avoiding long stretches of sedentary time. (The Sedentary Behavior Research Network has proposed that "sedentary" refer to waking time spent sitting or lying down and expending little energy, while "inactive" refer to people with low levels of overall activity, and I'm using those definitions.) Some of us may feel virtuous for meeting CDC's physical activity guidelines through regular workout sessions, but bouts of aerobic exercise can't completely offset the toll of too much time spent sitting in front of a computer or lolling on the couch.

Last week, Gretchen Reynolds' New York Times piece "Stand up for Fitness" summarized some of the recent research on the importance of breaking up sitting time and offered a few commonsense suggestions for increasing physical activity in an office environment: stand up to read printed documents (Reynolds puts papers on a music stand), and pace while talking on the phone. And if you need more motivation to get up and move around a bit more, Travis Saunders at Obesity Panacea explains two recent studies that suggest occasional, low-intensity walk breaks can have metabolic benefits.

In both studies, subjects had their blood glucose concentrations measured at regular intervals following a meal. Subjects were divided into three groups: one that remained seated during and after the meal, another that performed light-intensity activity after eating, and a third that performed high-intensity activity. Saunders explains what researchers might expect to see in response to the food given to one group of participants (which he likens to a McDonald's milkshake):

This sort of drink will produce a spike in insulin and glucose levels in the blood, but a healthier person will have a lower spike than an unhealthy person. A big spike in glucose or insulin levels suggests that your body has to work harder to get sugar into your muscles, which is a sign of insulin resistance and a risk factor for diabetes.

In both studies, the active subjects' glycemic responses were substantially better than those of the sedentary subjects. (Read the whole Obesity Panacea post for a more in-depth explanation and some visuals.) And the activity levels of the light-intensity activity groups weren't very high: In one study (Dunstan et al in Diabetes Care) the subjects did light-intensity walking for two minutes out of every 20, and in the other (Nygaard et al in Applied Physiology, Nutrition and Metabolism) they walked slowly for 15 minutes.

So, if you can stand up and walk around for two minutes a couple of times an hour, and/or take a 15-minute stroll after eating, you might get metabolic benefits that can reduce your risk of diabetes and cardiovascular disease.

For many of us, it's not too hard to make such modifications. Bus and truck drivers, call-center employees, and people stuck in cars for long commutes may find it hard to avoid sitting for long stretches, though. As we design workplaces and jobs and think about how we're going to get from one place to another, it's important to remember that encouraging a little more physical activity can earn important health payoffs.