By Kerry Grens
NEW YORK (Reuters Health) Mar 09 – Taking a break to walk around every 20 minutes, instead of staying seated for hours, helps reduce glucose and insulin levels after eating, a new study shows.
“What’s shocking to me with these studies is not how good breaks are but how bad sitting is,” said Dr. Barry Braun of the University of Massachusetts in Amherst, who was not involved in the research.
The new study, published February 28 in Diabetes Care, is the latest to highlight the hazards of spending long periods being physically passive, whether it’s slouching in front of a TV or working behind a computer screen.
Dr. David Dunstan of Baker IDI Heart and Diabetes Institute in Melbourne, Australia, and his colleagues have reported previously that people who watch more than four hours of TV a day are likely to die earlier (see Reuters report of January 11, 2010).
They didn’t prove that sitting was to blame, so to explore what sitting actually does to the body, this time they experimented with how prolonged sitting could affect responses to food.
The group took 19 overweight adults who didn’t exercise much and asked them to sit for seven hours while having their glucose and insulin levels sampled hourly. After the first two hours, the participants drank a 763-calorie drink high in sugar and fat, then sat for another five hours.
Each person went through three days of experiments, each day spaced out by a week or two. One day, they sat the entire time, reading, watching TV or working on a computer, only taking breaks to use the bathroom. On another day, they took two-minute breaks to leisurely walk around every twenty minutes following the drink. And on another day they took similar breaks, but with more vigorous activity.
When they sat without interruption, their blood sugar spiked within an hour of the drink from about 90 mg/dL to about 144 mg/dL. But when they got up every 20 minutes, blood glucose rose from 90 mg/dL to only about 126 mg/dL.
Overall, getting up and engaging in light activity reduced the total rise in glucose by an average of 24%, compared to uninterrupted sitting. The difference was almost 30% with moderate-intensity activity.
The results were similar for insulin — levels peaked about two hours after the drink, but they rose higher when the people continued sitting than when they moved about.
“Their results are exactly what I would have hoped to see and what I would have expected to see,” said Dr. Alpa Patel, a researcher at the American Cancer Society. She said experiments in animals have also shown that taking breaks from sitting can have “a considerable amount of metabolic benefits.”
Dr. Braun said he was surprised that the breaks involving more intense exercise showed nearly the same benefits as the breaks to walk around.
Still, he thinks it’s pretty clear how just getting up would help lower glucose and insulin.”We know muscle contractions help take up glucose into the muscle,” Dr. Braun said. Less glucose translates into less insulin.
What’s not clear is whether reduction in glucose and insulin levels seen in this study will actually translate into health benefits.
“This was only studied over one day,” said Dr. Dunstan. “The next question is, can that reduction be (achieved regularly) and translate to reductions in atherosclerosis?”
His group is working on a longer, three-day sitting experiment.
Dr. Braun said a good rule of thumb is to try to get up about every 15 minutes, even if it’s just to walk around the room.
The Centers for Disease Control and Prevention recommend that most adults get 150 minutes of moderate exercise each week.
Dr. Patel said sitting can still have detrimental effects on people who exercise if they’re the “active couch potato” type — taking time to work out, but still spending hours and hours a day sitting.
“Break up sitting time wherever and whenever possible,” she said.
Diabetes Care 2012.