Overweight People May Benefit From Active Breaks During Prolonged Sitting

Interrupting prolonged periods of sitting with regular, two-minute breaks of light or moderate intensity activity like walking may be good for overweight and obese people’s health, because new research reported recently in Diabetes Care shows it helped their bodies keep glucose and insulin levels under control after consuming the equivalent of a high calorie meal (“postprandial” levels).

Repeated spikes in blood sugar or glucose, such as those that can occur after a meal, have been linked to poor health outcomes, including artery stiffening and cardiovascular disease. The body keeps glucose levels under control with insulin secreted from the pancreas.

Study leader Associate Professor David Dunstan, of the Baker IDI Heart and Diabetes Institute, in Melbourne, Victoria, Australia, told the press that with larger and more frequent spikes, the walls of our arteries and veins become more and more damaged.

“This increases our susceptibility to heart disease. So, we want to minimise these rises in order to improve our health outcomes,” he explained.

“Our research has already shown that sitting for long periods can be hazardous to health. Sedentary behaviour is also a risk factor for chronic diseases, including some cancers,” said Dunstan.

For their study, the researchers recruited 19 participants aged 45 to 65 who were either overweight or obese.

Each participant took part in three experiments, with six days break between each one.

In the first experiment they had to sit for 5 hours with no break. In the second experiment they sat for the same length of time, but every 20 minutes they walked on a treadmill at a light-intensity pace for 2 minutes. And in the third experiment, they did the same as the second, except the pace was at moderate intensity.

The idea was to create conditions similar to that of office workers who sit at their desks for long periods.

To provide a reliable measure of blood glucose that could be compared across all three experiments, before each experiment the participants sat for two hours, uninterrupted. Then they were given a standardized test drink containing 75g of glucose and 50g of fat (to give the digestive effect of a high calorie meal). Their glucose and insulin levels were then tested at the end of the 5 hour periods in each of the three experiments.

Dunstan said:

“In a controlled laboratory environment that mimicked the typical patterns of desk-bound office workers, participants who interrupted their sitting time with regular activity breaks, showed up to 30% improvement in the body’s response to a meal containing glucose.”

And he and his colleagues were surprised to find there was little difference in benefit between high and moderate intensity activity:

“The good news is that the improvements were seen even with light-intensity activity, which is the equivalent of strolling,” said Dunstan.

This would suggest that it is not the amount of effort involved that has an effect, but just the act of standing, moving and reducing sitting time.

Dunstan said we need to accept that our bodies are not designed for prolonged sitting. If you look back twenty years or so, even in office environments people moved around more, throughout the working day.

“Prior to email, people had to collect mail from a pigeon hole, or walk over to people’s desks for a chat. I think we’ve reached a crisis point where we need to step back and acknowledge that sitting for long periods is not what our bodies were designed for.”

“The results of this study now provide some direction about what activity can be undertaken to break up sitting time and counteract the negative effects of sitting for long periods, including the frequency of breaks required to improve health outcomes,” he added.

The benefit of frequent breaks of activity comes about because when we sit, our muscles are essentially asleep, says Dunstan. But when we are up and moving, they wake up: we contract our muscles, and this is what helps to regulate the body’s metabolic system.

The findings also bolster another Australian occupational health and safety recommendation: that employees who sit at desks and look at screens should break every 30 minutes to relieve their eyes.

Dunstan and colleagues are keen to point out that while much of their discussion is around office workers, there are many other settings where people sit for hours on end without a break, such as watching TV, playing video games, using home computers, and driving cars.

They also point out that while their participants were overweight or obese, the findings will apply to anyone who sits for long periods: they could also benefit from breaking up their sitting time.

In an office environment it is not likely that you will find a convenient treadmill but there are other ways to break up sitting time at work, such as standing up regularly, or walking to the printer, using the stairs instead of the elevator. Even standing up while you use the phone can be of benefit, said Dunstan.