Sitting less linked to lower risk of diabetes

(Reuters Health) - People who spend time walking or even just standing instead of sitting down may be at lower risk of diabetes, a UK study suggests.

A man uses his phone while riding the subway in New York, U.S., August 24, 2016. REUTERS/Lucas Jackson

Previous research has linked sedentary time to type 2 diabetes, which is tied to aging and obesity and happens when the body can’t properly use insulin to convert blood sugar into energy.

For the current study, researchers asked 435 adults at risk for developing diabetes to wear activity monitors around the clock for one week to see how much time they spent sitting, standing and walking. Then they examined lab tests to see how well their bodies processed sugar and insulin.

Findings from this study “provide further encouraging evidence” that simply substituting standing for sitting throughout the day may improve markers of type 2 diabetes, said study co-author Dr. Joseph Henson, a diabetes researcher at the University of Leicester.

“However, stronger associations were observed for stepping, thus highlighting the continued importance of more intense physical activity,” Henson said by email.

Study participants were 67 years old on average. Most of them had excess fat around the midsection and were either overweight or obese, and about one third had a family history of diabetes.

Each day, participants spent an average of 9.4 hours sitting or lying down during their waking hours. This included a total of about 4.2 hours of brief periods of sitting for no more than a half hour, as well as 5.4 hours of prolonged bouts of sitting that lasted at least 30 minutes.

In addition, participants typically spent an average of 4.5 hours a day standing and 1.7 hours a day walking.

People who replaced 30 minutes of prolonged sitting time with shorter bouts of sitting had a 4 percent reduction in fasting insulin levels, researchers calculated.

If participants replaced prolonged sitting with standing, however, they had 5 percent drop in fasting insulin levels, and walking instead was associated with an 11 percent difference, researchers report in BMJ Open.

The study didn’t find an association between blood sugar or insulin levels when people swapped short periods of sitting for standing, however. Stepping instead of sitting for short periods was linked to a 7 percent drop in fasting insulin.

The study wasn’t a controlled experiment and can’t prove how different activity levels directly influence the risk of diabetes, the authors note. Researchers also used statistical models to estimate how much changes in activity might impact blood sugar and insulin.

Still, the results add to a growing body of evidence suggesting that even small reductions in sedentary time may help lower the risk of diabetes, said Bethany Barone Gibbs, a researcher at the University of Pittsburgh who wasn’t involved in the study.

“Breaking up prolonged sitting with walking or standing can improve how our body takes up blood glucose,” Barone Gibbs said by email.

When the body moves, it signals muscles and cells that will need fuel and they start absorbing sugar from the blood. When people are sedentary, these signals don’t go out.

“This is why blood sugar seems to go higher if we engage in prolonged sitting versus more active behaviors after eating,” Barone Gibbs added. “If we are constantly exposed to high blood sugar over time, this can cause diabetes and cardiovascular diseases to develop.”

Even though the results mirror other studies linking reduced sedentary time to a lower diabetes risk, the use of statistical models rather than a controlled experiment makes it hard to see what would happen if people cut back on sitting in real life, said Peter Katzmarzyk of the Pennington Biomedical Research Center in Baton Rouge, Louisiana.

“The people didn’t actually replace their sitting with physical activity, which is what would happen in an intervention,” Katzmarzyk, who wasn’t involved in the study, added by email. “We need more actual interventions for us to better understand what is going on.”

SOURCE: BMJ Open, January 1, 2017.