Taking a break to walk around every 20 minutes, instead of staying seated for hours on end, helps reduce the body's levels of glucose and insulin after eating, according to a new study.
While the latest results don't show whether these reductions have any lasting health benefits, experiencing large glucose and insulin spikes following a meal is tied to a greater risk of heart disease and diabetes. "What's shocking to me with these studies is not how good breaks are but how bad sitting is," said Barry Braun, a professor at the University of Massachusetts in Amherst, who was not involved in the research.
The new study, published in the journal Diabetes Care, is the latest to highlight the hazards of spending long periods being physically passive, whether it's zoning out in front of a TV or working behind a computer screen.
David Dunstan, a professor at 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 have an earlier death.
They didn't prove that sitting was to blame for the shorter lives, so to explore what sitting actually does to the body, Dunstan's group this time experimented with how prolonged sitting could affect responses to food. After a meal, glucose levels in the blood go up, followed by a rise in insulin, which helps body cells use that blood sugar for energy or store it, so levels in the bloodstream start to go down. In people with type 2 diabetes, this process falls out of whack - usually because the body no longer responds to insulin properly. After a meal, blood sugar and insulin levels spike and remain high. "What we have at the present is consensus ... that we should be looking at ways to minimize that exaggerated response (of insulin and glucose) after meals," said Dunstan.
His group took 19 overweight adults who didn't exercise much and asked them to come into a laboratory and sit for seven hours while having their blood sugar 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.
On 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 broke up the sitting session and took a two-minute break to leisurely walk around every twenty minutes following the drink.
And on another day they took similar breaks, but with more vigorous activity. The days when people sat without interruption resulted in a spike in blood sugar within an hour of the drink from about 90 milligrams per deciliter (mg/dl) to about 144 mg/dl.
On days when people were able to get up every 20 minutes, blood sugar 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 percent, compared to the group that kept sitting. That difference was almost 30 percent 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.
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